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Management of Key Cotton Arthropod Pests with Insecticides and Acaricides

By
Ian Grettenberger
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Objectives of Research

1.) Develop an expanded database on the current efficacy of labeled/recommended insecticide and acaricide products on key insect and mite pests of cotton in the San Joaquin Valley and document the influence of these products on beneficial arthropods with the objective of providing better guidelines on pesticide use.

2.) Evaluate the effectiveness of new candidate insecticide/acaricide products on key San Joaquin Valley cotton pests, the impact of these new compounds on populations of beneficial arthropods, and devise strategies for deploying these new products.

3.) Examine factors, including insecticide-related, environmental, and agronomic factors, which influence management of cotton arthropod pests with registered and experimental insecticides, emphasizing insects that threaten lint quality.

Introduction

We must maintain a multifaceted IPM approach to sustain an efficient and stable system of pest management in California cotton and to improve overall profitability. Insecticides remain a key component of effective management of arthropod pests in cotton. Furthermore, management of insect pests is a critical aspect of managing sticky cotton. California has a reputation for producing high-quality cotton, and successfully managing whiteflies and aphids and the resulting havoc they can create with lint quality is key to maintaining this reputation. Up-to-date data on insecticide efficacy are in constant demand by growers and PCAs, as are data on how given insecticides can fit within an IPM program. The results from this project will clearly be used nearly immediately.

Regulatory actions involving insecticides are ongoing and likely inevitable in California’s agricultural sector, which can lead to uncertainty and changes to what tools are available to control arthropod pests. In recent years, several insecticides, such as several organophosphates, Temik®, and endosulfan, have been lost due to marketing decisions (probably hastened by regulations). Use of several EC formulations in cotton have been limited due to VOC regulations in the SJV – dimethoate, abamectin, etc. Concerns about off-site movement (via water and air) have threatened registrations and use of chlorpyrifos and pyrethroid products (and several premixes that contain a pyrethoid). Belt® insecticide was removed from the market although it was promoted and thought to be a reduced-risk material for beet armyworm (and other species) control. Recently, numerous insecticides, especially neonicotinoid products, are being scrutinized due to the ongoing honeybee/pollinator concerns with proposed regulations potentially having significant impacts. There are a variety of neonicotinoid products used by the industry that could be influenced by future regulations. Registrations of “new” insecticide products such as Transform® are threatened and have been delayed (on again and off again) as well due to the pollinator issue. Transform will not be available for the upcoming season in California. During the last growing season, chlorpyrifos was slated from removal from the marketplace. This has clearly left a gap in tools for late-season management of aphids and whiteflies. The overall effect of the losses or lack of registrations is very problematic and makes pest management more challenging.

Products are also being removed from the “toolbox” because of the build-up of insecticide resistance in pests, which are constantly evolving. Organophosphates are typically not useful for lygus management, and pyrethroid insecticides may be useful for lygus for one application per season due to resistance. Spider mite control options have been available and numerous, but there appears to be some slippage in performance in recent years in other field crops. Given the ability of spider mites to develop resistance in multiple regions and cropping systems, this is not a surprise. Presently, whitefly control options are still in place although during some “application windows” there are now a shortage of options. Mid-season aphid management is still viable as long as the neonicotinoid products are available, but late-season there is a critical void with the loss of chlorpyrifos. Maintaining effective aphid and whitefly IPM programs is essential to addressing the threat of sticky cotton to the industry.

The challenges from development of insecticide resistance and regulatory actions are best addressed with well-planned research and interaction/collaboration with all concerned industry representatives. Fortunately, new materials are developed to facilitate IPM programs. These new products must be evaluated under California conditions. This development of new products appears to have slowed somewhat recently with the consolidation of the agrichemical industry and changes in ownership that have disrupted and delayed research plans. In the interim, available experimental products will be evaluated, registered products will be researched and evaluated for efficacy, and other IPM tactics will be studied and developed. This research has allowed and will continue to allow a thorough evaluation of the applicability of experimental materials for the California cotton system before they appear on the market. By examining the complete “big picture” of California cotton IPM, this project helps to determine the applicability and fit of these products. The pests of interest in this project include cotton aphids, spider mites, thrips, whiteflies, lepidopteran larvae, and lygus bugs. Emerging and invasive pests will also be addressed, as needed and relevant. The integration of insecticides and acaricides with other management approaches (biological control, etc.) will be emphasized.

Summary: Insecticide/Acaricide Efficacy

The research season in 2019 progressed well, despite some weather challenges early in the season that made research challenging when trying to get cotton planted, although this was something that commercial growers faced as well. Late-season rains prevented us from getting out cotton planted “on time”, especially at the Shafter Research Station. Planting at West Side Rec was less affected. Whitefly populations were low but were relatively consistent over the course of the trial. Our aphid populations steadily declined after the first application, leading to very low populations after the second application. In the past year, we continued conducting the research trials at the locations (West Side REC and Shafter Research Station) where they have been conducted for the past several years. Field and laboratory work was split between both locations, with the lygus and mite trials conducted at West Side REC and the aphid/whitefly study at Shafter Research Station.

Lygus

Objective: To evaluate Lygus bug management tactics, including newly registered insecticides, combinations of materials and varied timings, and industry standard (registered) insecticides, as well as the effect of treatments beneficial insects and secondary pest populations.

  • Application Dates:2 applications, July 9 and July 14
  • Study Location:West Side Research and Extension Center, Five Points, CA; Fresno County
  • Application Equipment: pull-behind tractor sprayer, CO2 propellant, Spraying Systems TX-VS10 nozzles (5 nozzles per row)
  • Application Parameters:20 GPA, 40 PSI, 3.5 MPH
  • Plot Size: 10 rows x 68′ feet, 4 replications
  • Plot Design: randomized complete block
  • Plot Condition:irrigated Acala cotton (PhytoGen 764 WideStrike RF) planted on 38 in rows
  • Insect Sampling: Lygus: Adults and nymphs per 50 sweeps per plot at various days after treatment (DAT). Secondary pests: 10 leaves/plot (5th main stem node leaf from top) were collected and aphids and spider mites counted in the lab 10 DAT1). Natural enemies were assessed once at 7 DAT1 using the same sweep net sampling used for lygus sampling. Later sampling using the same technique was not possible because of the growth habit of the cotton.
  • Yield: We picked the middle two rows with a commercial picker. We weighed seed cotton and calculated yield per acre, accounting for exact feet of row that were harvested.

For all results, see tables and figures for full analysis details and means.

Lygus nymphs: Pre-treatment populations of nymphs were 7.75 per 50 sweeps. At 2 DAT1, only Warrior and Vydate provided any level of control (70 and 76 percent). At 6 DAT1 Vydate provided 80 percent control, while both Transform treatments, Carbine, and Diamond+Carbine all provided 70-80 percent control. Differences were more pronounced 10 DAT1, with the same treatments (other than Transform-L) providing 80-90 percent control. Only Vydate had high levels of control 13 DAT1.

At 2 DAT2, a number of treatments had 80-90 percent control. At 6DAT2, Diamond+Carbine, Orthene, Transform (L and H) and Vydate all had 90-100 percent control. Diamond alone provided 80 percent. At 10 DAT2, only Orthene and Vydate had above 80 percent (83) control. The pattern was similar 13 DAT2 and at 21 DAT2, Diamond provided 90 percent control, Orthene 97 percent, and all remaining 51 percent and lower.

Lygus adults: At the first sampling (2 DAT1), Transform-L and Vydate provided a degree of control (70 and 80 percent). At 6 DAT2, only Transform-L provided any degree of control (75 percent). At 10 DAT2, many of the materials provided some degree of control in the 40-50 percent range, and Carbine, Diamond, Transform-H, and Warrior all provided 64 to 68 percent control. At 13 DAT1, Transform-H provided the best level of control (70 percent), with some control (54 and 59 percent) still offered by Carbine and Diamond+Carbine. 2 DAT2 Orthene provided 86 percent control. At 6 DAT2, both Transform rates provide 88 percent control. At 10 DAT2, a number of materials provide 45-60 percent control.

Natural enemies: We have not yet attempted to analyze the natural enemy data using multivariate statistics, so we present analysis of summed counts of natural enemies. At 2 DAT1, there were significant differences among treatments based on the overall analysis, but none in pairwise comparisons (numerically lowest in Belay, highest in Diamond+Carbine). At 10 DAT1, natural enemies were least abundant in the Belay and Sivanto-High treatments and highest in the Brigade and Untreated. At 13 DAT1, natural enemy populations had increased across most treatments, with the untreated having the most, followed by Brigade and Baythroid. Orthene, Assail, and Belay all still had low natural enemy populations.

Secondary pests: Aphid and mite populations were low during this trial and none of the treatments led to very high levels. Populations of aphids did differ significantly between treatments (F14,42 = 2.67, P = 0.007). At 10 DAT1 when they were assessed, aphid populations were highest in the Brigade plots (~1 per leaf), followed by Baythroid, Vydate, and then the Untreated. The only significant differences were between Baythroid and Assail, the latter which had the fewest. Mites were extremely low overall, with no significant differences among treatments (F14,42 = 0.57, P = 0.87). After the second application (6 DAT2), the untreated had the most natural enemies, followed by Vydate. Orthene, Transform-ow, and Assail all had few natural enemies. These patterns generally persisted through the end of the study. At 13 DAT2, the untreated had by far the most natural enemies, followed by Warrior and the Admire/Carbine treatment.

Yield: Yield was highest in the Vydate treatment with 3,254 pounds seed cotton per acre. This was followed by Diamond+Carbine with 3,152, Carbine with 3,093, Transform-H with 3,090. Brigade had the lowest yield at 2,015, followed by Baythroid at 2,148.

Bioassays

Similar to previous years, we have continued to monitor insecticide resistance in lygus populations for key insecticides. This includes older materials like Vydate and Capture, and newer materials that have been increasingly relied upon for lygus management, Capture and Carbine. For Vydate and Capture, these assays consisted of exposure of insects to the material in insecticide coated plastic bags. The Carbine method relies on dipped green beans, while Transform uses floral foam soaked with a solution containing the insecticide.

The data are still being processed for these assays, but we can report on the number of assays that were completed. To mirror prior years, we conducted both early and late season assays. For the early season assays, we had four locations, with insects collected between May 31 and June 13. For the late season assays, we again attempted assays at four locations, but lygus were no abundant enough for the full complement of assays. At two of the locations, we could run all four materials. At one site, we only had enough for two materials, so we focused on Carbine and Transform. At the other, site, we were unable to collect enough lygus for assays.

Aphids and Whiteflies
Objective: To compare the efficacy of selected registered insecticides and
experimental materials against cotton aphids and whiteflies during the midand
late-season period in Pima cotton.

  • Application Dates: 28 August and 11 September – Insecticides – 21 treatments
  • Study Location: Shafter Research Station near Shafter, CA; Kern County
  • Application Equipment: High-clearance trailer spryer pulled with a tractor, CO2 propellant, Spraying Systems TX-VS6 nozzles (5 nozzles per row)
  • Application Parameters: 30 GPA, 40 PSI, 3 MPH
  • Plot Size: 5 rows x ~55′ feet, 4 replications, 38 in. rows
  • Plot Design: Randomized Complete Block
  • Plot Condition: irrigated Pima cotton (‘Phytogen 841 RF’)
  • Insect Sampling: All insect data were collected from 10-leaf samples (5th main stem node leaf down from terminal) per plot. Cotton aphids (Aphis gossypii) and whitefly nymphs Bemisia tabaci Biotype B, (formerly B. argentifolii): visually counted on leaves using a dissecting microscope. Data on WF nymphs were collected per entire leaf as well as per “quarter-sized” disk (between the main leaf veins; not reported here). This is the area that the treatment threshold is based upon. Whitefly adults: leaves were carefully examined and turned over in the field and adults counted.
  • Yield: We picked the middle two rows with a commercial picker. We weighed seed cotton and calculated yield per acre, accounting for exact feet of row that were harvested. We did not harvest any plots in the first block because vigor was extremely poor, and this would have not been useful yield data. Yield was very low overall.

For all results, see tables and figures for full analysis details and means.

Aphids: On the day of application, aphids averaged 116/leaf. At 2 DAT, The low rate of Transform was most effective (91 percent control), followed by Lorsban+Dibrom and the high rate of transform. At 7 DAT1, both Transform rates performed well, with 98 and 97 percent control of the high and low rates respectively. Lorsban and Sefina-Low both provided 89 to 90-percent control. At 13 DAT1, many of the treatments provided excellent levels of control (many over 90 percent 80 percent). This included all of the newer materials (Sefina, Sivanto, Transform, PQZ, Carbine; all rates) as well as Assail, Lorsban+Dibrom, and Knack. Meanwhile, by this point, Vydate, Lorsban, and Courier had increased numbers of aphids relative to the control (numerically, not significantly different). Immediately after the 2nd application (2 DAT2), the Lorsban+Dibrom had the fewest aphids. At 7 DAT2, aphid populations in the untreated had started to crash and were only 9 per leaf. The following sampling dates were somewhat less useful because of the low untreated numbers, with one exception being that these patterns showed which treatments otherwise maintained aphid populations (see Vydate in particular).

Whitefly nymphs: On the day of applications, whitefly nymph populations were low at 0.9/leaf. At 2 DAT1, only Knack provided >50 percent control at 56 percent. At 7 DAT1, a number of the other treatments began to provide some level of control, with Sivanto-Low provided the best at 83 percent, followed by Assail+Bifenture at 76 percent. A number of other treatments provided 60 to 70 percent control. At 13 DAT1, the untreated had fairly low numbers, so percent control was poor across treatments (other than Courier). At 2 DAT2, Sivanto-High provided the best control (82 percent), followed by Assail and Sefina-High.  Lorsban provided the least level of control at this time point. At 14 DAT2, Cormoran provided the most control, followed by Assail, Carbine (although this appears to aberrant), Sefina-Low and Assail+Bifenture. Across dates, Vydate and Admire Pro performed poorly, several times having more nymphs than the untreated.

Whitefly adults: Whitefly adult counts typically ranged between 1 and 2 per leaf in the untreated over the course of the study. There were only significant differences among treatments for several of the assessment dates (7 DAT1, 2 DAT2, and 21 DAT-2 – at α = 0.10). Posthoc comparisons did not indicate any significant differences except on 7 DAT1 when the untreated was significantly different from over half of the treatments.  No individual treatment appeared to stand out when viewed across dates.

Secondary pests: Spider mites were evaluated as a secondary pest that could be flared by treatments for aphids/whiteflies. Mite counts were very low over the course of the study. We therefore analyzed counts summed by plot across the entire study. There were not significant differences among treatments for these counts (F19,57 = 1.17, P = 0.31).

Yield: Measuring yield was not one of the key aspects of this study because we are focused on managing aphids and whiteflies because of the way they threaten quality of lint (via sticky cotton) rather than quantity of lint. We did not detect significant differences in yield quantity (F19,38 = 0.41, P = 0.97).

 

Evaluation Of Effectiveness Of Varying Rates and Application Methods Using Cotton Clean ™ Technology

By
Greg Palla
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The purpose of this study was to evaluate the effectiveness of the Cotton Clean™ product when applied with various methods and at various rates. The results confirmed what our preliminary research indicated.  Generally, the study indicates that Cotton Clean™ shows significant benefit in reducing stickiness on cotton that is at a level of moderate to heavy levels of stickiness.  Where stickiness is light or nearly absent, Cotton Clean™ does not have any significant effect on reducing stickiness.  From these findings, one may conclude that where stickiness levels are very low to begin with, there may be insufficient food source (deposited insect sugar) for enzymatic sugar reduction through the use of Cotton Clean™.  Therefore, the stickiness of cotton with low levels of stickiness do not change with any degree of significance.  This is true statistically, as well as economically, as extremely low levels of stickiness generally cause no detectible difference in textile processing or quality of output.

Also, we determined cotton ginned at commercial gins where Cotton Clean™ was applied at time of ginning was significantly less sticky than cotton from the same farm that was ginned at a facility where no Cotton Clean™ was applied at time of ginning.

Introduction

Aphid and whitefly pests are well distributed throughout the San Joaquin Valley and in many other irrigated upland and pima cotton producing regions, particularly where arid conditions exist.  It is well documented that several species of these pests can deposit objectionable levels of sugars through their excreta which can make processing seed cotton (in ginning) and cotton lint (in carding and spinning) very difficult and time consuming if sugar deposits reach moderate to high levels.  Growers have used many methods and approaches in keeping sticky cotton producing pests to a manageable level, but there are instances where their efforts are ineffective in the avoidance of problematic stickiness levels.  When this occurs, gins and spinning mills have severe problems in handling cottons in this condition.

It is believed that if the deposited insect sugar was converted into a substance with little or no viscous properties at ginning or spinning operational temperatures, without harming the cotton fiber onto which it was deposited, then ginning and spinning processes would be improved and lint quality preserved.

In 2016 San Joaquin Valley Quality Cotton Growers Association began work to identify ways to combat the ill effects of sticky cotton beyond control of the insect source itself.  A biological agent was introduced on problematic seed cotton that had been plugging up stands at a roller ginning facility.  It was sprayed on seed cotton at the module feeder in an aqueous solution.  Cotton so treated did not exhibit problems with plug ups at the stands.  After that initial trial further study was conducted and it was determined that a more precise formulation could be developed to address Trehalulose and Melizitose even more effectively.  In 2017 Cotton Clean™ was developed in conjunction with the manufacturer and their principal dealer.  Cotton Clean was provided to 12 different growers for use in applying at harvest and 1 gin used the material applied at the module feeder.

Lint samples were collected from bales treated with Cotton Clean™ and those bales not treated with Cotton Clean™.  Those lint samples were tested using Thermodetector, Mini card, and Mesdan ConTest stickiness testing methods.  Most test data sets indicated reduced stickiness on samples treated with Cotton Clean™, while a few sets were more inconclusive.  Whether or not influential factors not recognized had impacted the results was unclear.  Some of those factors are the subject of this project proposal, including rates of application and methods of application.  What is known is that ginning personnel report anecdotally that there were no problems with gin stand plugging on cotton treated with Cotton Clean™, whereas, untreated cotton from the same field continued to exhibit plugging problems.

A better understanding of the proper rate of use of Cotton Clean™ and most effective method for application will help growers and ginners make the most of this contamination mitigation tool.

Methods and Materials

Plan of work:

  1. Identify sources of seed cotton to be included in the study. Growers and ginners in the San Joaquin Valley were contacted to participate as volunteers in the study.  In addition to commercial locations, research plots were used as a source of seed cotton.
    1. Cotton was collected from and ginned at:
      1. The Shafter Research Station – Farmers Co-Op Gin
      2. Armstead Ranch – Westhaven Cotton Gin
  • Woolf Farming – Huron Gin
  1. Errotabere Ranches – West Island Gin
  2. J. Polder Co. – West Island Gin
  1. Seed cotton samples (both Upland and Pima) were collected from the fields prior to harvest, identified and segregated so as to preserve identity for both test and control sample sets.
  2. Varying rates (25 to 90 bales per pound) of Cotton Clean™ were applied through picker moistener systems at time of harvest as well as varying rates applied at time of ginning.
  3. Lint samples were collected at the gins and transported to secure storage until fiber testing is conducted.
  4. Lint samples were tested for stickiness using Mesdan Contest instrumentation and recorded.
  5. Randomly selected lint samples were procured for testing at USDA ARS New Orleans for additional confirmation of results.
  6. Results were analyzed and reported.

Results

The results from this experiment generally support our hypothesis that Cotton Clean™ reduces the stickiness grades determined by the Mesdan Contest Cotton Quality Testing machine. The overall results from all stickiness levels of cotton in the experiment were slightly in favor of the sample group that had Cotton Clean™ applied. The average stickiness level of the fields without Cotton Clean™ applied during ginning was 102. The average stickiness level of the fields with Cotton Clean™ applied during ginning was 97. A difference of 5 points on the measurement system of the Mesdan Contest machine is insignificant. While it is noted that some field stickiness grade averages were higher with Cotton Clean™ applied than without, those only occurred in samples with low (<100 stickiness grade).

However, when fields with lower levels of stickiness (<100 stickiness grade) were removed from the averaging process, the result is dramatically different.  When only those fields with medium to heavy stickiness were considered, Cotton Clean™ applied at ginning reduced measured stickiness significantly, from 147 down to 97, a reduction of 34%.

In order to confirm validity of results measured by the Contest instrument, a random selection of samples from each field was sent to USDA-ARS in New Orleans for blind testing using the standard minicard stickiness test. The minicard test uses a different method of measurement to gauge stickiness levels than the Contest instrument, but has shown relatively good correlation of stickiness between the two measurement technologies.  That being said, due to the variability of stickiness among samples within a field the results may also illustrate some degree of variation. The measurements reported by USDA are None, Light, Medium, Heavy, and Very Heavy. In order to make relevant those designations to Contest values, we assigned values we believe to be consistent with similar levels of stickiness as measured by the Contest instrument.  None = 10, Light = 75, Medium = 125, Heavy = 200 and Very Heavy = 375.  We assigned a numeric value of 10 for None in order to present it graphically, but for all intents and purposes Contest levels of 0 and 10 are effectively indistinguishable.

The results by field for the samples without Cotton Clean™ applied during ginning were 4 fields were None, 10 fields were Light, and 1 field was Heavy. The results by field for the samples with Cotton Clean™ applied during ginning were 1 field was None and 14 fields were Light.  None of the samples treated with Cotton Clean™ measured above a Light designation. It should be noted that the minicard designations are subjective evaluations of the technician conducting the test.  The difference between Light and None in some instances can be almost indistinguishable.  Medium, Heavy, and Very Heavy designations tend to be much more pronounced.  So as indicated by the Chart 3, one can see that only where stickiness is more than Light, (in this case Heavy in field 18), can we see significant improvement with Cotton Clean™.  This is consistent with the results developed independently with the Contest instrument and so therefore, we conclude the independent results confirm one another.

CHART 3

Since only one commercial gin applied Cotton Clean™ uniformly on cotton of a large scale (>10,000 bales) we were only able to evaluate stickiness grades of cotton ginned commercially at one rate (80 bales ginned per pound of Cotton Clean™ applied).  At this rate stickiness grades averaged 32 versus an average of 58 for those bales ginned from the same farm but ginned at a ginning facility that did not use Cotton Clean™.  Even though all the stickiness levels in this instance were not considered heavily sticky, this large scale test from a farm producing > 10,000 bales indicated that stickiness grades were significantly reduced when Cotton Clean™ was applied at the time of ginning.

Conclusion

Cotton Clean™ shows significant benefit in reducing measured stickiness in instances where stickiness levels in the field are expected to be medium or moderate levels and above. Even when cotton stickiness levels are below moderate, proper application of Cotton Clean™ at manufacturers suggested rates at time of ginning shows significant reduction in measured stickiness.

Acknowledgements

This study could not have been conducted without the assistance and cooperation of many individuals and organizations.  We wish to thank all who contributed something to this effort, especially the following:  Armstead Ranch, California Cotton Ginners and Growers Association, California State University, Bakersfield, Errotabere Ranches, J. Polder Co., Stone Land Co., USDA ARS New Orleans, Westhaven Cotton Co., and Woolf Farming Co.

 

 

Assessment of Fusarium in SJV Cotton: Field Evaluation Support, Identification and Commercial Variety Screening Evaluations

By
Bob Hutmacher
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This project covers two primary purposes: 1) Conduct germplasm screening trials of commercially-available cultivars plus evaluations of experimental cultivars seed companies submit to us for FOV resistance evaluations.  In these evaluations, all entries in all University of CA variety trials (Acala/Upland, Upland Advanced Strains, Pima, Pima experimental cultivars, National Standards trials) are included, plus experimental entries submitted by seed company breeders. 2) Support field efforts to collect samples and evaluate fields to determine and characterize the race of Fusarium (race 4 or others) in SJV cotton fields when growers, seed company reps or consultants contact us for assistance with plant evaluations and fusarium race identification.

Prior and Current Work

Resistance Screening Work – Commercially Released Cultivars and Company Experimentals. This work has been directed toward identification of relative levels of resistance/susceptibility to race 4 FOV, including both indices of severity of disease impacts and survival under moderate to severe FOV race 4 pressure, with focus on evaluations of newer experimental and commercially-available cultivars. The two objectives mentioned above are at least somewhat related, as we conduct field trials to evaluate germplasm resistance to FOV, and we need to identify and access fields and cooperative growers if field screening trials are to be conducted.

Field evaluations in the resistance screening program each of the years of the trials have included:

  1. Commercially-available germplasm of Pima varieties included in our variety trials
  2. Commercially available germplasm of CA Upland and any remaining Acala varieties included in our variety trials,
  3. Experimental germplasm from company commercial development and improvement programs, plus
  4. Entries from cotton breeders at a variety of locations, including those from the RBTN tests done nationwide, plus efforts will be made to solicit entries from private company breeders working with Pima or hybrids (we have some funding through Cotton Incorporated CORE that helps cover some of the costs for the other agronomic evaluations (yield, fiber quality) for the Regional Breeder entries from U.S. public breeders – but the costs of the FOV race 4 screening work are not provided by that funding)

Field Sample Evaluations Work

Some support has been utilized to facilitate travel to field sites and allow us to be in the fields to physically do the visual surveys and collect samples, and to provide county and UC support for repeated trips to screening sites/fields as well as to grower fields where the Principal Investigator for this study gets requests for field evaluations to assess presence of Fusarium race 4.  Efforts beginning in 2002 and continuing through current efforts have been in repeated field visits to grower field sites, collection and evaluation of stem and hypocotyl samples for evidence of vascular staining, and AgDia test evaluations when growers/consultants make the request for Fusarium race identification.

The varieties tested include all commercial and public breeder entries in our variety trial program plus company/breeder submitted experimental cultivars. This screening effort is separate from, and in addition to, the work covered in a separate breeding program effort supported through cotton industry funding for a project entitled  “FOV race 4 Germplasm Development” that in recent years has been jointly funded by CA Cotton Alliance and CA Cotton Growers Association Research Funds. That project is a cooperative project with Dr. Mauricio Ulloa of USDA-ARS in Lubbock, Texas.  The cooperative work with Dr. Ulloa is somewhat different from the screening efforts supported by this proposal in that this project is more focused on maintaining: (a) support for FOV race 4 resistance screening for commercial entry commercial and experimental entries, plus entries from public breeders; and (b) some funds to continue support for field race 4 evaluations requested from growers, consultants and seed companies for which we need to purchase AgDia test kits and cover related other expenses.

Field Sample Evaluations

Since 2013, we have been using the AgDia company race 4 FOV quick test on root and lower stem samples in these field evaluations.  For some FOV race identification pathology work for samples when we request additional evaluations over and above what can be done using the AgDia quick tests, we are working with Dr. Maggie Ellis at CSU Fresno to determine local capabilities for identification of other races of FOV if that becomes necessary and useful. The funds from this proposal/project help provide funds to purchase the FOV-4 AgDia kits, which cost approximately $35 for each sample run (just for the supplies, not other lab costs or staff time).

Summary Report of 2018-19 Activities

For 2019, sites for field evaluations and sampling were located in 4 cotton producing San Joaquin Valley counties  (Fresno, Merced, Kings, Tulare Counties), with the most new confirmed sites located in Merced County. There were 27 fields visited and evaluated visually for FOV4 evaluation, and sampling for Fusarium race 4 done in 19 fields, and confirmations of FOV4 in 16 of the fields visited. Unless we see significant increases in different variants of FOV (race 4, others) in cotton, we expect a downward trend in requests for field visits to continue in the next years.

The number of requests for field evaluations compares with sampling in earlier years: (1) 2018—48 fields evaluated, with 37 confirmed as race 4 FOV; (2) 2017—66 fields evaluated; (3) 2016—89 fields evaluated; (4) 2015—89 fields were visited for in-field evaluations, with AgDia tests run on 47, and 21 positive determinations in tests for race 4.  These numbers most likely do not represent the full number of additional fields that could have been identified as race 4 FOV, as some fields were visited where samples were not collected due to lack of grower desire or approval to collect samples needed to provide an assessment.

Results 2019 – Field Resistance Screening Evaluations

Field varietal screens were planted and completed at both field screening sites at the time of this report, both in fields confirmed to be infested with FOV race 4.  The field tests were done only in a part of the field where a prior cotton crop showed consistent, significant plant losses due to FOV race 4 (greater than 50 percent mortality in susceptible Pima entries). An initial plant population count was done within 2 weeks after planting in plots at both sites, followed by plant survival counts done a minimum of two times during an evaluation period of 7 to 8 weeks after emergence of cultivars being tested for resistance at the Tulare County site and a Dos Palos area (Merced County) site.

In addition to plant survival percentages, we evaluated plants for root vascular staining, foliar damage index rating, and plant size / height and node counts as a measure of vigor. At both sites, major hand weeding efforts were required to keep weeds under control in these sites due to restricted use of herbicides necessitated by working with conventional cotton varieties.

The commercial varieties and company and RBTN program breeder experimental materials evaluated in our Commercial Entry and Company/RBTN Experimentals screening trials for 2019 are shown in the following figures in this report.  Average root vascular stain values for the TULARE COUNTY SITE are the only 2019 date summaries available and ready to share at the time of preparation of this report. Data analyses on the rest of the data sets are underway and will be made available to seed companies, breeders and industry partners in the fall.

The following tables (Figures 1-4) show the average Root vascular stain index ratings for all of the Pima and Upland cotton entries in the commercial screening trial for FOV-4 resistance conducted at the Tulare County site in 2019.  As with prior years, check varieties are included in the screen: more susceptible varieties such as DP-340 and DP-744 Pima, and some more highly resistant commercial Pima varieties such as Phy 888RF, Phy 841 RF, DP 348 RF, DP 359 RF and others). Also included in this screen are all varieties entered in the following variety trials for 2019:  CA Uplands/Acala trial, CA Uplands Advanced Strains trial, National Standards Uplands trial, Pima variety trial, and RBTN (Regional Breeder Testing Network) entries.

Other than the previously mentioned Pima cultivars with higher levels of FOV-4 resistance, there are a limited number of entries in this commercial screen that appear worth a follow-up evaluation as potential higher FOV-4 resistance varieties, including:  Group figure 1: FM 2398, ST 4550, PX 8504 Pima; Group figure 2: DGX 19014, BX 2037, FM 162; Group figure 3: Phy-60, Phy 64 through Phy 67; Group figure 4: Ark 1112-59, TAM LBB 15905, CSX 8308.

When data is compiled for the second trial location (which includes most commercial entries other than the RBTN program entries), there will also be an opportunity to determine consistency of resistance screen results for two sites.

                            Figure 2
                          Figure 1
                        Figure 3

 

 

 

 

                       Figure 4

 

 

 

 

 

 

Data Summaries for 2018

As examples of the full data sets that are provided each year as a result of this project, the following tables of this report show the summary averages for the Tipton area site (Tulare County) in 2018. Similar data will be developed and posted when 2019 results are completed.  These 2018 tables and those from prior year summaries are shown on the UC cotton web site at http://cottoninfo.ucdavis.edu . This information includes foliar Fusarium ratings, root vascular stain ratings, plant height and node number as indicators of vigor.  In coming weeks as data is processed, we will add the plant survival percentage for each entry, but it is not included in this summary.  Data shown are determined from five plants evaluated in each of three field replications per entry.  The tests include all entries in University of CA cotton variety trials, additional commercial germplasm (company selected varieties plus experimentals they submitted) plus entries from the Regional Public Breeders testing program (including check varieties, organized nationally by Dr. Ted Wallace of Mississippi).

Information to focus on in reviewing the tables as best indicators of overall responses to FOV-4 infection are: (a) root vascular stain index; and (b) survival percent at 7 weeks, since they indicate relative severity of infection and impacts on plant mortality (this data, as mentioned above, is not summarized and available at this time).

“Check” varieties that are moderately to highly susceptible include: Phy-725RF, DP-340 (moderate), while a quite tolerant check variety would be Phy-802RF.  The scale for Foliar FOV index and root vascular stain index ratings is 0 to 5, with 0 being no symptoms, 5 being severe (usually reserved for dead, near-dead plants).  Keep in mind that ratings are done at 7+ weeks post emergence, so they are done on plants surviving at the time of the rating, which in the most severely impacted  entries  can be some of the few survivor plants, with most others dead. It is recommended that the combination of lower vascular stain ratings as a relative indicator of disease severity in tested plants must be considered in combination with survival of the plants in order to assess relative levels of resistance.

 

Identification and Development of Cotton Germplasm and Potential Breeding Lines with Improved Fusarium Wilt Resistance, Fiber Quality and Yield

By
Bob Hutmacher
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0

Objectives of Research 

  1. Develop and expand the cotton progeny and breeding populations segregating for Fusarium wilt race 4 (FOV4) resistance. (efforts are roughly split between Upland/Acala types of cotton and Pima germplasm).

2. Evaluate resulting progeny, breeding lines, and germplasm for FOV resistance.

3. Utilizing selected materials, maintain seed supplies through progeny propagation and breeding population increases at field location(s) in California and in greenhouses as necessary for limited seed entries.

4. As selected germplasm are advanced, also conduct trials to evaluate growth characteristics and yield performance  (growth habit, growing season length requirements and yield performance) at West Side Research Center location

5. Identify breeding lines and germplasm with improved combinations of FOV race 4 resistance, fiber quality, and yield for release and availability to breeders and seed companies as appropriate.

 Planting tolerant/resistant varieties is an effective strategy to manage FOV4 damage and losses in cotton. Progress has been made by University of California and USDA, ARS, and the private companies from information and results generated by this and other FOV4 research projects funded through California cotton growers/producers.   Research efforts have identified and developed tolerant/resistant Pimas, as have made some progress in identifying improved FOV4 resistance in Upland cultivars.

Field evaluations have provided information for a number of generalizations: (1) most Pima cultivars show more severe symptoms and suffer higher levels of stunting and plant mortality from FOV4 than seen with most Uplands or non-Acala, and Acala cotton; (2) some moderate to highly-resistant commercial Pima cultivars have been identified from several seed companies and private breeders; and (3) several experimental Pima germplasm or breeding lines with moderate to high resistance to FOV4 have been identified, developed, and publicly released (SJ-FR01 to SJ-FR09) by the Univ. of California and USDA-ARS. These germplasm lines have helped to increase the genetic base for FOV4 resistance in Pima Cotton.

Since 2013, more than 4,000 entries and developed progeny have been evaluated in infested FOV4 fields and a portion (1/4) in the greenhouse using artificial FOV4 inoculation. Our primary objectives have been to identify/develop additional Pima cultivars, and evaluate and develop the Upland gene pool for improved FOV4 tolerant germplasm.  Efforts have included introducing a known FOV4 dominant gene that has shown resistance in Pima (e.g., Pima-S6) into Upland cultivars, as well as, introducing tolerant gene(s) from identified Upland tolerant lines from our research obtained from the USDA-ARS Cotton Germplasm Collection and University-breeding programs into elite or improved yield and fiber quality cotton lines.

For the breeding efforts, entries and progeny have been planted in naturally-infested FOV4 fields and seeded in 5-by-1 meter plots and replicated three times. During the growing season, plant responses to inoculum pressure were assessed through evaluations of root and stem vascular staining levels, plant mortality, foliar wilt symptoms and measures of relative plant vigor. Selected cotton entries used as parents to make crosses and progeny developed from these parental entries (F1 populations) were also inoculated with FOV-4 and grown under greenhouse conditions for rating. In addition, resistant/tolerant varieties or germplasm may not express similar modes of inheritance of resistance when they are derived from different genetic backgrounds or are challenged by different Fusarium types or races of different geographic origin. The postulated pathogenicity or mode of infection mechanisms and the inheritance of Fusarium resistance significantly differ among races for cotton entries or lines. Previous reports indicated FOV4 resistance is associated with a complex allelic-recombination and duplicated marker-genes between cotton chromosomes 14 and 17. Genomic islands or regions on chromosomes 3, 6, 8, 11, and 25 have also been reported to be associated with allelic dosage for FOV-4 tolerance. Additional analyses revealed that cotton lines and progeny share resistance genes for plant defense against Fusarium races (1, 4, and 7).

In Upland cotton, germplasm with improved levels of FOV-4 tolerance have been identified, and new breeding lines are being developed by USDA-ARS and the University of California with the support of the CA Cotton Alliance and the CA Cotton Growers and Ginners Association.  From 2019, more than 150 Upland breeding lines are being evaluated to validate their higher FOV-4 levels of tolerance and to identify the best FOV-4 tolerant lines for releasing to the public and private researchers and breeders. In Figure 1, the evaluation of FOV-4 results and the progress of selection of a few breeding lines from 2016 to 2018 are compared with check lines with known level of FOV-4 resistance (Shorty-Upland, Pimas: PS7 and P3-39 susceptible and PS6 resistance).

In Pima cotton, Egyptian and Peruvian Pima or long staple cotton have been evaluated for relative levels of FOV-4 resistance.  A half-dozen of these lines were selected to make crosses and develop progeny that eventually will derive new and more diverse Pima germplasm resistance to FOV4. From 2019, more than 300 Pima variants (Gossypium barbadense L.) from the country of Uzbekistan are being evaluated to identify new sources of FOV4 resistance for developing novel germplasm.

Figure 1. Average Root Vascular Wilt Staining values (VRS) of select germplasm. Examples shown are evaluations from 2016 to 2018 selections of selected entries or Parents (1-9) to be used in crosses to develop new progeny/breeding lines with improved Fusarium wilt race 4 (FOV4) tolerance (rating of vascular root staining (VRS) – scale 0 = no infection to 4 highly infected root with VRS or almost death).

Significance of Research

Fusarium wilt [Fusarium oxysporum f. sp. vasinfectum Atk. Syn & Hans (FOV)] of cotton (Gossypium spp.) in California has long been considered a serious fungal disease for cotton.  Some races of this disease were first noted in 1959 in California (Garber and Paxman, 1963), and the number of infested sites remained relatively limited until the mid-1970’s. Before 2003, FOV in California was thought to be primarily caused by race 1. Race 1 of FOV is typically found in sandy soils, with the most severe, economic impacts found when the disease organism is present in an interaction with root-knot nematodes (Bell, 1984; Veech, 1984). Susceptibility to FOV, particularly race 1 FOV is increased by the effect of the nematode’s wounds (Garber et al., 1979).  In 2003, UC Davis scientists (Kim et al., 2005) identified a race 4 isolate of FOV in California soils. Race 4 of FOV was first identified in India on Asiatic cottons and was not previously identified as a problem in the U.S. Recent field investigations (Kim et al., 2005; Ulloa et al., 2006) have found race 4 FOV in clay loam and loam soils, in which root knot nematode populations and root damage symptoms were largely absent.

The introduction of new genetic variability or genetic diversity into elite cotton germplasm is difficult and the breeding process slow. When breeders use new and exotic germplasm sources, which possess resistance disease genes, to introduce genetic variability, large blocks of undesirable genes are also introgressed during the recombination between the two parental lines (linkage drag). This linkage drag has limited the use of such germplasm. In terms of the maintenance of elite germplasm with elite genes/traits, very high constraints are placed on today’s cotton breeders. However, the competitiveness of the cotton industry will be dependent upon continuing improvements of traits such disease resistance, fiber quality, and yield.  We feel that improvements in host-plant resistance currently is the most economic and effective strategy for managing Fusarium Race 4 for continuing cotton production in the San Joaquin Valley region of California. Continuing the development of resistant cultivars or germplasm to FOV is important for reducing yield losses and reducing further expansion of the pathogen.

The primary areas of work in this project include the following:

  1. Maintain and further develop access to one (preferably two) field test sites infested with race 4 FOV as well as greenhouse space to continue resistant germplasm testing in the San Joaquin Valley.
  2. Using field and greenhouse screening sites available to us, test cotton progeny and breeding lines and continue making crosses with potential for improved FOV-4 resistance. Collect seed from self and open pollinated cultivars of interest/improved FOV-4 resistance or other traits, delint and prepare seed for plantings for further FOV-4 testing of segregating populations and for seed increases necessary to allow further agronomic testing for yield and quality, plus to provide seed for interested breeders for further development.
  3. A link to ongoing plant genetics program in FOV resistance of Dr. Ulloa and his continuing molecular work is a vital part of this project plan. Identification of developed breeding lines and germplasm with improved FOV resistance through molecular breeding increases the need for molecular markers because molecular markers facilitate selection of resistant cottons, and decrease cost, time, and the risk associated with subjective greenhouse or field phenotypic evaluations. Molecular markers can also help in the identification of the genes that provide host-plant resistance against FOV.
  4. Under current arrangements with USDA-ARS cooperators, one additional major part of the project is to produce, maintain and expand seed supplies for advancing germplasm. Work to be done includes seed preparation, progeny propagation and breeding population increases at field and greenhouse location(s) in California.

Progress on Objectives

  • A series of 4 to 9 Pima lines were grown for seed increase with intention of release as improved “SJ” series lines from program efforts since 2014. These lines are meant to have superior FOV resistance with the capacity to be used as germplasm in breeding programs.  Bolls of each line were harvested and have been evaluated for fiber quality parameters.
  • An additional 50+ lines were selected from other populations the past two years, as well as an additional dozen or more selections made from those with superior FOV resistance and fiber quality.
  • During the 2017 and 2018 seasons, more than 160 additional Upland entries/germplasm were evaluated under a FOV race 4 infested field in California. These entries represent a wide range and diverse genetic backgrounds of germplasm material or cotton types. We continue to follow our established breeding scheme or strategy for identifying, selecting, and developing FOV race 4 resistant/tolerant germplasm. Selected breeding lines from 2013-2014 and now re-selected in 2015 through 2018 have been examined and targeted for the introgression of FOV race 4 resistance/tolerance genes from entries such as Pima-S6 (PS-6), Upland TM-1, and Acala FBCX2, an original pedigree-parental line of Acala NemX. So far from this set of derived progeny, around 20 breeding lines continue to show FOV race 4 resistance-improvement, and about 12 to 15 lines were re-selected in a seriously infested field this and last season. In addition, we continue to search for new sources of FOV race 4 resistance/tolerance within the Upland germplasm gene-pool by evaluation of around 150 added entries in each of the past several years.
  • In 2018, 2017 and 2016, as in prior years, over 100 newly tested genetic-diverse Upland and some Pima entries/germplasm were evaluated for FOV race 4 tolerance. These entries were also received from screening and selection efforts at the USDA-ARS, PSGD Laboratory, Lubbock, TX. From this set of entries, about two dozen additional cultivars were identified with good levels of FOV race 4 tolerance. Selected entries were self-pollinated for seed increase and further testing, and entries were evaluated in fields for FOV resistance and other desirable plant characteristics in field trial sites in 2018.  Similar efforts are underway from 2019.

Evaluation of Inoculation and Screening Strategies in the Greenhouse and Field

Grain carriers (wheat, rye ) were inoculated with FOV race 4 and added to the soil in whole grain and ground form to the soil at both of our field FOV-4 screening sites (Tulare County and Kern County) to supplement existing FOV-4 inoculum and assess the feasibility of using with these substrates as potential methods of inoculation compared to the current standard of liquid conidial inoculation used in our greenhouse inoculation and screening trials.  We utilized rye grain in 2017 and 2018 field  trials due to what appeared to be superior inoculum development compared with other tested grains.

Dr. Maggie Ellis of CA State University Fresno has worked on some seed inoculation in growth chamber settings, with FOV-4 seedling evaluations done at intervals after pathogen exposure.  The approach could be helpful as an alternative quick-screening method alternative to the root dip method we have been using in the UC Kearney REC greenhouse.  We have worked with her graduate student (Josue Diaz) and Dr. Ellis in field assessments and greenhouse assessments, and feel that there will be value in combining some of these early screening approaches with field assessments for more complete cultivar disease resistance evaluations. With that in mind, there is evidence to suggest that  rolled towel methods may be useful as a reliable pre-screening test to identify materials that are so susceptible that field screens are unnecessary; and additional work is needed to identify a reliable severe test that could be replicated as a follow-up/critical test to further verify the best-performing cultivars/germplasm identified in field screening tests (both could be very useful in breeding programs.)

Developing a Broad Germplasm Base of Populations for Future Selection of Material With Advanced FOV Resistance and Good Fiber Quality

As materials are developed for which we require seed production as well as more advanced agronomic testing for yield or fiber quality, fields have been set up at UC West Side REC for seed increase needs, and screen materials developed for larger scale self pollination needs. As needed, we will develop new crosses for promising materials, and continue to utilize lines developed based on crosses made in the past few years in order to provide not only resistant Pima materials but also develop some Upland / Acala FOV-4 resistant/tolerant materials.

In all evaluations of responses of cultivars to FOV race 4 pressure, rating procedures are standardized across sites and experiments.  Measured responses to FOV will include percent plant survival and standardized ratings of disease severity and vascular discoloration.  Vascular discoloration of the lower stem and upper tap root are observed by slicing the stem longitudinally, and rated according to the scale of 0) no symptoms, 1) light staining as spotty areas, 2) light colored staining, continuous and covering ¼–½ of the stem diameter, 3) moderate brown or black staining in a band encircling most of stem cross section, 4) brown or black staining  across most vascular tissue in cross section, and 5) dark brown or black staining accompanied by plant death.

A very large-scale effort for seed production was made in 2018 on about 1 acre of tented or bagged plants (to prevent bee pollination), with a much smaller (about 1/4 acre) similar tented planting for seed increases done also at West Side REC in 2019.   The photos shown below were taken in August, 2018, and show an approximately two acre area with about 1 acre of planted rows (split into two fields) where we grew out some selections and crosses that we determined to have improved FOV-4 resistance (as determined in multiple field disease resistance screenings).  For 2018, there were about 600 bagged or “tented” plots in these two fields at the UC West Side REC, representing close to 400 different entries for which we grew out plants to be self-pollinated to increase seed amounts for continuing work, and in many cases, to provide seed for additional testing and release to breeders.   The purpose of the” bee-proof” netting used in the tenting and bags is to prevent insects from cross pollinating the cotton that we want to be self-pollinated for seed increase/production.

“Bee-proof” netting used in the tenting and bags helps prevent insects from cross pollinating the cotton that researchers want to be self-pollinated for seed increase/production. (Photo courtesy of B.Hutmacher)

As examples of the work being done on several fronts (Pima, Upland, crosses), in field trials done in heavily FOV4 infested fields, we evaluated lines, crosses and some reselections based on current and prior year screening efforts, with the following examples of some cultivars being advanced in the testing program:

  • Egyptian source Pima entries: Three entries selected for advancement based on very good FOV vascular stain ratings.
  • Crosses made in 2015 and 2016 (Pima x Upland crosses): 31 entries advanced in selection for seed increase based on very good FOV vascular stain ratings.
  • New Entries from Upland Program and Collection of Mauricio Ulloa for 2017: 17 entries advanced in selection for seed increase based on good to very good FOV stain ratings.
  • Experiment #9 (based on 2015 and 2016 Pima selections tested for FOV-4 tolerance at Tulare County site): 10 entries advances in selection for seed increase and further testing based on good FOV stain ratings and agronomic characteristics – tested multiple years and sites.
  • Experiment #10 (based on 2015 Upland selections tested for FOV-4 tolerance at Tulare County site): 5 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.
  • Experiment # 11 (F-2’s based on 2014 Crosses at Tulare Co. site (some Upland and Upland-by-Pima included) followed by reselections in Greenhouse evaluations: 22 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.
  • Experiment #12 (both Upland and Upland by Pima crosses at Tulare County site): 17 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.

Verticillium Wilt Resistance of Newer Germplasm in Pima, Acala and California Upland Varieties

By
Bob Hutmacher
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0

The overall objective of this research is to evaluate field screening location(s) with a moderate to high level of sustained Verticillium wilt inoculum to provide location(s) for field screening of cotton germplasm of interest in CA Cotton production.  The aim of the work will be: (1) to sustain a relatively small location (approximately 0.5-1 acres) at the West Side REC where we can maintain a Verticillium wilt population for field screenings to identify relative susceptibility of newer commercial varieties of interest for California cotton production, and for screening of experimentals from both commercial breeders or seed companies and those from USDA-ARS or other public breeding programs; and (2) to support evaluation of relative Verticillium wilt levels in cultivars being tested in the FOV race 4 screening location(s).

Some of the evaluations have either not been done (West Side REC) for 2019 or have not yet been summarized (Tulare County site) at the time of preparation of this report since the best time for evaluations of this type are generally mid- to late-summer. Results from the 2019 field evaluations will be summarized when data is available.

Summary from 2018

Tulare County Location:

All entries grown in the FOV race 4 screening trials were grown at a location with Verticillium present, which also turned out to be a location that had race 4 FOV present.   The screening for Verticillium was still done at this location since the plantings were in place and we considered it to be useful information, and the Verticillium screening was done on a minimum of 5 plants per entry per replication, for a total of 15 plants per entry to rate for incidence (of plants with Verticillium evidence in the stem – vascular staining about 1/4 to 1/3 of the way up the stem, as compared to root vascular staining evaluations for FOV).

West Side REC location:

Evaluations were done at a site at the West Side REC of the University of CA where we planted small plots for evaluation. The screening for Verticillium was done at this location on 7 plants per entry per replication, for a total of 21 plants per entry to rate for incidence (number of plants with Verticillium evidence in the stem – vascular staining about 1/4  of the way up the stem, as compared to root vascular staining evaluations for FOV).

The overall objective of this research is to evaluate field screening location(s) with a moderate to high level of sustained Verticillium wilt inoculum to provide a location for field screening of cotton germplasm of interest in CA Cotton production.  The aim of the work will be: (1) to sustain a relatively small location (approximately 1 acre in multiple variety trials) at the West Side REC where we can maintain a Verticillium wilt population for field screenings to identify relative susceptibility of newer commercial varieties of interest for CA Cotton production, and for screening of experimentals from both commercial breeders or seed companies and those from USDA-ARS or other public breeding programs; and (2) to support evaluation of relative Verticillium wilt levels in cultivars being tested in the FOV race 4 screening locations.

The intent of continuing this work on a relatively small scale, and with data reported from both West Side REC and field trial locations where we also are doing Fusarium race 4 field screening is to develop information on Verticillium wilt incidence in currently-grown and possible future cultivars of interest for California cotton production.  Verticillium wilt incidence was evaluated in 5 plants per field replication at each field site.  The intent is that UC and USDA-ARS investigators as well as seed company representatives and breeders could use this information in determining the relative need for follow-up evaluations and screening efforts for Verticillium wilt susceptibility as they advance cultivars through their selection processes. The charts attached to this brief report give an indication of the levels of Verticillium seen during the current year evaluations for the broad mix of cultivars.

Verticillium wilt incidence evaluations were done on a large collection of experimental Pimas and Uplands that were included in our Uplands Advanced Strains trial, plus experimentals submitted by seed company representatives or breeders, plus public breeder entries in the RBTN (Regional Breeder Testing Network) evaluations coordinated by Ted Wallace of Mississippi State University in cooperation with the USDA-ARS.  Figures 1 through 5 show Verticillium incidence in commercial Upland/Acala & advanced experimental Uplands at Tulare County site in 2018 field evaluations.   The five graphs show data for over 100 entries plus three check varieties.  The check varieties were evaluated for consistency of data across field replications, and generally incidence of verticillium was evident across all three field replications in most entries.   Check varieties included were:  DP-340 Pima, Phy-888RF Pima and Mon-109-C7 Experimental Pima.

Data for the Tulare County site and the West Side REC site for 2018, and similar
results will be prepared when 2019 data is available on the UC Cotton Website.
Verticillium incidence is generally higher in Upland varieties than in Pima varieties. However, there are examples of very low incidence, or even zero incidence cultivars in both Upland and Pima data particularly at the Univ CA West Side REC site, but in some cases
also at this one Tulare County site. It was interesting that the experimental
Egyptian Pima cultivars worked with in recent years and in crosses did not
appear to be susceptible to Verticillium, at least at 2018 evaluation sites. Similar
data will be collected from two sites in 2019 and made available after analysis.

The intent of this work is to provide it to seed companies as a means of identifying materials that may require some additional evaluations for Verticillium susceptibility as they move forward in their breeding programs.

Pima On-Farm Variety Trials, Pima Research Center Variety Trials

By
Bob Hutmacher
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0

Project Summary

Field evaluations of Pima cotton varieties will be conducted at a UCCE Research Center location (West Side Research and Extension Center) and at 3 grower field sites as follows:

  1. For 2019, we conducted trials at the UC West Side REC and 3 grower field farm sites. Sites are located in Kings County, Kern County, and Merced County); and
  2. For 2018, we conducted Pima variety trials at the West Side REC, Fresno, Merced and Kings County grower sites; and
  3. We offered the opportunity to conduct smaller-scale research plot variety trials of Pima varieties at the West Side REC, including any experimental varieties supplied by seed companies where seed quantity available for testing is limited.

Preliminary Summary of 2019 Year

2019 Trial Activities:

Entries included in the field trials for 2019 included the following cultivars planted at West Side REC and Farm locations. Results of trials each year will be available at the same UC cotton web site mentioned for prior year results.

Entries Planted in 2019 Pima Variety Trials – West Side REC: DP 341 RF, DP 348 RF, Phy PX 8504RF, DP 359 RF, PHY 841 RF, PHY 881 RF, PHY 888 RF, HA 1432, PHY 802 RF, and PHY 805 RF.

HA 1432 was also planted at a Merced Co site.  Phy-802 RF and Phy-805RF were only at WSREC.

Entries planted at the grower sites will be reported by individual sites.  There were differences in the entry list due to expressed grower interest and willingness to have plantings, and some differences due to limited seed availability.   Complete list of plot maps at each site can be available on request.  For the most part, the varieties planted were the same as at WSREC, except for some sites that did not want the Hazera hybrid, which is non-transgenic and not glyphosate herbicide resistant.

Research Center and Farm Trial Sites: West Side REC, Kern County – Bone Farms, Merced County – Bowles Farms, Kings County – Hansen Ranches. In addition, all of the entries in these trials were included in our field Fusarium race 4 screening trials for 2019 as in all prior years. A selection of Pima varieties from Egyptian sources were planted at a Merced County site for evaluations in including yield potential, earliness and FOV-4 resistance, and if possible, fiber quality samples will be collected for hvi evaluations.

Results from those trials will be summarized and reported in our final screening information after completion of field data and analyses.  The results will be available on the University of CA cotton web site at http://cottoninfo.ucdavis.edu

The 2019 field trials were still underway at the time of this report, so there are no yield results or other hvi results from 2019 trials available.  The 2018 results from Pima variety trials are available on the web site mentioned.

Upland and Acala Research Center Variety Trials

By
Bob Hutmacher
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0

Acala and Upland acreage continues to be far less than Pima plantings in this and recent years. There are tradeoffs in shifting to Pima (typically reductions in yields) and in shifts to non-Acala Uplands (typically lower price for lint), and growers need reliable, unbiased information regarding expected lint yields and fiber quality in order to make reasonable, lower-risk decisions.   All of the entries in both types of trials were harvested in late October or in November by spindle picker (center two rows harvested out of four row wide plots). Subsamples from all field replications of the trials at both sites will be collected, and will be ginned starting in early December on a mini-gin, since the Shafter Research gin is no longer in operation due to budget restrictions. Subsamples from all plots will also be submitted for hvi analyses run through the USDA Classing office in Visalia, Calif.

2019 Trial Activities:

Entries included in the field trials included the following planted at West Side REC locations (CA Upland Advanced Strains trials) and at Shafter and West Side locations (UC Acala/Upland variety trials). Results of trials will be available at UC cotton web site mentioned for prior year results.

Entries planted in 2019 UC / Cotton Inc. / CCGGA Research Funded Acala / Upland Variety Trials – West Side REC location only for 2019: FM 1830GLT, ST 4550GLTP, FM 2398GLTP, ST 5600B2XF, ST 5707B2XF, FM 2498GLT, ST 5471GLTP, FM 2574 GLT, PHY 764WRF, DP 1646B2XF, DP 1820 B3XF, and DP 1845B3XF.

Entries Planted in 2019 CA Upland Advanced Strains Variety Evaluations – West Side location: Phy-764 WRF (check), DGX 19001 B3XF , DGX 19014 B3XF, DGX H929 B3XF, BX 2002 GL, BX 2005 GLT, BX 2037 GLT, BX 2016 GLTP, BX 2022 GLTP, BX 2076 GLTP, BX 2398 GLTP, FM 2498 GLT, ST 5600 B2XF, ST 5707 B2XF, FM 1621 GL, 18 R411 B3XF, 18 R421 B3XF, 18 R423 B3XF, 18 R438 B3XF, 18 R445 B3XF, 18 R448, and B3XF.

Entries Planted in 2019 Western and National Entries–NATIONAL STANDARDS TRIALS  – West Side REC location: DP 1646 B2XF, NG 4545 B2XF, PHY 764 WRF, PHY 499 WRF, DAYTONA RF, DP 1549 B2XF , FM 1830 GLT , FM 2574, and DP 1522 B2XF.

Entries Planted in 2019 RBTN (Regional Breeder Testing Network) Program–West Side REC location LA16063019, LA16063033, LA16063054, 13AFX6-27-2, 13AFX13-12-5, Ark 1115-36, Ark 1102-55, Ark 1114-21, Ark 1117-60, Ark 1124-50, Ark 1112-59, TAM 13S-03, TAM 12J-39, TAMLBB15905, TAMLBB16507, GA2016024, GA 2016099, GA 2016103, MS 2010-87-37, CSX 8308, DP 393 check, DP 493 check, FM 958 Check, UA 222 check.

All of the entries in these trials were included in our field Fusarium race 4 screening trials for 2019 at one location. Results from those trials were summarized and reported in our final screening information, with results on the University of CA cotton web site at http://cottoninfo.ucdavis.edu.  The type of information provided in these field trials on variety performance in the CA Uplands Advanced Strains Trial and Acala/Upland West Side REC and Shafter (for primary Upland/Acala trial) for 2019 focused mostly on yield performance, gin turnout, and fiber quality components.   This information will be available following the conclusion of the growing season, and data presentation will be via the UC cotton website, or paper copies can be provided on request. In addition to the yield data we also make available the summary fiber quality / hvi testing data from the samples submitted to the Visalia USDA classing office.

2018 Project Summary
The overall project supports in part conducting three types of variety trials:

a. Testing of commercial non-Acala Upland varieties (and remaining Acala types if      available), with a target of two sites (one on-farm site or Shafter Research Station site in Kern County if possible, plus the University of CA West Side REC for these trials); and

b. Small scale testing at the UC West Side REC of a range of Upland varieties that are either only available in small seed quantities or that are experimental or of limited current commercial interest for grower field trials (CA Upland Advanced Strains Trials)

c. Small scale testing at the UC West Side REC of entries in the National Standards and Western Regional trials in a small plot, four replication trial at this one site.

For 2018, the set of trials planted were:

d. Acala and non-Acala Upland varieties to bed grown in two sites including a plot trial at the University of CA West Side REC in Fresno County and the former UC/USDA field station site in Shafter, CA in Kern County; plus

e. A small plot trial with limited seed availability CA Upland cultivars (or entries of limited or unknown commercial interest for the San Joaquin Valley), with the plots established at the West Side Research and Extension Center.

f. Entries in the UPLAND COTTON Western Regional and National Standards trial coordinated by USDA-ARS, with entries supplied for western region by Alison Thompson, USDA-ARS, Maricopa, AZ on request of the national standards committee

This project, with partial support from Cotton Incorporated plus added support from the CA Cotton Ginners and Growers Association Research Fund and from participating seed companies for the Advanced Strains trial, is now the only public variety testing program for Upland/Acala varieties of potential interest for San Joaquin Valley cotton production.

The small plot trials have 4 replications, with plots 4 rows in width by 60 to 70 feet in length (depending upon seed availability and locations used for the trials).  The test sites at the West Side Research and Extension Center in Fresno County were planted the third week of April this year, and the Shafter site was planted in the third week of April this year.  The goals of the project are to provide trial sites for testing a large number of entries of potential interest to seed companies and growers, with entries chosen to assess relative performance in SJ Valley settings and areas where Uplands/Acalas have been of at least some continuing commercial interest.

Data Collection and Availability From Field Trials:

Summaries of prior year trial results are available at http://cottoninfo.ucdavis.edu). In addition, results are presented at the Cotton Workgroup meetings and at winter and spring grower/PCA meetings of the University of California.  Results of the trials will be reported in winter meetings of the UCCE Specialist and Farm Advisors, and will be available in a printable form (pdf or Word) as full tables on the University of California cotton web site: http://cottoninfo.ucdavis.edu

Field Work for 2018

Acala and Upland acreage continues to be far less than Pima plantings in this and recent years.  There are tradeoffs in shifting to Pima (typically reductions in yields) and in shifts to non-Acala Uplands (typically lower price for lint), and growers need reliable, unbiased information regarding expected lint yields and fiber quality in order to make reasonable, lower-risk decisions.

All of the entries in both types of trials were harvested in late October by spindle picker (center two rows harvested out of four row wide plots).  Subsamples from all field replications of the trials at both sites were collected, and will be ginned starting in November on a mini-gin, since the Shafter Research gin is no longer in operation due to budget restrictions.  Subsamples from all plots will also be submitted for hvi analyses run through the USDA Classing office in Visalia, CA.

*If the services are available, we may try to run two replication subsamples per variety through the Shafter Research Gin, if it is in operation this year, in order to provide more reasonable gin turnout estimates.

2018 Trial Activities:

Entries included in the field trials include the following planted at West Side REC locations (CA Upland Advanced Strains trials) and at Shafter and West Side locations (UC Acala/Upland variety trials). Results of trials will be available at the UC cotton web site mentioned for prior year results.

  • All of the field plots at the West Side REC yielded and looked relatively good, despite heavy early- to mid-season lygus pressure and the hottest July on record in the Fresno County and San Joaquin Valley area (with over 30 consecutive days with high temperatures in excess of 100 degrees F).  Some of the bottom crop was lost due to lygus pressure, with some losses also attributable to high nighttime temperatures
  • As with the past two years, we no longer have access to the Shafter Research Gin at the old Shafter Research Center, so the only gin turnout and lint percent data available are those derived using mini-gins, with no other cleaners other than hand removal of trash materials during the ginning process.

All of the entries in these trials were also included in our field Fusarium race 4 screening trials for 2018 at one location.  Results from those trials were summarized and reported in our final screening information, with results on the University of CA cotton web site at http://cottoninfo.ucdavis.edu

The type of information provided in these field trials on variety performance in the CA Uplands Advanced Strains Trial and Acala/Upland West Side REC and on-farm trials focuses mostly on yield performance, gin turnout, and fiber quality components.   This information is available via the UC cotton website mentioned earlier, or paper copies can be provided on request. In addition to the yield data we also make available the summary fiber quality / hvi testing data from the samples submitted to the Visalia USDA classing office. Thank you for the past and current support of these trials.  If you have questions, please direct them to Bob Hutmacher at (559) 260-8957 or rbhutmacher@ucdavis.edu.

Overview of Ongoing Research on Cotton in California

By
PCC
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0

Despite reduced acreage in recent years, research in California cotton is alive and well.  In fact, with the establishment of a coordinated research meeting held every September, research in California cotton is as strong and harmonized as it has ever been.  Growers, Gin Managers and industry leaders come together in September to review research proposals on California cotton and make sure that funds are spent wisely and effectively in a coordinated manner.  This ensures what limited resources the industry does have are stretched to the maximum extent possible to keep California cotton in the forefront.

Research dollars are focused on addressing California cotton’s most pressing needs as identified by the industry at this time.

They are in order of ranking:

  1. Diseases (FOV resistance, variety screening, seed and soil treatments, pathology work in lab and field plus Seedling Disease issues)
  2. Sticky Cotton (Development of better detection and measurement system and standards and continue educational efforts)
  3. Contamination (Research ways to detect plastic in the seed cotton and eliminate where possible)
  4. Insect Management and Control (Efficacy screening of new and old products and promote intro of new chemistries with low VOC, focus on Lygus and Aphid control)
  5. Water Management (Regional with varying soil types and irrigation methods with emphasis on efficiencies, conservation, nitrogen, and salt management)
  6. Weed Management (Resistance Management to existing products and introduction of new chemistries)
  7. Nutrient Management (Focus on nutrient management while taking into account factors of soil type, irrigation method, efficiencies, etc.)type, irrigation method, efficiencies, etc.)

Funds from Cotton Incorporated (CI), the California Cotton Alliance (CCA), and the California Cotton Ginners and Growers Association (CCGGA) are coordinated and used to fund this critical research.  Funds from CCGGA come through an assessment on cotton planting seed by the California Crop Improvement Association (CCIA).

The following are papers on the most recent research as compiled by CCGGA.  Please take this opportunity to thoroughly review this document and come to understand how growers’ money is being spent to preserve the California cotton industry and help address its biggest challenges.

 

Kasugamycin for Managing Walnut Blight

By
J. E. Adaskaveg and L. Wade
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Figure 1. Pistillate flowers developing into healthy walnut fruitlets (left) and showing a primary infection (center) at the blossom end. Developing walnuts (right) with primary (blossom end) and secondary (fruitside) infections. All Photos Courtesy of Jim Adaskaveg.

How does kasugamycin-copper or -mancozeb mixtures compare to copper-mancozeb?

Kasugamycin (tradename Kasumin) was registered in 2018 for managing walnut blight and bacterial canker and blast on sweet cherry. The bactericide was already federally registered for fire blight on pome fruit, but in 2018, registration for this disease was also approved in California. Kasugamycin is a unique bactericide because it is not used in animal or human medicine. Environmental monitoring studies have shown that it does not select for human bacterial pathogen resistance with uses in plant agriculture. Furthermore, kasugamycin has its own Fungicide Resistance Action Committee (FRAC) Code 24 or mode of action that is different from other registered plant agricultural bactericides like streptomycin (FRAC Code 25) and oxytetracycline (FRAC Code 41). Kasugamycin meets new toxicology standards for pollinating insects (e.g., honey bees), it has a low animal toxicity with a “Caution” rating and a 12 h re-entry time on the label. As with any cautionary pesticide, mixers and applicators need to have standard personal protective equipment (PPE) when handling the bactericide.

Copper is classified as FRAC Code M1 for the first element historically used for fungal and bacterial disease control. Copper affects many physiological pathways in plant pathogens and is classified as having a multi-site (M) mode of action. Not many bactericides have been developed for managing plant bacterial diseases, and fewer have been registered. Thus, there has been a great dependency on copper. Because of the multi-site classification, many agriculturalists thought that plant pathogens would not develop resistance to copper. Unfortunately, after many years of usage, bacterial pathogens such as the walnut blight pathogen, Xanthomonas arboricola pv. juglandis (Xaj), have developed resistance to copper. This is a direct result of overuse of one active ingredient (i.e., copper) and being limited with the lack of bactericides available to apply modern approaches to resistance management such as rotating between active ingredients with different modes of action and limiting the total number of applications of any one mode of action per season as part of following “RULES” (http://ipm.ucanr.edu/PDF/PMG/fungicideefficacytiming.pdf). Over-usage of any one active ingredient, such as copper, can create other environmental issues including soil contamination, orchard water-runoff, higher concentrations in watersheds, and potential crop and non-crop phytotoxicity especially in perennial crop systems.

After the industry used copper exclusively for approximately 50 years (1930s to 1980s), copper-maneb (e.g., Manex) mixtures were first identified for use on walnut in 1992 and emergency registrations ensued for 22 years before a full registration was obtained for the related compound mancozeb in 2014. The walnut industry and University of California (UC) researchers knew that more alternatives were needed, otherwise someday the pathogen would develop resistance to copper-mancozeb. Because copper resistance had already developed, this selection pressure is maintained and resistance levels are increasing even when mancozeb is used in the mixture, because copper has been the only tank mix option. In effect, resistance management is not being effectively practiced since copper-resistance already exists and the use of mancozeb (M3) is selecting for resistant strains of the bacterial pathogen to the mancozeb mode of action. Having only one treatment (i.e., mancozeb) available to manage a disease not only can limit crop production each season but could economically devastate the entire industry by making harvests sporadic and inconsistent, lowering crop quality, and preventing profitability. Growers and the entire walnut industry consider walnut blight a threat to the industry and their livelihood.

Why do we need kasugamycin for managing walnut blight?

There is a great need to develop other modes of action for managing bacterial diseases including walnut blight that can be integrated into management programs. Kasugamycin was identified, developed, and registered for the purpose of resistance management, reducing over-usage of any one mode of action, and sustaining the walnut industry of California. The aminoglycoside bactericide has a unique mode of action (FRAC Code 24) as stated above and can be used in combination with copper or mancozeb. When kasugamycin is used in combination with mancozeb, resistance management is being practiced since resistance has not been found in Xaj pathogen populations to either mode of action.

Use on Walnuts

Kasugamycin is labeled as Kasumin for managing walnut blight at 64 fl oz/A in a minimum of 100 gal water/A for ground application. The full 64 fl oz per acre labeled rate for kasugamycin should always be used. Adjuvants that are stickers may also be used, whereas spreaders and penetrants should be avoided. Reduced spray volumes may be utilized for small trees provided that the volume of water is sufficient to provide good coverage of treated foliage. Applications should be initiated when conditions favor disease development. This is the same timing as for copper-mancozeb. In orchards with a history of the disease and when high rainfall is forecasted, applications should be initiated at 20-40 percent catkin expansion. Under less favorable conditions for disease (i.e., low rainfall forecasts and minimal dews), applications should start at 20-40 percent pistillate flower expansion (also known as the “prayer stage”). The preharvest interval is 100 days or approximately mid- to late June depending on the walnut cultivar harvest date. The minimal re-application interval is seven days. The current labeled uses of Kasumin allows for two applications or 128 fl oz of product per season with a label change for up to four (256 fl oz) per season planned later this year. Still, only two consecutive applications will be allowed without rotating to other modes of action. Alternate row applications, applications in orchards that are being fertilized with animal waste/manure, or animal grazing in orchards treated with Kasumin are not allowed. The first restriction is to prevent selection of resistant isolates of the target pathogen, Xaj; whereas, the latter two restrictions are to ensure that the selection of non-target, human-pathogen bacteria is prevented.

For walnut blight management, the best way to use the bactericide is in combination with mancozeb or copper. Application management strategies for a four- or five-spray mixture, rotation program include, but are not limited to, the following:

A) Copper/mancozeb—kasugamycin/mancozeb—kasugamycin/copper—copper/mancozeb

B)  Copper/mancozeb—kasugamycin/mancozeb—copper/mancozeb—kasugamycin/copper — copper/mancozeb

How do kasugamycin treatments compare to copper-mancozeb treatments in managing disease?

The research used to develop kasugamycin was based on a 7- to 10-day re-application interval. The reason for this was that Kasumin is locally systemic or translaminar and thus, is less likely to be re-distributed. With new growth increasing the canopy volume weekly in the spring as walnut trees come out of dormancy, multiple and frequent applications are necessary. Kasugamycin-mancozeb mixtures applied in our research trials were often the most effective of all treatments evaluated.

Radial streaks of 16 isolates of Xaj on each plate exposed to different toxicants. Top image: Copper 50 ppm (fixed concentration). Spiral gradient plates with the highest concentration towards the center and lowest concentration at the edge of the plate. Middle image: Kasugamycin (gradient range 0.5 to 64.9 ppm); and Bottom image: Kasugamycin + mancozeb (concentration gradients). Lack of growth towards the center of each plate indicates inhibition. No inhibition for copper at 50 ppm whereas inhibition concentrations averaged 20 and 5 ppm for kasugamycin and the kasugamycin – mancozeb mixture, respectively.

In general, bactericides have a short residual life of a few days to a week or two. In toxicology in-vitro testing, Xaj is only moderately sensitive to kasugamycin with a mid-range to high minimum inhibitory concentration (MIC) value. When kasugamycin is mixed with mancozeb, the MIC of the mixture is approximately 5 parts per million (ppm). Kasugamycin is applied at 64 fl oz per 100 gal or 100 ppm. Thus, the labeled rate of kasugamycin-mancozeb mixtures are approximately 20X of the MIC value for Xaj. Because of the short residual activity and a moderate buffering residue (20X), the rotation of bactericide mixtures containing kasugamycin described above need to be applied in 7- to 10-day intervals.

Kasugamycin and Resistance.

Resistance is a relative term indicating a change in sensitivity to an inhibitory compound. A moderately high MIC for a bactericide does not mean that the pathogen is resistant. We have conducted baseline studies with kasugamycin, kasugamycin-copper, and kasugamycin-mancozeb for Xaj with MIC values of 20, 8.3, 5.3 ppm, respectively. This was done before the bactericide was registered in California to determine any change in sensitivity after registration and commercial usage. To date, resistance has not been found and isolates evaluated are all within the baseline distributions.  Still, with a single site mode of action compound such as kasugamycin, there is a risk for selecting resistant sub-populations of the pathogen especially when resistance management strategies are not employed. This is the reason why we developed the mixture-rotation programs suggested above.

Efficacy of treatments for managing walnut blight. Treatments applied using an air blast sprayer (100 gal/A). The walnut blight pathogen was sensitive to copper. Disease incidence is the number of diseased nuts per 100 nuts evaluated. Four single – tree replications were used for each treatment. Bars followed by the same letter are not significantly different.

Conclusions

The integration of bactericides with different modes of action and application strategies of rotations of mixtures of bactericides with different modes of action with forecasting tools such as XanthoCast (http://www.agtelemetry.com/) should provide the stewardship necessary for having the tools available for managing walnut blight for years to come. The hope with the Kasumin registration is to provide resistance management and prevent or reduce the risk of resistance to copper-mancozeb while new approaches can be developed and integrated to protect both of these compounds. Walnut blight is the most serious disease impacting growers in California and multiple tools like kasugamycin, copper, and mancozeb need to be available to maintain a successful industry.

Biostimulants and Grape Production

By
PCC
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0

Biostimulants are a broad category of biological products used in crop production to enhance and/or improve conventional nutrition programs. The term “biostimulant” was officially defined in the Agricultural Improvement Act (aka Farm Bill) of 2018 as:
“[Plant biostimulants are] a substance or micro-organism that, when applied to seeds, plants, or the rhizosphere, stimulates natural processes to enhance or benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, or crop quality and yield.”

However, on March 25, 2019, the US Environmental Protection Agency (EPA) released a report titled, “Draft Guidance for Plant Regulator Label Claims, Including Plant Biostimulants” to better understand manufacture label claims for plant growth regulators and biostimulants. In it, the EPA defined biostimulants in much the same way as found in the Farm Bill, except that EPA’s definition refers to improving soil as a possible outcome rather than crop quality or yield.

The EPA is deciding if and how biostimulants should be regulated. If manufacturers make claims that are similar to plant growth regulators, which are subject to regulations found in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), then they would require registration with the EPA. Some see this as an opportunity to raise the bar on biostimulant products, and reduce outrageous claims not supported by replicated field research. Others are less optimistic about more regulation and the potential for increased costs on useful products or the complete loss of product categories.

Biostimulant Categories

Biostimulants fall into three general categories 1) acids (such as fulvic or humic), 2) microbials (such as beneficial fungi or rhizobium), and 3) extracts or secondary metabolites (such as polyphenols or botanicals). However, there are other types of products, such as nitrogenous compounds or proteins, which don’t fit neatly into the primary categories (Heacox 2018). Acid based products can be applied as foliars, through irrigation systems, or directly to the soil. Depending on application, they have been shown to reduce plant stress, increase root growth and/or improve soil health. Microbial products are primarily fungi or bacteria that help improve nutrient uptake either directly or by improving soil conditions for the plant. Some microbial products may need an incubation period prior to use, which requires planning if large acres will be covered. Extracts can also be applied as foliars or through irrigation systems. They have been found to improve soil conditions for roots or microbes that are able to make elements more available.

Biostimulants vs Fertilizers

It is important to remember that biostimulants are not fertilizers. Inorganic fertilizers are mineral salts that consist of single or multi-nutrient constituents in varying ratios (i.e. calcium ammonium nitrate=CAN17). In contrast, organic fertilizers are plant and/or animal derived products that also have varying ratios of elements. Both types of fertilizers are regulated with a focus on quality and quantity guaranteed by manufactures. Biostimulants are biological products that improve crop growth through a variety of methods (i.e. reduce plant stress, improve nutrient uptake). They may have some low levels of nutrient value, but that is not their primary benefit to crops. Biostimulant activity is not fully understood but it is thought that they act indirectly to improve crop health by increasing soil microbe activity, or through the additions of acids, plant hormones, or metabolites that react with the biological processes.
Biostimulant research is ongoing and has increased substantially since 2010 to help demonstrate their impact and activity on plant growth. Dr. Russell Sharp of Plater Bio, who spoke with AgriBusiness Global, said that in 2010 a combination of new technologies, increasing interest from investors, and lower growth in traditional pesticide and fertilizer sales, led to a greater interest in biostimulants (Pucci 2018). Given the number and diversity of biostimulants, performance claims about what can be achieved when applied to a crop vary widely. Some evidence suggests biostimulants may reduce plant stress by improving soil environmental conditions when there is a water deficit, high disease pressure, non-optimal pH, or salinity levels in the soil that might otherwise reduce plant health or growth. Under these conditions, biostimulants are thought to increase nutrient uptake and yield, and may even improve fruit quality. Some research has found microbial products solubilize essential nutrients to increase their availability to the crop and enhance drought tolerance by stimulating root growth (Calvo et al. 2014). Still, while some work has shown that adding microbes to the soil benefits crops, other research shows less positive results. One study found establishment of arbuscular mycorrhizal fungal inoculants was highly variable at best and did not significantly improve crop growth even when they were present (Hilton 2019). Limited conclusive data suggests growers should view biostimulants as products that enhance the efficiency of fertilizers so that less is required during the season.

Considerable research has focused on biostimulant use in annual crops, but less research exists for permanent crops such as grapes. Biostimulant grape research has mostly been with foliar applications. Foliar applications pose the benefit of entering the plant and potentially reacting more rapidly with the biological processes than if they were applied to the soil. Foliar applied biostimulants that have shown benefits to grapes include chitosan, which improved postharvest grey mold infections equally as well as synthetic fungicide applications (Romanazzi et al. 2006). Chitosan was also shown to protect against downy mildew (Romanazzi et al. 2016), which is a devastating disease that impacts foliage and fruit. Some studies have shown improved anthocyanin concentrations, which are an important component of grape and wine color. Foliar seaweed applications increased levels of anthocyanins and phenolics (Frioni et al. 2018), both important characteristics of wine. Another study showed that methyl jasmonate and yeast increased anthocyanins in Tempranillo grapes and wine when applied foliarly (Portu et al. 2016). Methyl jasmonate is a plant growth regulator and an elicitor, a type of organic biostimulant that can induce the synthesis of phenolic compounds, which then triggers defense reactions (Gutierrez et al. 2019). Methyl jasmonate is one of the most effective elicitors, but its use can be cost prohibitive.

Although biostimulants have been available for some time, and researched since the mid-seventies, more research is needed before conclusions are drawn on perennial crops. The multitude of products manufactured under the biostimulant umbrella, and their unique impacts on the numerous US perennial crops grown in different climates, necessitates multiple years of research to better understand their benefits.

On-Farm Research Trials

Growers interested in biostimulant products are encouraged to test them in their own vineyards. They should work closely with a Certified Crop Advisor (CCA), Pest Control Advisor (PCA) or university extension advisor to identify what plant health problem needs to be solved (i.e. improved nutrient uptake). On-farm trials should be designed so they can be repeated over multiple years and help determine if they improve production and solve the problem of interest. When possible, a trial site that reduces variables that may impact results should be chosen. For example, if improved nutrient assimilation is the goal, a trial site that has a consistent soil type would produce the best results by eliminating soil as a variable. Clay verses sandy soils retain nutrients differently and will impact plant nutrient and water uptake. Select products that claim to solve or improve a problem that has been experienced at a location over several years. Do not attempt to evaluate too many different products at once since it will make trial results more difficult to interpret. A “grower standard” is important to include so comparisons can be made against the experimental biostimulant regime. Collect data on the plant characteristics that you expect to see a change. For example, if the products being tested claim to improve yield or fruit quality, take fruit samples from each test block and compare them. If product claims are to improve plant nutrient absorption, collect leaves and/or petioles and have them analyzed by a commercial analytical lab. However, when collecting samples for data analysis, it’s important to be aware of edge or perimeter effects. Plants near edges of a plot tend to grow differently than plants in the middle of blocks that have competition for water or sunlight, and this can confound results. When possible, implement a replicated on-farm trial so that you have multiple locations to review treatments. If results from a replicated trial are consistent, that is a good indication that the biostimulants are the cause.

Contact a local CCA, PCA or university extension advisor to help design the trial, decide what data needs to be collected and interpret the results so the best information is gathered from an on-farm research trial.

More Information

To learn more about the use of biostimulants you can visit the Biological Products Industry Alliance (BPIA) website: https://www.bpia.org/ BPIA is an organization with membership from manufactures of various biostimulant products. Their focus is “advancing sustainability through biological solutions”, working with regulators to improve product registration and distribution and to educate producers on products and their best use for different crop production systems.

References

Calvo P, Nelson L, Kloepper JW. 2014. Agricultural uses of plant biostimulants. Plant Soil 383(1-2):3-41. https://doi.org/10.1007/s11104-014-2131-8
Frioni T, Sabbatini P, Tombesi S, et al. 2018. Effects of a biostimulant derived from the brown seaweed Ascophyllum nodosum on ripening dynamics and fruit quality of grapevines. Scientia Horticulturae. 232:97-106. https://doi.org/10.1016/j.scienta.2017.12.054
Gutiérrez-Gamboa G, Romanazzi G, Garde-Cerdán T, Pérez-Álvarez EP. 2019. A review of the use of biostimulants in the vineyard for improved grape and wine quality: effects on prevention of grapevine diseases. J Sci Food Agric. 99(3):1001-9. https://doi.org/10.1002/jsfa.9353
Heacox L. 2018. Biostimulants gaining ground. CropLife. https://www.croplife.com/special-reports/biologicals/biostimulants-gaining-ground/
Hilton S. 2019. Are biofertlizers actually effective? Team-Trade. https://blog.teamtrade.cz/are-biofertilizers-actually-effective/
Portu J, López R, Baroja E, et al. 2016. Improvement of grape and wine phenolic content by foliar application to grapevine of three different elicitors: methyl jasmonate, chitosan, and yeast extract. Food Chem. 201:213-221. https://doi.org/10.1016/j.foodchem.2016.01.086
Pucci J. 2018. What’s really behind the biostimulant boom. AgriBusiness Global.
https://www.croplife.com/crop-inputs/micronutrients/whats-really-behind-the-biostimulant-boom/
Romanazzi G, Nigro F, Ippolito A, et al. 2006. Effects of pre and postharvest chitosan treatments to control storage grey mold of table grapes. J. Food Sci. 67: 1862-1867. https://doi.org/10.1111/j.1365-2621.2002.tb08737.x
Romanazzi G, Mancini V, Feliziani E, et al. 2016. Impact of alternative fungicides on grape downy mildew control and vine growth and development. Plant Dis. 100(4):739-748. https://doi.org/10.1094/PDIS-05-15-0564-RE

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