Studies show biostimulants have benefits to crop health and yield in strawberries (photo by M. Katz.)
The 2018 Farm Bill describes a plant bio stimulant as a substance or microorganism 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.
Grower use of biostimulant products in strawberry production continues to increase, reports Surendra Dara, UCCE farm advisor and strawberry researcher based in San Luis Obispo County.
Used in addition to a standard nutrition program, beneficial microorganisms or substances have been shown to build soil structure, add to microbial diversity and stimulate resistance to pathogens. Use of biostimulant products can also allow for reduction in amount of applied macro nutrients.
The products can be applied to the soil after fumigation to repopulate soil with beneficial microbes as well as at planting time or to treat transplants prior to planting. Dara said when biostimulants are used in strawberry crops, they are typically applied multiple times throughout the season .
Application rates and frequency will vary according to the product formulations and the active ingredients. Biostimulant products can be applied via a drip system or as a foliar spray.
According to Dara, when plants are exposed to pests, pathogens, abiotic stressors, or beneficial microbes, defense genes are activated through two major immune responses, helping plants fight real infection or prepare them for potential infection. Biostimulant products induce plant resistance to stress factors through systemic acquired resistance or induced systemic resistance. Dara compares the beneficial microbes and non-microbial biostimulants to vaccines that prepare plants for potential health challenges.
The 2018 Farm Bill included statutory language and a formal regulatory framework to ensure a review process and uniform national labeling of agricultural bio stimulant products. The bill was also the first federal recognition of biostimulant products as emerging technology for production agriculture.
Biostimulant products are generated with the capture of microorganisms from soil or plant samples. They are grown in lab cultures and tested for their ability to improve the growth of crop seedlings. Much like new varieties of a crop, the most promising microorganisms advance to field trials. If successful, the microorganism can be directed for approval and production.
Dara’s studies in tomato and strawberry demonstrated varying levels of benefits to crop health and yield improvements from a variety of botanical, microbial, or mineral biostimulants and other supplements. Some of the evaluated products resulted in significant yield improvement in both tomatoes and strawberries compared to the grower standard practices. There are several biostimulant products in the market with a variety of active ingredients, and some also have major plant nutrients such as nitrogen, phosphorus, and potassium. Depending on the crop, growing conditions, potential risk of pests and diseases, and other factors, growers can use one or more biostimulant products.
This soft scale citrus pest has not been found in significant numbers in the San Joaquin Valley for the past several years, but cooler and wetter weather in April could mean a higher infestation rate this year. Mild weather maximizes egg hatch and helps nymphs survive.
Dr. Beth Grafton Cardwell, director of the Lindcove Research Center and research entomologist at UC Riverside, presented information about citricola scale in a webinar for growers and pest control advisors.
Control of citricola scale is a numbers game, Grafton-Cardwell said. Not letting populations get large before taking action is important. Damage thresholds are low and citricola scale numbers can expand quickly under the right conditions. Severe infestations in citrus can reduce tree vigor, flowering and fruit set. Citricola also excretes honeydew and sooty mold accumulates, interfering with photosynthesis.
High numbers of scale observed in the spring can have a negative effect on the next year’s yield.
Citricola scale produces one generation per year. Eggs, first instar nymphs, second instar nymphs and adult females are present at different times of the year.
Citricola scale females lay more than 1,000 eggs from early May to August. Crawlers emerge after two to three days and move to the underside of leaves. These flat, and almost translucent scales molt once and by November turn a darker color and begin migrating to twigs late winter and early spring, maturing to adults by late April.
Lifescycle of citricola scale (courtesy E. Grafton-Cardwell, UCCE.)
The best time to treat scale infestations is late July to early August when the scales have hatched and moved onto leaves. They are vulnerable to pesticide treatments, heat and some parasitoids.
Identification of the scale condition is important in the monitoring process. Only healthy scale are counted. To sample for scale, collect leaves from northeast corner of the tree, choosing leaves that are shaded. One leaf per tree should be collected down the row until 25 leaves are collected. Leaves infested with live scale are counted and the procedure repeated in four evenly spaced rows in the orchard.
The decision to treat is based on numbers. A count of more than 12 infested leaves per row warrants a treatment. Treatment will be most effective when crawlers move out onto leaves. Coverage is critical because insecticide must contact the crawlers. Slower spray speed is advised. The neonicotinoids Assail and Sivanto are most effective, but continued use of products from that group will allow resistance to develop. Insect growth regulator buprofezin will suppress citricola scale during the season it is applied.
The UC IPM guidelines report that about 40 percent of the citricola scale populations in the San Joaquin Valley have developed resistance to organophosphate insecticides
Increased Acreage and Improved Yields Cited as Reason for Record Production
Click here to view the 2020 Subjective Forecast View the Almond Board of California’s full news release below or at Newsroom.Almonds.com
MODESTO, Calif. – The U.S. Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) is predicting a record California almond crop for the third straight year. The USDA-NASS 2020 California Almond Subjective Forecast estimates California almond orchards will produce 3.0 billion pounds of nuts this year, up 17.6 percent from last year’s 2.55 billion-pound crop. Forecasted yield is expected to reach 2,380 pounds per acre, 10.2 percent greater than the 2019 yield of 2,160 per acre.[i]
This forecast comes about three weeks after USDA-NASS released the 2019 California Almond Acreage Report, which estimated total almond acreage for 2019 up 10 percent from 2018 at 1.53 million acres. Bearing acres – orchards mature enough to produce a crop – were reported at 1.18 million acres, up 8 percent from the previous year. USDA-NASS also estimated preliminary bearing acreage for 2020 at 1.26 million acres.[ii]
“Almond acreage and production continue to increase as California almond growers further invest in precision agriculture and responsible best practices,” said Almond Board of California (ABC) President and CEO Richard Waycott. “Through the industry’s advancements in water use efficiency to environmentally friendly pest management, zero waste efforts in the orchard and beyond, almond growers are committed to achieving our Almond Orchard 2025 Goals and the realization of the California almond orchard of the future.”
The first of two production reports for the upcoming crop year, the Subjective Forecast is based on opinions obtained from randomly selected almond growers located throughout the state via a phone survey, this year conducted from April 20 to May 6. USDA-NASS asks individual growers to indicate their total almond yield per acre from last year and expected yield for the current year based on field observations. The sample of growers interviewed is grouped by size of operation, and different individuals are interviewed each year to ensure grower representation throughout the Central Valley. USDA-NASS then combines the yield estimates obtained from each grower and extrapolates the information to arrive at the numbers reported in the Subjective Forecast.
This July, USDA-NASS will release its second production estimate, the 2020 California Almond Objective Report. While the Subjective Forecast provides an initial estimate of the 2020/2021 crop, the Objective Report will provide an estimate based on actual almond counts that uses a more statistically rigorous methodology to determine yield.
In Dec. 2019, ABC’s Board of Directors approved a strategic approach to further improve the accuracy of USDA-NASS’s reporting. From 2020 on, the Objective Report will include measurements from 1,000 target orchards throughout the state (an increase of 150 samples from 2019) and provide nut counts on not one but two branches per tree. The Objective Report will also provide the weight, size and grade of the average almond sample broken down by growing region – no longer growing district – and variety.
The 2020 California Almond Objective Report will be released on Tuesday, July 7, at 12:00 p.m. PT. USDA-NASS conducts the Objective Report, the Subjective Forecast and the Acreage Report to provide the California almond industry with the data needed to make informed business decisions, and thanks all farm operators, owners and management entities for their time in providing the information necessary to create these reports.
__________________________________ [i] USDA-NASS. 2020 California Almond Subjective Forecast. May 2020. [ii] USDA-NASS. 2019 California Almond Acreage Report. April 2020.
DENVER & Research Triangle Park, NC – May 5th, 2020 – Wilbur-Ellis, a recognized leader in precision agriculture, crop protection, seed, nutritional and biological products, in cooperation with Vestaron Corporation, announced today a distribution agreement to semi-exclusively distribute SPEAR-LEP, an innovative bioinsecticide manufactured by Vestaron.
SPEAR-LEP® is a peptide-based bioinsecticide that has the superior safety profile of a biological product, but with the efficacy and specificity of a synthetic product for broad spectrum lepidopteran control on tree fruit, nuts, vines and vegetables. Acting at the same receptor but different site as neonicotinoid & Spinosad chemistries, this IRAC Group 32 biological product offers a novel mode of action and an incredible resistance management tool for the stewardship of certain major synthetic chemistries while still allowing growers to maintain biological safety profiles and control lepidopteran pests in their apple and almond orchards.
Jesse Rosales, key actives and biopesticides portfolio manager for Wilbur-Ellis, said, “We evaluated SPEAR-LEP® in several apple and almond field trials in 2019 and were very pleased with the results. Our salespeople and growers were particularly interested in the potential for a biopesticide without MRLs (Maximum Residual Levels) that is able to be used close to harvest or in the peak of the season, in order to save some of their heavier chemistries.”
SPEAR-LEP® has been evaluated in 60+ field trials across North America and has consistently controlled pests equivalent to mainstream synthetic chemistries. SPEAR-LEP® carries many of the same features of biopesticides such as a 0-day Preharvest Interval (PHI), 4-hour Restricted-Entry Interval (REI) and Caution signal word.
Said Rosales, “SPEAR-LEP® is the kind of biopesticide we think can enter mainstream ag in the almond and apple markets. We’re looking forward to our continued evaluation and sales in 2020.”
Vestaron Senior Vice President of Sales and Marketing Ben Cicora said, “Vestaron sees this new partnership with Wilbur-Ellis as a critical milestone for our U.S. commercialization efforts with Spear-Lep®. Growers are looking to Wilbur-Ellis for new progressive solutions in these markets and Spear-Lep® is the first of many new active ingredients in the coming years.”
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This press release is intended for informational use only and cannot be used as a replacement for a product label. Any products mentioned in this press release may only be sold in states where they are registered or where registration is not a factor. Please contact your local Wilbur-Ellis representative for more information.
About the Wilbur-Ellis Companies
Founded in 1921, the Wilbur-Ellis companies are leading international marketers and distributors of agricultural products, animal feed and specialty chemicals and ingredients. By developing strong relationships, making strategic market investments and capitalizing on new opportunities, the Wilbur-Ellis companies have continued to grow the business with sales now over $3 billion. wilburellis.com
Wilbur-Ellis Agribusiness generates more than $2 billion in sales revenue annually and has over 160 branch locations throughout the U.S. ag.wilburellis.com
About Vestaron:
Vestaron is a company dedicated to improving the safety, efficacy and sustainability of crop protection through migration from synthetic pesticides to peptide-based biopesticides. Vestaron is initially focused on a class of peptides that kill insect pests efficiently, but are safe for humans, beneficial insects and the environment. As part of this, the company has developed a proprietary platform for peptide optimization, fermentation-based peptide production that will allow it to develop a wide variety of biologic crop protection solutions. Vestaron is the winner of the inaugural 2015 Bernard Blum Award for novel biocontrol solutions and a 2020 THRIVE Top 50 Growth-Stage honoree.
DURHAM, NC (May 5, 2020) —The California Department of Pesticide Regulation has recently granted SEICAN biopesticide registration approval for use in the state.
This approval brings to California growers an OMRI-listed miticide-insecticide that is highly effective against multiple pests with high economic impact on the wide variety of crops grown in the state.
“SEICAN is broad spectrum biopesticide based on cinnamaldehyde,” explained Jim Sturges, Summit Agro Western Regional Sales Manager. “SEICAN acts quickly to provide high efficacy at low doses and is ideally suited for conventional, sustainable, and organic farming programs.”
With dual modes of action SEICAN acts by contact on target pests with a repellant effect that prevents new infestations. This new biopesticide offers California growers an excellent alternative to mineral oils and chemical acaricides, Well-suited for resistance management programs, SEICAN also presents a 0-day pre-harvest interval.
Further information on SEICAN can be found at summitagro-usa.com.
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About Summit Agro USA
Summit Agro USA, located in Durham, NC, is focused on working with our partners to identify, develop, and deliver innovative solutions that meet the needs of growers across the United States. Summit Agro has a history of bringing innovative solutions to market and can manage the full process from initial development to sales. This integrated business approach enables us to provide reliable, high-quality products to US growers. Whether the need is for insecticides, fungicides or herbicides, Summit Agro has a full range of product offers to meet the needs of our customers.
WASHINGTON, April 28, 2020 –The U.S. Department of Agriculture (USDA) announced today a $15 million investment to help support the adoption of innovative conservation approaches on agricultural lands. USDA’s Natural Resources Conservation Service (NRCS) is accepting proposals through June 29, 2020, for national Conservation Innovation Grants (CIG). CIG projects inspire creative problem-solving solutions that boost production on farms, ranches and private forests and improve natural resources.
This year’s priorities are water reuse, water quality, air quality, energy and wildlife habitat.
“Through Conservation Innovation Grants, we’re able to co-invest with partners on the next generation of agricultural conservation solutions,” NRCS Chief Matthew Lohr said. “Conservation Innovation Grants have helped spur new tools and technologies to conserve natural resources, build resilience in producers’ operations and improve their bottom lines. This year will be the first time we are offering water reuse as a priority, and we’re excited to see how these projects play a role in USDA’s broader strategy for water reuse on agricultural land.”
National CIG
CIG is a competitive grants program that supports development, testing and research of conservation technologies, practices, systems and approaches on private lands. Grantees must match the CIG investment at least one to one.
All U.S.-based non-Federal entities and individuals are eligible to apply. Complete funding announcement information can be accessed through the Conservation Innovation Grants webpage.
The National CIG program supports early pilot projects or demonstrations of promising conservation approaches and is distinct from the $25 million announced on March 12 for On-Farm Conservation Innovation Trials. On-Farm Trials is a separate CIG component created by the 2018 Farm Bill. It includes a Soil Health Demonstration Trial.
State NRCS CIG
State NRCS offices are also able to fund and hold their own CIG competitions in addition to the National CIG signup. Please visit NRCS state office websites for information about state CIG competitions.
More Information
NRCS’s CIG program is identified in the federal government’s National Water Reuse Action Plan as an opportunity to support development of innovative projects that focus on water reuse on private lands. Read this April 28 post on the USDA Blog for how USDA is working with the U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration, Department of Interior, Department of Energy and others to promote water reuse across sectors.
CIG applications must be submitted through Grants.gov by 11:59 p.m. EDT on June 29, 2020. A webinar for potential applicants is scheduled for 3 p.m. EDT on May 13, 2020. Information on how to participate in the webinar is posted on the CIG website.
CIG also contributes to the Agriculture Innovation Agenda: a USDA initiative to align resources, programs, and research to position American agriculture to better meet future global demands. Specifically, USDA is working to stimulate innovation so that American agriculture can achieve the goal of increasing production by 40 percent while cutting the environmental footprint of U.S. agriculture in half by 2050.
WASHINGTON, April 20, 2020 – USDA’s Natural Resources Conservation Service (NRCS) today announced it will extend deadlines for project proposal submissions to May 29 for On-Farm Conservation Innovation Trials and the Regional Conservation Partnership Program (RCPP) Alternative Funding Arrangements (AFAs). Originally deadlines were mid-May, but NRCS wanted to provide additional time because of the coronavirus pandemic.
“NRCS recognizes the hardship that this unprecedented time is causing our partners and others,” said NRCS Chief Matthew Lohr. “We want to offer them additional time to take full advantage of these opportunities to propose bold and transformative projects to advance agriculture and conservation for present and future generations of agricultural producers and private forest landowners.”
NRCS will invest up to $50 million in fiscal year 2020 to fund AFAs, a unique and partner-led approach to address natural resource concerns at local, regional and landscape scales. NRCS is authorized to fund up to 15 projects in which partners will receive greater liberty to manage an RCPP project and the associated relationships with participating producers and landowners. Funding for projects will range from $250,000 to $10 million.
Through AFAs, approved project partners can work directly with farmers, ranchers and private forest landowners to carry out RCPP projects, instead of implementing projects through NRCS producer contracts and landowner easements.
The 2018 Farm Bill highlighted some project types that are particularly suited to AFAs:
Projects that use innovative approaches to leverage the federal investment in conservation;
Projects that deploy a pay-for-performance conservation approach; and
Projects that seek large-scale infrastructure investments that generate benefits for agricultural producers and nonindustrial private forest owners.
Additionally, NRCS will invest up to $25 million in On-Farm Trials in 2020, which are a component of the Conservation Innovation Grants (CIG). This investment will help support the adoption and evaluation of innovative conservation approaches on agricultural land. This includes up to $10 million for the Soil Health Demonstration Trials. On-Farm Trials funding is designed to offer producers, through partners, technical and financial assistance compensation for any risks associated with carrying out new conservation practices, systems and approaches at the farm level, including the environmental, financial and social (to the extent possible) impacts of carrying them out.
NRCS is seeking proposals that address at least one of the following four On-Farm Trial main priorities:
Irrigation Management Technologies;
Precision Agriculture Technologies and Strategies;
This breakthrough technology, for both conventional and organic growers, is a first for the agricultural industry.
Boca Raton, FL, April 17, 2020 — Attune Agriculture, a unique leader in the industry combining food and agricultural science, announces that its OMRI listed adjuvant, Ampersand®, is now available for sale and use in California. Ampersand is made with only food-grade ingredients, and works differently than other adjuvants currently on the market to maximize the efficacy of herbicides and insecticides. This technology is the first of its kind for the agricultural industry.
Ampersand is not a surfactant. In fact, tank sprays with Ampersand are designed to have droplets with a high surface tension and high contact angle, the opposite of how other adjuvants are engineered. Attune’s patented technology starts to control droplets at the nozzle using humectant and hydrocolloid properties that regulate droplet size and improve deposition. Once the droplets are on the leaf, ingredients that provide adhesion prevent droplets from rolling off the leaf, or bouncing and shattering. Ampersand also gives actives more time on the leaf to perform their functions by reducing evaporation, drying and wash off.
The result is a game-changing tank mix partner that delivers three times more spray to the leaf, two times the absorption potential, and four times the wash off protection. Not only does Ampersand have the lowest toxicity rating, Category IV, no signal words are required for labeling, and no special PPE or handling is required. Despite its fit for organic use, Ampersand provides cost effective performance benefits for conventional applications as well.
Extensive testing has shown that Ampersand improves weed control by an average of 79% when combined with a leading organic herbicide. With respect to sprayable pheromones, Ampersand has been shown to increase the efficacy by 45%. Additional studies have demonstrated that glufosinate can be improved by 51% with the addition of Ampersand to the tank mix.
“Now, more than ever before, every spray matters,” says Greg Andon, CEO of Attune. “We are excited to introduce Ampersand to California growers, where we can help boost the performance of organic actives to levels approaching conventional, and improve conventional actives to levels never seen before.”
Ampersand is available through distribution by Buttonwillow Warehouse Company and Grow West for the California market.
About Attune Agriculture, Inc. Born from over 100 years of hydrocolloid expertise, Attune Agriculture combines deep roots in food science and agriculture to create products dedicated to providing the world with agricultural tools that are both performance-based and safe for the environment and the people who use them. For more information, please visit www.attuneag.com.
To survey and molecularly identify Fusariumoxysporum f. sp. vasinfectum (FOV) races and other seedling and wilt pathogens in commercial and grower cotton fields in California.
To further evaluate the seedling and wilt capabilities of FOV races with different inoculation methods using susceptible and resistant Pima and Upland germplasm.
To further evaluate the interactions of different FOV races and Rhizoctonia solani and their impact on disease development in cotton.
Additional match funding has been approved from the California State University Agricultural Research Institute (ARI) for both years of the project thanks to support letters provided by CCGGA and Cotton Inc. With the additional funding, we were able to expand on our current proposed work and add the following objectives to the ARI proposal.
To use representative identified FOV races for phenotypic evaluation of selected Upland cotton germplasm
To determine the effects of pH, temperature, and moisture on disease development in cotton when inoculated with FOV4.
Objective 1: To survey and molecularly identify Fusarium oxysporum f. sp. vasinfectum (FOV) races and other seedling and wilt pathogens in commercial and grower cotton fields in California.
Prior to this proposal, Fusarium isolates were collected in 2017 and 2018. Isolate information is provided in Table 1. All isolates were identified using two PCR assays and DNA sequencing of the translation elongation factor (EF-1α) gene. The first PCR assay produced a 208 bp amplicon unique to FOV races 3, 4, and 7, while the second multiplex PCR assay genotyped FOV isolates into two genotypes, N (396 bp), and T (583 bp). These genotypes were identified based on the absence (N type) or presence (T type) of the insertion of the transposable element Tfo1 in the phosphate permease (PHO) gene unique to FOV race 4. Although not shown these isolates have been genotyped with newly developed primers. We are repeating the genotyping currently for verification of results.
Table 1: Isolates of Fusarium collected in seven locations in the San Joaquin Valley of California in 2017 and 2018.
For the current proposed research, 11 locations across the San Joaquin Valley and six locations in the El Paso, Texas region were sampled beginning in mid-May 2019. To date, single spore isolations for 110 Fusarium isolates have been completed (Table 2). All isolates were collected from symptomatic cotton seedlings. Additionally, 18 isolates of Rhizoctonia solani were also isolated from symptomatic cotton seedlings (Table 2). Other fungal species were isolated and are currently being identified morphologically. It appears that there may be some additional Fusarium species that are not FOV. Isolates will be genotyped similar to 2017 and 2018 isolates.
Table 2: Isolates of Fusarium spp. and Rhizoctonia solani collected in 2019
A preliminary baiting method using collected soil from a cotton field in Dos Palos, Calif. was completed. This assay was modified for the isolation of Pythium spp. from field soil using soybean as bait. From this assay isolates of what appear to be FOV, Pythium, and R. solani were all baited using the susceptible Pima cultivar DP-340. Soil has been collected from a number of locations across CA and will be used in the baiting method to isolate other potential pathogens not isolated from collected plant material. Soil samples from some of the first locations where FOV race 4 was identified in CA but are no longer in production for cotton were also collected. This assay might allow us to determine if the pathogen FOV race 4 is still present in these locations, despite being out of production for at least a decade in some cases.
Two undergraduate students have been trained and have been conducting the work mentioned above under the guidance of Dr. Ellis and her previous graduate student. Another student has also started to isolate DNA from the single spore isolations for identification using new PCR primers. Additionally, DNA sequencing of isolates will be done using the translation elongation factor and internal transcribed spacer region.
Objective 2: To further evaluate the seedling and wilt capabilities of FOV races with different inoculation methods using susceptible and resistant Pima and Upland germplasm.
Three assays will be compared to further evaluate seedling and wilt capabilities of FOV races/genotypes. A rolled towel assay was developed in our lab, and will be compared to the root-dip inoculation method and an infested-oat-seed method that was modified from a protocol by Beccera et al. (2012). Protocols for these methods have all been established and tested in preliminary studies. A rolled towel assay using eight representative Fusarium isolates was completed to evaluate possible variation in aggressiveness towards cotton by different FOV4 genotypes and F. solani isolates. The assay was set up using Pima cultivar DP-340. The results from two runs of the assay are provided in Figure 1 and 2, below. There was a significant difference among isolate and experiment (P<0.0001), but there was not a significant difference for the interaction for isolate and experiment.
To calculate the disease severity index (DSI), lesion length and total plant length were measured with a ruler for each seedling and then the lesion length was divided by the total plant length and multiplied by 100. Seed that did not germinate and were colonized by FOV were given a 100% index rating (Ellis et al., 2011).For the ordinal scale a 1-to-5 scale was used, where 5 = no germination, complete colonization of the seed; 4 = germination, complete colonization of the seed, and 75% or more of the seedling root with lesions; 3 = germination, some colonization of seed, and 20 to 74% of the root with lesions; 2 = germination, little colonization of the root, and 1 to 19% of the root with lesions; 1 = germination, healthy seedling with no visible signs of colonization.
Additionally, these same isolates or a similar set will be used in the comparison of different greenhouse assays. We plan to use varieties of both Pima and Upland cotton with varying levels of plant host resistance in the assays. Finally, we have started to screen previous isolates collected from 2017 and 2018 using the root dip inoculation method. This will also be done for a majority of isolates collected in 2019. Once pathogenicity for the majority of the isolates is tested using the root dip assay and genotyping is completed a representative set of isolates can be used in our screening efforts.
Objective 3: To further evaluate the interactions of different FOV races and Rhizoctonia solani and their impact on disease development in cotton.
The graduate student for this objective has been currently evaluating environmental parameters of our CA FOV and R. solani isolates such as pH and temperature. Infested-oat inoculum has been prepared to begin the interaction study with FOV race 4 and R. solani. Furthermore, we also plan to co-inoculate with different FOV race 4 genotypes and F. solani.
Field bindweed in cotton in Merced County (2019).
(Photos courtesy of L. Sosnoskie)
Cotton is susceptible to weed interference, especially following emergence, as many weed species can outgrow and outcompete the newly germinated seedlings. This includes a weed native to California – Palmer amaranth (Amaranthus palmeri)- whose season-long germination phenology and high rate of photosynthesis enhances its ability as a crop competitor. Palmer amaranth interference significantly affects the growth and yield of most agronomic crops, with cotton being one of the more sensitive commodities. In addition to direct impacts on yield, Palmer amaranth can also interfere with harvest efficiency. Research has suggested that mechanical harvesting of cotton with Palmer amaranth at densities greater than six plants per 30 feet of row was impractical because of the potential for damage to equipment. Additional reports noted that the frequency of work stoppages increased as Palmer amaranth densities increased because of the need to repeatedly dislodge weed stems from the harvester.
Figure 1b. Palmer amaranth infestation in an almond orchard in Merced County (2019).Figure 1a. Glyphosate-resistant Palmer amaranth in cotton in Madera County (2019).
Currently, glyphosate is the predominant herbicide applied in California cotton for weed control. According to data derived from the California Department of Pesticide Regulation (CDPR) pesticide use reports, glyphosate was applied to 438,305 cotton acres in 2016, which is eight times more treated acreage than the next most commonly applied active ingredients (paraquat and oxyfluorfen). The use of glyphosate is not limited solely to cotton; glyphosate is an important component of weed control programs in a diverse array of crops, including almonds, alfalfa, corn, grapes, pistachios, and walnuts. The extensive use of glyphosate across commodities and over time has resulted in the selection for glyphosate-resistance in six species in California, including Palmer amaranth (Figures 1a and 1b, above).
Pesticide use reports indicate that California cotton growers do not regularly use residual herbicides on their planted acres; pendimethalin and flumioxazin were applied to less than half of California’s cotton acres in 2016, suggesting that growers are relying, heavily, on post-emergence measures (including glyphosate, hand-weeding, and cultivation) for weed control. Palmer amaranth has an exceptionally high growth rate, which allows the species to rapidly exceed height limits for chemical control. For example, glufosinate applications should be made to small (<3” in height) Palmer amaranth to prevent weed escape and regrowth.
In 2019, a trial was undertaken in Fresno, Calif., to describe the growth of Palmer amaranth in response to emergence date and to determine how quickly Palmer amaranth can overcome most herbicide label height limits. Palmer amaranth seed was collected in September of 2018 from a population growing alongside an agronomic crop field in Merced County. Seed were planted into 1.7-gallon pots containing all-purpose garden soil on April 21, April 28, May 30 and June 18, 2019. Palmer amaranth emerged on April 24th, May 2, June 2 and June 21 and were thinned to a density of one plant per pot (10 pots total per planting date). Palmer amaranth growth and development was recorded for each individual pot every second day until 20 days after emergence (DAE). Growing degree days (GDD) were calculated for each observation window using UC IPM models and Palmer growth regressed against GDD to predict critical stages (3 and 6 inches in height) for Palmer management.
All Palmer amaranth in this study reached a height of 3 inches by six to 10 DAE (Figure 2, below). Palmer emerging on April 24th and May 2nd reached a height of six inches 14 to 16 DAE, whereas Palmer amaranth emerging on June 2nd and June 24th reached a height of 6 inches 12 DAE. Plant heights at 20 DAE were 11.5, 8.5, 20.0 and 21.3 inches for the April 24th, May 2nd, June 2nd and June 21st emergence dates, respectively.
Figure 2. Palmer amaranth height (inches) two to 20 DAE as affected by emergence date.
To standardize Palmer growth across all observation periods, plant heights were regressed against accumulated GDD using a second-order polynomial model; a threshold base temperature of 50 degrees F was used in the computation (Figure 3, below). Results indicated that the observed SJV Palmer amaranth population requires 175 to 180 GDD to achieve a height of 3 inches and 270 to 275 GDD to reach a height of 6 inches. This model can serve as a basis for predicting Palmer amaranth development in the future. Understanding the relationship between the accumulation heat units and plant growth makes it possible to predict when Palmer could become too large for control during a growing season regardless of yearly variation in temperature.
Figure 3. Palmer amaranth height (inches) regressed against GDD. Y = 5E-05×2 + 0.0084x – 0.0247 where Y = inches and x = GDD.
If Palmer amaranth escapes herbicide (or cultivation) treatments, hand-weeding may be needed to prevent Palmer amaranth from producing seed that can be returned to the soil seedbank. Remember: female Palmer amaranth can produce up to a million seed per plant, which can support an infestation for many years to come. When hand-weeding, plants should, ideally, be removed entirely from the field to prevent them from becoming re-established. Even plants that are cut off at or near the base of the stem can re-sprout and achieve reproductive maturity.
Escapes are not uncommon as Palmer amaranth can grow rapidly and outpace many control efforts. If plants become established in the field and hand-weeding is necessary, be sure to remove as much of the weed biomass as possible to prevent plants from growing and achieving reproductive maturity.
Field Bindweed Perennialization
Field bindweed (Convolvulus arvensis) is another species that has become problematic in California cotton, particularly in crop rotation systems that are characterized by drip irrigation and reduced tillage. In addition to negatively impacting cotton yield, bindweed can serve as an alternate host for the silverleaf whitefly, the honeydew from which is a primary source of sugars that can result in sticky cotton lint.
Field bindweed is a deep-rooted (up to 20 feet) and spreading perennial vine, Management guidelines often suggest that field bindweed is susceptible to control at the seedling stage, although there is limited information to suggest when newly emerged field bindweed vines assume the characteristics of perennial plants. Personal communications between weed scientists have indicated that field bindweed seedlings could survive defoliation attempts as soon as 3 WAE.
Field bindweed in cotton in Merced County (2019).
In 2019, a trial was undertaken in Fresno, Calif., to describe the growth of seedling field bindweed and to determine when the vines take on the characteristics of perennial plants; specifically, the study was designed to evaluate at what stage field bindweed can regrow from root buds following above-ground biomass removal. Field bindweed seed collected in Merced County in 2018 was scarified using boiling water to induce germination. Seed were planted into 1.7-gallon pots containing all-purpose garden soil on April 17 and June t, 2019, representing two runs of the trial. Bindweed emerged on April 20 and June 4, respectively. Four replicate bindweed seedlings were physically defoliated (by removing all aboveground biomass at the soil line) at either 2, 4, 6, or 8 WAE and their compensatory growth measured two weeks after the cutting treatment (WAT). A second set of seedlings were destructively harvested at 2, 4, 6, and 8 WAE to describe biomass accumulation at the time of cutting.
Results indicate that the ability of field bindweed to regrow following defoliation increased with plant age (Table 1, see below). Field bindweed seedlings defoliated at 2 WAE did not re-sprout by two weeks following cutting; no viable above- or below-ground tissue was observed and recorded. Thirty-eight percent of field bindweed seedlings defoliated at 4 and 6 WAE survived the cutting treatment and re-sprouted. One average, 0.5 to 3.0 grams of stem/leave and root tissue were recovered at 2 WAT. One hundred percent of the field bindweed defoliated at 8 WAE survived the cutting treatment and produced 13.1 and 35.9 grams of above- and below-ground tissue, respectively.
While most management practices are focused on controlling rhizomatous vines, the seed of field bindweed should not be ignored. Bindweed seed can remain viable in the soil for decades (Weaver and Riley 1982) suggesting that infestations can re-occur even if rhizomes are successfully eradicated from a site. Anecdotal evidence indicated that newly emerged seedlings could take on the characteristics of perennial vines, rapidly, following germination. Results from this study suggest that field bindweed seedlings may not remain sensitive to certain control measures for more than 4 weeks after emergence. Studies to examine seedling development and responses to contact and systemic herbicides will be conducted during the fall of 2019/winter of 2020.
Field Bindweed Response to Trifluralin and Pendimethalin
Results from previous studies in processing tomatoes have shown that trifluralin pre-plant incorporated (PPI) can suppress perennial field bindweed vines (Sosnoskie and Hanson 2015). However, most cotton growers do not regularly apply this active ingredient in their systems; with respect to pre-emergence herbicides, pendimethalin (which is in the same chemical family as trifluralin) is more commonly used.
Studies were initiated at the UC Westside Research and Extension Center in Five Points California in May 2019 to describe the response of field bindweed to trifluralin and pendimethalin relative to an untreated check. Trifluralin (24 oz/A Treflan) and pendimethalin (24 oz/A Prowl H2O) were applied on May 24 and physically incorporated to a depth of three inches. Individual plots were 13.5 feet in width and 50 feet in length. An untreated check (UTC) was also included. Bindweed pressure in the trial was considered to be significant; approximately half of the study site was covered in vines two weeks before the initiation of the trial. To ensure sufficient contact between the herbicide and the soil surface, the trial location was repeatedly disked to remove standing vegetation. Bindweed cover and flowering was assessed weekly from June 6 until July 16.
Figure 4. Bindweed cover (% of area occupied by vines) in response to trifluralin and pendimethalin.
Few pre-emergence or pre-plant incorporated herbicides are registered for the suppression of perennial field bindweed vines. Trifluralin, a dinitroaniline microtuble inhibitor, has been shown to inhibit vine emergence while pendimethalin has not. Results from the 2019 trial demonstrated that vine cover in the trifluralin treatments was reduced by 50 percent or more relative to the untreated check and pendimethalin treatments (Figure 4, above). There were no differences between pendimethalin and the UTC. By July 16, mean bindweed cover in the trifluralin plots was 45 percent, whereas cover in the pendimethalin and UTC plots were 88 percent and 93 percent respectively. Flowering didn’t commence until June 27 in all treatments (<1% – trifluralin, 11% – pendimethalin, 27% – UTC) (Figure 5, below). Trifluralin also reduced flowering potential on July 8; however, by July 16, 90 percent of emerged vines were flowering in all treatments. Pendimethalin and trifluralin control a similar spectrum of weeds; if field bindweed is a concern in a field, growers may want to consider the use of trifluralin for vine suppression.
Figure 5. Bindweed flowering (% vines flowering) in response to trifluralin and pendimethalin.
Continuing Research
A field trial to evaluate the combined effects of residual and postemergence herbicides and cultivation on vine control and cotton growth is ongoing and will be reported on at a later date. Results describing bindweed control in response to fall applied herbicides will also be presented later.
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