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.
The University of California Agricultural Issues Center (UC AIC) and the Department of Agricultural and Resource Economics at UC Davis work with UC Cooperative Extension Farm Advisors and Specialists to compile cost studies for crops and livestock produced in California. These costs and return studies are used by growers, bankers, crop consultants and many others to aid in a range of farm decisions from what to plant to production specifics. Often policy makers and researchers use these cost studies as well. The current and archived cost studies can be found at: https://coststudies.ucdavis.edu/
UC AIC recently released new cost and return studies for almond production in California. These 2019 regional cost and return studies for almonds are available for the Sacramento Valley, and the Northern and Southern San Joaquin Valley. This recent update of almond studies presents an opportune time to explore trends in almond cost and returns for the most recent two decades.
Before digging into graphs and figures, it’s important to discuss the elements of the cost study. The cost and return studies are meant to be used as a guide for growers, and actual costs and returns will vary depending on the specifics of the operation, growing conditions, and orchard characteristics. Therefore, it is necessary to specify underlying assumptions for orchards represented. It is not feasible to represent the infinite number of almond production scenarios out there. The following are some of the basic assumptions of 2019 cost study for the Northern San Joaquin Valley. For the full list of assumptions for each study listed in the charts, see the cost and return studies themselves.
The orchard consists of 100 acres of almonds with a density of 130 trees per acre.
No specific variety is listed.
The useful life of the orchard is expected to be 25 years.
A new micro-sprinkler irrigation system is installed during orchard establishment.
The expected yield at maturity is 2200 lbs per acre at an expected price of $2.50/lb.
Interest rates are 5.25% for operating loans and 6% for long-term investments.
Land value is $25,200 per producing acre.
Cost of pumping irrigation water from an established well is $100 per acre-foot.
Cost of pollination is 2 hives per acre at $200 per hive.
The cost studies go into detail about the following cost categories, and provide a look at costs and returns at various yield and price combinations.
Operating costs: Any costs associated with almond production practices in a given year, including pesticide and fertilizer applications, irrigation water, labor, harvesting, interest on operating loan.
Cash overhead costs: Expenses paid that are not for a particular enterprise and should be assigned to the whole farm operation, such as office and accounting expenses, assessments, field sanitation, or equipment repairs.
Non-cash overhead costs: Annual depreciation and interest cost for farm investments. Examples include depreciation on farm machinery, well/irrigation systems, annual establishment costs, etc.
Establishment costs: Total pre-plant, planting and accumulated costs for non-bearing years. Establishment costs are amortized (spread out) over the useful life of the orchard.
Total costs: Sum of operating, cash overhead, interest and non-cash overhead costs.
Looking over these cost studies can help growers and crop advisors make sure they are incorporating all costs when making crop production decisions.
Trends in Almond Costs
To outline the trends in almond production costs, I use the 1998, 2002, 2006, 2011, 2016 and 2019 UC AIC cost and return studies for establishing and producing an almond orchard in the Northern San Joaquin Valley using micro-sprinkler irrigation. This provides an approximate idea of how costs have developed over time. The trends in most cost categories should be similar across the state, however there may be noticeable differences in certain aspects across regions, ex: land values, water costs, etc.
Figure 1 displays per-acre costs of almond production over time. All costs are adjusted to 2019 dollars to account for inflation. It is clear from the figure that from 1998 to 2016, inflation-adjusted total costs of almond production remained similar at around $4,500 per acre.
Figure 1: Sample Per-Acre Costs of Establishing and Producing Almonds in the Northern San Joaquin Valley Using Micro-Sprinkler Irrigation, 1998, 2002, 2006, 2011, 2016, and 2019 (in 2019 dollars) Sources: University of California Agricultural Issues Center Sample Cost and Returns Studies: https://coststudies.ucdavis.edu/. US Bureau of Economic Analysis, GDP Price Deflator.
Between 2016 and 2019, total costs of almond production per-acre increased substantially (See Figure 1). The driver of this is a large increase in non-cash overhead costs. The primary increases in this cost category between 2016 and 2019 are increases in establishment costs and land values. Interest rates in 2016 were 3.25 percent compared with 6 percent in 2019, increasing establishment costs substantially. According to USDA National Agricultural Statistics Service, average irrigated land values in California increased by 8 percent on average from 2016 to 2019. Factoring land values into the cost of production allows growers to consider the opportunity cost of their investment in the almond orchard. Even if a grower owns the land he or she plans to establish an orchard on, he or she might be better off renting out the orchard and investing those rental revenues elsewhere.
Figure 2: Cost Categories as a Percentage of Total Operating Costs for Almond Production in the Northern San Joaquin Valley Using Micro-Sprinkler Irrigation, 2002, 2011 and 2019 Source: University of California Agricultural Issues Center Sample Cost and Returns Studies: https://coststudies.ucdavis.edu/
Operating costs per acre also increased between 2016 to 2019. Much of the increase in operating costs was due to increasing labor and pesticide costs, as well as increases in the operating loan interest rates. Figure 2 shows various cost categories as a percentage of total operating costs for 2002, 2011 and 2019 almond production. In 2002, pesticides, labor and harvest comprised more than 60 percent of total operating costs. While that number dropped to roughly 43 percent in 2019, over time, pollination, irrigation and fertilizer costs have increased to make up a much larger portion of total operating costs for almond growers. Irrigation costs may continue increasing as a percentage of total operating costs given implementation of the Sustainable Groundwater Management Act (SGMA), however it is unclear what the effects of this regulation will be (for SGMA resources see http://groundwater.ucdavis.edu/SGMA/). Pollination fees will likely continue their trend upward as well, though growers may be able to reduce pollination costs through decreasing the number of colonies per acre, planting self-fertile varieties or making mutually beneficial contractual arrangements with the beekeeper (Goodrich, 2019; Champetier, Lee, and Sumner, 2019).
Trends in Almond Returns
Figure 3: Planted Almond Acreage by Region and Nonpareil Average Base Rate ($/lb in 2019 dollars), 2004-2018 Sources: 2018 Almond Acreage Report, USDA NASS, CDFA. Blue Diamond Payment History 2004-2018. US Bureau of Economic Analysis, GDP Price Deflator.
Figure 3 shows the Blue Diamond average base rate for nonpareil meats from 2004 to 2018 (in 2019 dollars to adjust for inflation). Since 2016, prices have been lower than the 2004-2018 average of $3 per pound. Uncertainty in trade issues have resulted in decreased demand for almonds in a number of countries (Sumner, Hanon and Matthews, 2019). For example, almond exports to China were down 24 percent between 2018 and 2019 (Almond Board of California, 2019). This decreased demand has led to lower almond prices, and with future trade agreements still uncertain, it is unclear how prices will move going forward.
Figure 4: Variety Price as a Percentage of Nonpareil Price and Nonpareil Total Yield as Percentage of Butte/Padre, Butte, Monterey, Carmel, and Fritz Yield Sources: Blue Diamond Payment History 2013-2018. Almond Board of California Almond Almanac 2013-2019.
The prices a grower receives will vary by quality, size and variety. Figure 4 shows average variety prices as a percentage of nonpareil. In 2016 and 2017, other varieties were discounted fairly heavily in comparison to nonpareil, while in other years discounts were not quite as large. What impacts the size of these discounts? The relative supply and demand of nonpareil compared with other varieties. Figure 4 also displays nonpareil production as a percentage of total production from Butte/Padre, Butte, Monterey, Carmel, and Fritz. In 2017 and 2018, nonpareil production was relatively high compared to these other varieties. The large supply of nonpareil almonds drives down the price relative to other varieties, shrinking the associated premium.
Trends in Planted Acreage
Figure 3 also shows planted acreage from 2004 to 2018 by region along with the average price of nonpareil. The planted acreage trends by region look relatively similar. Over the last five years, the largest almond producing region (Southern San Joaquin Valley) has seen planted acreage drop off significantly. Water availability concerns as well as relatively low prices are likely the driving issues here. The Northern San Joaquin Valley has also seen acreage drop off, but not as substantially as its southern counterpart. Planting in the Sacramento Valley has stayed relatively consistent over the last decade or so.
Figure 5 shows planted acreage for some of the main almond varieties. Toward the middle of the series, one sees the large planted acreage for most varieties due to relatively high prices in 2004-05. Over time, acreage plantings have stabilized at lower levels. The increase in self-fertile almond acreage is noticeable in the mid 2010s. Operating cost savings from pollination and fewer equipment passes through the orchard were likely driving this trend (Champetier, Lee and Sumner, 2019). Price discounts for the Independence variety in comparison to nonpareil have stabilized, from as low as 2 to 4 percent discount in 2013-14, to on average of 11 percent over the last four years for Independence compared to nonpareil.
Closing Remarks
Overall, net returns from almond production have likely narrowed over the last decade due to increasing costs of production. Land values and interest rates have increased, increasing the costs of establishing an almond orchard. Pollination, irrigation and fertilizer costs have increased as a percentage of total operating costs, while almond prices have remained at relatively low levels over the last few years. The fact that acreage is still being planted suggests that the potential net returns remain relatively strong compared with other crops in California.
References:
Almond Board of California. 2019. “Almond Almanac 2019”
Champetier, A., H. Lee, and D.A. Sumner. 2019. “Are the Almond and Beekeeping Industries Gaining Independence?” Choices. Quarter 4.
Goodrich, B.K. 2019. “Contracting for Pollination Services: Overview and Emerging Issues.” Choices. Quarter 4.
Sumner, D.A., T. Hanon and W.A. Matthews. 2019. “Implication of Trade Policy Turmoil for Perennial Crops” Choices. Quarter 4. Available online:
University of California Agricultural Issues Center Sample Cost and Returns Studies. Available online: https://coststudies.ucdavis.edu/
Prolonged wet early season conditions have been linked to the “yellowing Krymsk” and “yellowing Rootpac-R” problem in young orchards. A yellowing ‘Monterey’ almond tree on ‘Rootpac-R’ rootstock in July of 2017. Similar yellowing symptoms have been
seen in some young Monterey on ‘Krymsk 86’ trees, particularly in wet springs. All photos courtesy of Luke Milliron.
One of the motivations for making good water management decisions early in the growing season is to reduce the risk of root and crown diseases that can eventually kill almond and other tree species. These diseases need three elements to infect and damage a tree: a susceptible host plant, a pathogen, and favorable environmental conditions.
A second motivation for diligent early season water management is that even in the absence of a pathogen like Phytophthora, root death due to waterlogging alone can damage or kill trees. Prolonged wet early season conditions have been linked to the “yellowing Krymsk” and “yellowing Rootpac-R” problem in young orchards. This problem which is most often associated with the ‘Monterey’ variety, often resolves itself with careful soil moisture monitoring. Similarly, in older orchards, over-watered conditions in March through May have been linked to the lower limb dieback (LLD) problem. Both conditions show that early season water management can greatly impact tree health much later in the season.
Possible lower limb dieback symptoms in July of 2019 in a mature orchard in Durham, CA. In older orchards, over-watered conditions in March through May have been linked to the lower limb dieback (LLD) problem.
Early season water management influences the environment where roots grow by affecting soil temperature and aeration and can be pivotal in how much tree decline occurs. Trees are expensive. The money and effort spent to establish them is lost, more costs lie ahead to replace them, and production is lost.
Choosing the Best Time to Start Irrigating
Each season you need to decide when to start irrigating. It can be difficult to choose the best time to start irrigation. There are a lot of different information sources you can use to make this decision. You can copy practices that you observe around you, evaluate soil moisture, consider the weather and evapotranspiration loss of the crop (ETc), or take a plant-based approach. Utilizing multiple information sources is highly recommended. However, utilizing the plant-based monitoring approach of stem water potential readings with a pressure chamber (or “pressure bomb”) has a distinct advantage over the others.
Schematic showing how water potential is measured in a severed leaf and stem (petiole) using a hand-held pump-up pressure chamber. Source: Adapted from Plant Moisture Stress (PMS) Instrument Company.
The pressure chamber directly determines the water status experienced by the trees, while the other sources, such as ET or soil moisture, although helpful, are indirect. The pressure chamber gauges the amount of positive gas pressure (in pressure units, e.g. bars) required to balance the level of water tension in a plant sample (e.g. leaf; see related graphic). The level of water tension in a leaf expresses the degree of effort utilized to pull water all the way through the tree from the soil.
Relying on an indirect information source, particularly an approach like beginning irrigation when your neighbor does, when the surface soil has dried out, or irrigating on the first hot day, could result in irrigating too soon.
Using Information to Delay the First Irrigation
Research in walnut orchards in California’s Tehama and Stanislaus counties has found that the start of irrigation can be delayed by waiting for mild to moderate water status when measured with the pressure chamber. Some observed benefits have been a minimum 10-percent reduction in energy for pumping, less tree stress during harvest season, and no impact on edible kernel yield. A managed (informed) delay in the start of irrigation may allow for deeper root activity late in the season. It’s possible that a strategy that starts the irrigation season too early promotes a shallow root system at the expense of deeper root development. This is completely contradictory to the conventional wisdom in walnut and almond production that early season irrigation allows for “banking of water” to help avoid high water stress at harvest. UC researchers plan to investigate this managed irrigation delay in almonds in the northern Sacramento Valley.
Before UC researchers begin to see results from this work in almonds, it is best to be cautious in choosing a level of stem water potential with the pressure chamber to trigger the first irrigation of the season. From everything we currently understand, waiting for a tree water status of -2 bars below the fully watered baseline before applying the first irrigation represents a low risk irrigation decision that could benefit long term tree and root health. To learn more about the pressure chamber, stem water potential, the fully watered baseline, and how to go about getting equipment and taking measurements, check out our series at: sacvalleyorchards.com/manuals/stem-water-potential/
Monitoring Weather—Crop Evapotranspiration (ETc)
If using the pressure chamber isn’t appealing, or a second source of information is desired, monitoring the weather and evapotranspiration crop losses is an option. This method is sometimes called a “water budget,” because it is analogous to budgeting money. Soil water storage in the crop root zone equates to a balance in a checking or savings account. ET equates to a debit from the account and significant rainfall or irrigation equates to a deposit or credit into the account. Water budgeting approximates the soil moisture level in the root zone rather than measuring it with soil moisture sensors.
Weekly ET reports are available during the irrigation season online or can be delivered weekly by email. ET is estimated based upon real-time weather measurements at regional CIMIS weather stations. Estimates are for trees with at least 50 percent canopy cover and need to be adjusted downward for smaller trees. Each report provides a real-time estimate of ET in inches for the past seven days, an estimate for the next seven days, and keeps a running total for the season. Accumulations begin at leaf-out for each crop which enables their use to help decide when to begin the irrigation season. It is important to know the hourly water application rate (inches/hour) of your irrigation system.
Using an example from the 2018 season, if we followed each weekly report from February 16 to May 3 for the Gerber South CIMIS weather station, it showed that cumulative ET for almonds was 7.51 inches while cumulative rainfall for the same period was 5.26 inches and resulted in a 2.25-inch soil moisture deficit. This assumed that all of the rainfall was effectively used in the orchard which is a site-specific consideration that needs to be adjusted accordingly in the water budget. Dividing this 2.25-inch soil moisture deficit by a water application rate of 0.07 inch per hour (i.e. an almond orchard with 124 trees per acre with one 16 gph microsprinkler per tree) equates to 32 hours of irrigation or the equivalent of two 16-hour irrigation sets that suit PG&E off-peak rates. Choice of set length is site-specific depending on irrigation system and soil type; however, it is best to minimize ponding conditions that can starve roots of oxygen and provide favorable disease conditions.
The previous example provides context on how this deficit relates to the irrigation system capacity. It is left to the irrigation manager’s judgement to continue to delay the beginning of irrigation to protect tree and root health, begin irrigation by partially refilling the soil moisture deficit (i.e. one 16-hour irrigation set), or begin irrigation and fully replace the soil moisture deficit. If this information were paired with the pressure chamber measurements and the stem water potential measurements were still within -2 bars of the fully irrigated baseline, the manager may have more peace of mind about continuing to delay the first irrigation.
Monitoring Soil Moisture Depletion
If neither the pressure chamber nor water budgeting appeal to you or you are looking for a supplement to one or both methods, directly monitoring soil moisture is an option. Checking soil moisture by hand is a very basic method to evaluate soil moisture conditions. There are many online stores where soil augers can be purchased (examples include: JMC Backsaver, AMS samplers, Forestry Suppliers, and Ben Meadows). For interpretation of soil moisture in collected samples, the USDA-National Resource Conservation Service also offers a nicely prepared publication with color pictures titled Estimate Soil Moisture by Feel and Appearance.
Stem water potential readings with a pressure chamber, evapotranspiration-based water budgets and soil moisture monitoring all bring different and valuable information to the decision of when to first irrigate almonds. Stem water potential readings with the pressure chamber offer the most direct measure of tree irrigation need. In addition, adopting this practice may both save water and encourage valuable deep root development. No matter if you choose to adopt one, or all three of these monitoring approaches, the irrigation-manager’s careful judgement is most important.
Air-assisted sprayers discharge tank mix as tiny spray droplets into an airstream that transports the droplets to the target tree or vine canopy. The mixture of air and spray droplets, known as the spray cloud, expands in both the vertical and horizontal dimensions as it moves away from the sprayer’s outlet. The speed of the air reduces drastically after exiting the sprayer and then continues to reduce gradually with distance away from the sprayer. Because the sprayer is moving, however, the spray cloud appears as having been bent backwards.
If we consider the continuous forward movement of the sprayer to be in short steps of equal lengths, we can determine the time the sprayer spends in each step by dividing the step length by the travel speed. We can then multiply the time by the flow rates of the air and spray liquid to know the volumes of air and spray discharged in each step movement. The volume of spray is what is applied in each forward step and the volume of air is how much is available to carry the applied spray. The slower the travel speed, the higher the volume discharged; the faster the travel speed, the lower the volume discharged.
During the spray application, immediate tree or vine canopies adjacent to the sprayer are the target canopies (Figure 1, below). Each tree or vine is bound by a ground area equal to row spacing times tree spacing. It is sufficient and most efficient for the air to carry spray droplets to the target, not beyond. This is because spray droplets carried beyond the target tend to either fall to the ground or potentially drift away by the wind when they miss canopies in the subsequent rows. However, the air speed and volume should be enough to cause the spray to penetrate the target canopy. This means that travel speed and air volume of the sprayer should be matched to the canopy size and density. Also, the number of nozzles used should not result in too much spray applied over and/or under the canopy. Effective spraying will result if the spray is strategically directed toward the target.
Figure 1. Basics of spray application
Sprayer Calibration: What, Why, When and How
What is it? Sprayer calibration is the adjustments made to a sprayer based on measurements taken to ensure that the correct amount of material (spray mix or active ingredient) is applied.
Why is it important? Calibration is best practice in pesticide spray application. When done correctly, it is a sure way to know how much material you would actually be applying to your crop. Incorrect calibration or not calibrating at all can result in inaccurate application rate, ineffective application, and illegal residues on the treated crop. Accurate calibration will lead to effective pest control while minimizing waste and negative environmental impact. Above all, accurate sprayer calibration will ensure compliance with the law as represented by the pesticide label.
When should it be done? Ideally, sprayer calibration should be done at the beginning of the growing season and whenever there is a significant change in conditions. Examples of changes in condition that may require calibration include: Change in ground condition (e.g. soil type, soil wetness, ground cover); change in target condition (e.g. crop type, canopy size, canopy density); change in spray material condition (e.g. density). Although not all the calibration steps may be necessary in response to a change, adjustments should be made to the components that are directly affected by the change. For instance, if only ground condition has changed, then only travel speed would have to be determined again and appropriate adjustments made. However, if a global positioning system (GPS) based speedometer device or mobile app is in use, then it may not be necessary to check speed again. This is because readings of GPS-based speedometers are not affected by changes in tire traction due to ground cover.
How should it be done? A major objective of sprayer calibration is the idea of optimizing the application. There are different ways to do it, but with the same or similar outcome. The steps could be as follow: 1) determine travel speed; 2) assess air profile to determine number of nozzles; 3) select nozzles; 4) measure sprayer output; 5) adjust sprayer output; and 6) assess spray coverage.
STEP 1: Determine Travel Speed
This should be done with the sprayer tank about half-full and the fan running.
Method 1 – Manual known distance method: Measure a known distance, D, (typically 100 or 200 feet) with a measuring tape in the orchard or vineyard where you would be spraying. Use marking flags to clearly indicate the distance. Using a stopwatch, measure the time, T, it takes for the sprayer to travel the marked distance at a preselected gear setting. Repeat this for at least three times in total and determine the average time. Calculate the speed, S, as:
When two people are available, in addition to the operator, person A should stand adjacent to the starting flag with one hand up (Figure 2a, below). Provide enough distance for the sprayer to attain the speed before reaching the starting flag. Once a predetermined feature on the tractor/sprayer (e.g. front of tractor/sprayer, center of front wheel, etc.) reaches the starting point, person A should lower the raised hand to indicate to person B to start measuring the time with a stopwatch. Once the predetermined feature on the tractor/sprayer reaches the ending flag, person B should stop measuring the time and then record the elapsed time on a clipboard.
Figure 2. Various ways to determine travel speed.
When only one person is available, in addition to the operator, fix the marking flags in the sprayer’s path (Figure 2b, above). Provide enough distance for the sprayer to attain the speed before reaching the starting flag. Once the front of the tractor touches the starting flag, start measuring the time with a stopwatch. Again, once the front of the tractor touches the ending flag, stop measuring the time and then record the elapsed time on a clipboard.
When only the operator is available, fix the marking flags in the sprayer’s path. Provide enough distance for the sprayer to attain the speed before reaching the starting flag. Maintaining sitting posture, start measuring the time with a stopwatch the moment the starting flag disappears and stop measuring just when the ending flag disappears. Record the elapsed time on a clipboard.
Method 2 – Manual tree passed method: Count about 10 or more trees or vines and fix two marking flags in an adjacent mid-row in the path of the sprayer (Figure 2c, above). Additionally, you can tie pieces of flagging tape on the vine adjacent to the marking flag to aid the operator’s visibility. Note the tree spacing, TS. Providing enough distance for the sprayer to attain speed before reaching the starting flag, measure the time it takes for the sprayer to travel the marked distance at a preselected gear setting. The number of trees passed by the sprayer, NT, is the count excluding the starting tree but including the ending tree. Repeat time measurement for a total of at least three times and determine the average. Calculate the speed as:
Method 3 – Automatic tracking method: Drive the sprayer for about 100 ft or more while observing the speed reading on a GPS device (a smartphone with a GPS speedometer app can be used for this). Repeat the observation for at least three times in total and determine the average. If the tractor pulling the sprayer is equipped with a GPS monitor, then speed measurement may not be necessary.
STEP 2: Assess Air Profile to Determine Number of Nozzles
Materials needed: Flagging tape, digital camera (e.g. smartphone).
Method:
Attach about 4 feet of flagging tape to each nozzle on the sprayer manifolds. Start the fan and observe the aloft flagging tapes from behind the sprayer, see Figure 3, below. Take a photo of the scene with a camera for reviewing. From the photo, determine the number of nozzles and their position that are well directed on the target canopy. Turn off nozzles that miss the target canopy. To better understand why this is necessary, see Figure 4, below.
Figure 3. To assess the air profile, attach about 4 feet of flagging tape to each nozzle on the sprayer manifolds. Start the fan and observe the aloft flagging tapes from behind the sprayer. (All photos courtesy of P. Larbi.)
Figure 4. Various nozzle configurations with different degrees of missing target canopy.
Also, attach a piece of flagging tape to the target tree or vine canopy and the next adjacent canopy in the path of the air. Drive the sprayer across the taped locations at the determined travel speed with the air running and observe the tapes on the canopies. If the tape on both canopies are sufficiently aloft, the air might be too much (Figure 5a, below). Adjust the air if the sprayer is equipped for that, considering the target canopy size and density. Otherwise, increase the travel speed to adjust the air (Figure 5b, below). Another option is to partially cover the fan inlet using a so called ‘Cornell doughnut’ (Figure 5c and 5d, below). Ideally, an automated means of adjusting the fan intake would be best.
Figure 5. A look at various ways of adjusting air volume.
STEP 3: Select Nozzles
Materials needed: Calculator, clipboard, nozzle catalog, nozzle selection mobile app
Method:
Knowing the desired application rate, AR, and row spacing, RS, determine the total sprayer output per side, SO, from all open nozzles as:
If the spray volume is intended to be uniform on each side, then divide SO by the determined number of nozzles to get the desired nozzle flow rate. Use this number to select the nozzle from a nozzle catalog.
However, SO can be split into different fractions for upper nozzles and lower nozzles. A common configuration for trees is 2/3 for upper nozzles and 1/3 for lower nozzles. Whatever the split ratio, the total should amount to the calculated SO. Various available software applications and mobile apps can be used to aid this determination.
STEP 4: Measure Sprayer Output
This should be done with the sprayer stationary. Alternate methods to that presented here exist.
Method:
With the sprayer running in a fixed position, confirm that the pressure gauge reading is accurate using a tool. Start spraying and collect spray water from each nozzle for 1 min using a measuring pitcher (see figure 6) and record the values in fluid ounces (oz). These should be the nozzles that will be used for the spray application. Calculate the flow rate of each nozzle as:
Repeat the measurement and determine the average.
Calculate the sprayer output by multiplying the average FR by N, for uniform application. For non-uniform application, do this separately for the upper and lower sections and sum them up.
Alternatively, you can automatically measure the flow rate by using a flow meter (e.g. SpotOn™ calibrator). Also, you can use a manifold patternator to observe uniformity of nozzle flow across all nozzles.
STEP 5: Adjust Sprayer Output
There are two adjustments that can be applied to the sprayer output in order to achieve the desired application rate, if the measure sprayer output is off. The first is adjusting the travel speed, while the second is adjusting the pressure.
Adjusting travel speed:
The adjusted travel speed, S2 can be obtained as:
where, AR1 = application rate obtained with the actual measured sprayer output in Step 4 AR2 = desired application rate in Step 3 S1 = travel speed measured in Step 1.
Adjusting operating pressure:
The adjusted operating, P2, can be obtained as:
STEP 6: Assess Spray Coverage
Attach water sensitive cards (yellow cards that turn blue when moist) to different locations
in the target canopy. Run the sprayer and apply water similar to the intended application. Evaluate the spray coverage to ensure that it is suitable. Make adjustments as necessary to obtain a suitable coverage.
Water sensitive card for spray coverage assessment
Once the proper settings have been obtained, maintain these settings in the actual application, making sure to factor in weather conditions. It is also important to clean the sprayer and maintain it in good working condition to ensure good performance.
A tree at the Yuba rootstock trial site that likely died of a bacterial canker infection sometime after leaf-out in 2018 (photo: Luke Milliron).
Roots are the unsung heroes of orchard plantings. They operate out of sight and are relatively difficult to examine and characterize. The roots of course anchor the trees to the soil and take up water and essential mineral elements. They also store carbohydrates and synthesize materials. Because roots play these key roles, rootstocks can influence scion vigor, growth and performance. Rootstocks vary in their tolerance to different soil types and conditions and their resistance to soil borne diseases and nematodes
As soil treatment options become increasingly limited, more restrictive and less effective, the priority to identify a genetic solution to solve or reduce the replant issue is of increasing interest. One genetic solution is to find or develop rootstocks to help manage soil related problems, such as soil borne fungi/bacteria, nematodes and soil acidity and excess salts. Of additional interest are root and tree characteristics imparting canopy size control, good anchorage and little or no root suckering.
The California prune industry has historically utilized just five rootstocks, Myrobalan 29C, Myrobalan seedling, Marianna 2624, Lovell peach and Marianna 40. The Prune Production Manual (UC ANR # 3507) has a very good chapter describing the traditional rootstock choices. You can find the production manual for sale at anrcatalog.ucanr.edu and as an e-version through Google Books. Recognizing the need for identifying additional rootstocks for California prune production, University of California farm advisors and campus-based faculty with funding from the California Prune Board designed and planted two replicated rootstock experiments in 2011 to evaluate 15 rootstocks for prune production. These rootstocks have diverse genetic backgrounds within the Prunus family (plum, peach, almond, etc.).
Replicated rootstock trials in growers’ orchards in Butte County and Yuba Counties allow UC researchers to evaluate a total of 15 rootstocks (Table 1, below) under very different soil, irrigation, and yield potential. The Butte plot is planted on Farwell clay adobe and the lighter textured Nord Loam soil types; this ground was previously planted to almonds on Lovell (peach) rootstock. In contrast, the Yuba site is planted on more typical prune ground (Kilga clay loam) and is prune following prune. The Butte site has tighter spacing at 12.5 feet in-row and 17 feet between rows (205 trees per acre), compared to 16 feet in-row and 18 feet between rows (151 trees per acre) at Yuba. The Butte plot is drip irrigated, while the Yuba plot has micro sprinklers. The differences in soil, crop history, tree density, irrigation, and resulting vigor at the two replicated trial sites allows for a rigorous evaluation of these rootstocks.
Tree Survival
Roger Duncan a pomology farm advisor based in Stanislaus County, who has done extensive trialing of rootstocks for almond production, has noted that rootstock choice is like an insurance policy. Although there is no perfect rootstock, careful rootstock selection can help guard against disaster. These two trial sites have illustrated an incredible range in rootstock survival, which helps illustrate a varying ability of these rootstocks to guard against disaster at two very different sites. Following a wet winter which delayed soil preparation in 2011, both the Butte and Yuba sites experienced extensive mortality and were significantly replanted in 2012. However, even after replanting in 2012, the rootstocks have experienced very different rates of survival.
Percent tree survival since the 2012 replanting was assessed at both sites in 2019 (Table 2, below). Survival ranged from 10 percent (Empyrean 2) to 97 percent (Atlas) at the Butte site, and 37 percent (HBOK 50) to 100 percent (Viking and Lovell) at the Yuba site. The two rootstocks that are only planted at a single site each have had dramatically different results, with the disastrous 10 percent survival of Empyrean 2 at Butte, compared to the 93 percent survival of Rootpac-R at Yuba.
Table 2: Percent tree survival at the Butte (September) and Yuba (June) sites in 2019. Values followed by the same letters are not significantly different at 95 percent using Tukey’s HSD. The numerically highest and lowest values are highlighted in each column.
There are other notable differences and similarities in survival between the two sites. Myrobalan 29C, Myrobalan seedling, and HBOK 50 have all had higher survival rates at the Butte site, potentially due to bacterial canker susceptibility at the Yuba location. At both sites, Atlas and Viking, which were planted in 2012 (not available in 2011), have had excellent survival (97 to 100 percent). Marianna 40 and Marianna 2624 have also had decent survival (80 to 87 percent). Finally, Marianna 30 has had very low survival at both sites (43 and 37 percent at Butte and Yuba, respectively).
Bacterial canker susceptibility has greatly colored the results at the Yuba location. Land with a history of the disease likely has ring nematode, and may also have sandy or low pH soils, low tree nitrogen status, or a clay/shallow hardpan. For land with a history of bacterial canker, having a prune orchard with a high rate of survival at maturity is no small feat.
The satellite image of this plot clearly shows several gaps of missing trees that are six trees in length (i.e. the number of trees in a rootstock treatment replicate, see related photo). Although there are several causes of tree loss in the plot, certain rootstocks have had very low survival in the same areas of the orchard where other rootstocks have 100-percent survival and vigorous growth. For example, Myroblan 29C an industry standard, had a mere 63-percent survival as of 2019, while Marianna 30 and HBOK 50 fared even worse, each at 37-percent survival. In contrast, Viking, Atlas, Krymsk 86, Lovell and Rootpac-R all had between 93- and 100-percent survival.
Vigor and Yield
The first mechanical harvest in the two trials was in 2017 and yield data continues to be taken. In addition to the Butte site having tighter spacing (205 trees/acre, compared to 151 at Yuba), the tree trunks have generally been larger, and yields per tree higher than Yuba. The 2017 yield results at Butte offer a valuable glimpse into the vigor of these rootstocks, since it was a very high yielding and unthinned crop, which helps illustrate the yield potential of these rootstocks. These high, unthinned yields were unsustainable and in 2018 there was poor return bloom at the site and low yields.
The 2017 harvest at the Butte site shows that a larger trunk, measured as trunk cross sectional area (cm2), generally higher dry yield (pounds per tree), and smaller fruit size (table 3). Among the smaller trunk size and lower yielding trees were Krymsk 1, HBOK 50, Marianna 58, Empyrean 2 and Citation. Among the largest and highest yielding were Myrobalan 29C, Atlas, Viking, Marianna 30 and Lovell. Similar yield and trunk size differences between rootstocks have been found subsequently at both sites. Of course, all rootstock trials that impose the same spacing across the plot disadvantage lower vigor rootstocks that could have been placed at a higher density.
Although there are similarities in yield performance of the rootstocks at both sites, there are some notable differences between sites. Rootpac-R, which isn’t planted at the Butte site, has had middle of the pack trunk size and yield at Yuba. Another notable difference is that Krymsk 86 is a fairly average vigor and yield rootstock at Butte but is among the largest and highest yielding at Yuba.
Table 3: 2016 trunk size (trunk cross sectional area in cm2) and ‘Improved French’ prune yield characteristics for the Butte County rootstock experiment harvested 8/29/17. Values are treatment means for the five replicates. Values followed by different letters are significantly different.
Anchorage & Suckering
In addition to survival and vigor (and resulting yield potential), there are other attributes that are important to growers. Anchorage is key since growers need trees to stand up on their own and not be blown over, as well as provide a straight up-and-down trunk for shaker harvesting. Degree of lean was measured with the level feature in the iPhone at both rootstock plots with one person pushing against the tree and another person measuring the deflection. Although rootstocks at the Yuba site had greater lean (there were notable wet soil conditions at the time of measurement), the rootstocks had similar relative lean to one-another at the two sites. Marianna 58 and Krymsk 1 had among the greatest angles of deflection, while Viking and especially Krymsk 86 showed little deflection at either site.
Removing suckers is a costly and cumbersome activity. In addition, rootstock suckers may offer a route for systemic herbicides to be taken up and damage the tree. Rootstocks suckers were rated on a one to five scale, with one being the fewest suckers and five being extensive and large suckers. Again, the two sites offered many similarities in rootstock performance. Myroblan seedling had the most rootstock suckers at both sites, while many rootstocks including Atlas, HBOK 50, Viking, Citation, Marianna 58, Lovell and Marianna 40 had few, if any suckers.
Rootstocks with Potential Problems
Many of the rootstocks haven’t performed well when survival, lean, and suckering were evaluated. Many of those same underperforming rootstocks also tend to be on the lower vigor and lower yielding end of the spectrum. Krymsk 1 and Marianna 58 had among the highest lean, and in-addition Krymsk 1 had low survival at Butte and was among the lowest yielding rootstocks. HBOK 50 also had high lean, poor survival at Yuba, and poor yield at Butte. Empyrean 2 which was only at Butte, had a mere 10-percent survival by 2019. Myroblan seedling had the worst suckering and had high lean at Yuba. The industry standard Myroblan 29C has performed well at Butte but has had low survival under the bacterial canker conditions in Yuba. Marianna 30, despite been among the highest yielding rootstocks per tree at Butte has had very low survival at both sites.
Rootstocks with Evident Strengths
Krymsk 86, Viking, and Atlas have all had very high survival at both rootstock trial sites. In addition, Krymsk 86 has been among the highest yielding at Yuba, and Atlas and Viking have been high yielding at both sites. Krymsk 86 has maintained its reputation for excellent anchorage, while Viking also showed little lean at both sites. Finally, both Viking and Atlas had a sucker rating of zero at both rootstock plots.
Where is Rootstock Selection in the Industry Headed?
Atlas, Viking, and Krymsk 86 have all shined at these two rootstock plots. Krymsk 86 is the only one of these that is so far seeing significant adoption in the prune industry. Following widespread adoption of Krymsk 86 in the Sacramento Valley for almond production, Krymsk 86, known for its superior anchorage and tolerance to wet feet, has been planted now in many new prune orchards. Like the higher vigor at the Yuba site and in contrast to the middling vigor at Butte, we have heard from growers that Krymsk 86 has been a high vigor rootstock in their plantings. Just as with growing almonds on Krymsk 86, growers should test for and be wary of planting Krymsk 86 where nematodes, particularly root-knot, are present.
As described in an article in the September/October issue of Progressive Crop Consultant (progressivecrop.com/2019/10/californias-prune-orchard-of-the-future) choosing a higher vigor rootstock and/or planting at a tighter spacing leads to capturing more sunlight and having a higher yield potential. However, when hand pruning large prune trees can cost $1,000 per acre, many growers are adopting mechanical hedging, and some progressive growers have had an increased interest in low vigor rootstocks. A couple of these growers have begun trialing low vigor inducing rootstocks in high density plantings, in hopes that low vigor rootstocks will reduce pruning expenses. Low vigor, high density and potentially trellised plantings, stand in stark contrast to the vigorous rootstocks that have stood out in these two trials. The choice between high and low vigor rootstock may prove to be one of the key defining choices where the California prune industry heads in the coming years.
We want to sincerely thank an amazing team of UC researchers, as well as support from dryer managers at Sunsweet Growers Inc. This work is made possible by the generous funding support of the California Prune Board.
. Strawberry fruit are very susceptible to gray mold caused by Botrytis.
Introduction and Significance
When evaluating the impact and importance of a plant pathogen, one could consult various metrics to make such an assessment. One could consider the values of the affected crops, the acreages planted, the geographic distribution (how widespread is it?) of the pathogen, the mode of pathogen attack (does it affect leaves, flowers, both?), the persistence and staying-power of the organism, and the difficulty in controlling the pathogen. The Botrytis fungus, causal agent of gray mold and other related diseases, is one of the few plant pathogens that could arguably be placed at or near the top of a key pathogen list based on all of these criteria. Field professionals likely are familiar with the challenges of gray mold for the crops they oversee. However, what may be overlooked is the impact of Botrytis throughout a broad spectrum of many agricultural commodities and settings. Botrytis is an unusually dangerous threat due to its ability to infect dozens of crops, uncommon versatility as a microorganism, and propensity to change genetically in adapting to fungicide chemistry.
Table 1. Examples of Vegetative, Flower, and Fruit diseases caused by Botrytis on diverse crops. *In contrast to most other crops diseases on onion are not primarily caused by Botrytis cinerea but by other Botrytis species.
Broad Spectrum Impact on Crops Worldwide
Botrytis is a highly ranked plant pathogen due to its broad host range that includes hundreds of plants. Such hosts are in almost all commodity groups: annuals and perennials, herbaceous and woody plants, food and ornamental crops, vegetable and fruit and field crops. Included within this diverse list are dozens of high value vegetable, fruit, and ornamental commodities (examples are listed in Table 1 and seen in Photos 1 to 4), for which gray mold can inflict sizeable economic losses. This broad spectrum of activity can also be described based on the type of plant tissue affected. Depending on the crop host, Botrytis can infect the vegetative portions (stems, petioles, leaves), flowering parts (buds, sepals, petals, reproductive tissues), and fruit (immature and ripe phases).
The Botrytis impact on all these crops and commodity groups is further compounded by two factors. First, the gray mold fungus can cause significant disease both before and after harvest. Pre-harvest disease occurs when Botrytis is active on developing plants in the field and greenhouse, resulting in blight, decay, and rot that reduces crop quality and harvestability. In addition, for many crops the Botrytis fungus can be a contaminant on or even inside the harvested plant commodity. Once these contaminated commodities are stored, the Botrytis fungus can become activated under certain postharvest conditions and cause rots and decay in storage (Photo 5). Secondly, we note that Botrytis is found throughout most agricultural and horticultural production regions in the world. In the USA, there are only a few states where an official report of Botrytis is lacking. Likewise, Botrytis is found throughout the world and is reported to cause disease on a huge number of crops and plants.
On pea, Botrytis can cause a pre-harvest disease but is perhaps more important as a postharvest problem, as seen by these lesions on stored pea pods.
Versatility as a Microorganism
A notable feature about Botrytis is the organism’s ability to function in different modes or survival strategies. This diversity of biological activity is not commonly seen in plant pathogens and points to the extreme versatility of Botrytis as a microorganism. Pathogen: We are most aware of Botrytis as an aggressive, difficult to control primary pathogen of plants. From an agricultural point of view, this is the most prominent role for Botrytis. Saprophyte: In a different mode, Botrytis does not even need a living plant. As a saprophyte, the gray mold fungus can grow, thrive, and reproduce on senescent, dying, and dead organic plant tissue. Spores that land on decaying matter can readily germinate and colonize such substrates. Secondary invader: If a plant is injured from weather extremes, damaged from mishaps in the field, or has symptoms caused by other pathogens, spores of Botrytis can drop onto such compromised plant tissues and aggressively grow on and overwhelm the injured plant. In such situations Botrytis did not initially cause the problem but is a secondary invader that can make the overall problem worse.
Dormant sleeper: Botrytis can be a sneaky adversary. This pathogen can infect and penetrate plant tissues but remain dormant within the protection of its host. Later, when the conditions change, the weather warms, or the plant tissues mature and grow, the once dormant Botrytis wakes up and begins to colonize the host, resulting in gray mold disease. Such dormant infections are called latent or “quiescent” infections. Opportunist: Botrytis is an opportunist because it can switch from being a harmless saprophyte, growing on dead tissue that growers do not care about, to an aggressive pathogen causing problems. Numerous examples exist of this switching. The Botrytis starts by colonizing dead parts of plants, such as old flower parts; if these Botrytis-laden dead pieces are in contact with healthy tissue, the Botrytis is able to bridge over from the dead to the living, resulting in a primary disease problem (Photo 6).
Gray mold is also versatile in how it survives and is moved around in the agricultural environment. Airborne spores: The gray color of the fungus, as it appears on infected plants, indicates Botrytis is producing millions of spores. These spore masses (Photo 7) are readily spread long distances by winds, splashing water, and physical contact. Sclerotia: Under certain conditions Botrytis can produce a survival structure, the sclerotium, which is a hard, black, oblong to spherical structure that can be up to ½ inch long. Sclerotia can withstand dry, warm, or cold conditions and can survive inside dead crop debris or buried in the soil; under conducive conditions these sclerotia can germinate and produce mycelium that infects the host. Sclerotia can form within the hollow stems of plant hosts and be carried with the plant if these stems are moved to other locations. Sclerotia can become mixed in with seed and become a seedborne contaminant. Embedded mycelium: In another survival mode, the hyphal strands of Botrytis can penetrate and be buried inside the living flowers, buds, or stems of plant hosts. This strategy allows the gray mold fungus to be protected from harsh environmental conditions, giving it an opportunity to wait for more favorable situations.
Botrytis can cause a brown decay on orange fruit by first colonizing dead flower parts that stick to the fruit; here the old blossom has been moved aside to show the developing brown lesion.
Genetic Plasticity and Loss of Fungicide Efficacy
Botrytis is notorious for becoming resistant (insensitive) to fungicides because of its high genetic variability and adaptability, profuse production of spores, and multiple cycles of spore production. Molecular recombination, mixing of genes between strains, and mutations provide the raw genetic material for resistance to develop. When fungicides are applied numerous times to a susceptible crop, the presence of the chemical challenges Botrytis and can result in the selection of individual strains that are no longer affected by that chemistry. Fungicides with single-site modes of action are especially at risk for inducing resistance in Botrytis. Worldwide, resistant isolates of Botrytis have been confirmed for all of the single-site fungicide categories used to manage gray mold (Table 2). Even more alarming are the research findings that show individual isolates of Botrytis can possess resistance to multiple fungicide classes; there are even isolates that are shown to be resistant to seven different fungicides, each of which has a different mode of action.
Table 2. Fungicide classes for use against Botrytis and for which resistance has been reported. *FRAC = Fungicide Resistance Action Committee
A Note About Botrytis Species
This article is addressing the broad topic of gray mold caused by Botrytis, and for most crops the pathogen species is Botrytis cinerea. However, examining the DNA of Botrytis from different crops in different parts of the world, powerful molecular tools and innovative techniques are detecting multiple, diverse genetic signatures which indicate that B. cinerea is not the only gray mold species out there. For example, a series of studies documents that strawberry can be infected by one or more of the following Botrytis species: B. cinerea, B. fragariae, B. caroliniana, B. mali, B. pseudocinerea. Such findings can have implications for the farmer and the field. On grapes in France, for example, the B. pseudocinerea species is more active in the early spring, while B. cinerea is active in both spring and fall. There are indications that a higher percentage of B. pseudocinerea isolates are resistant to some fungicides than B. cinerea isolates. So in the future it might be critical to know exactly which species is causing gray mold, since different species may require slightly different management approaches.
Management of Gray Mold
Controlling gray mold diseases requires the implementation of IPM practices. Fungicides: Judicious and strategic use of fungicides remains the primary means of managing gray mold. Multiple applications usually are needed, throughout the season, using diverse products having different modes of action. Fungicides with single-site modes of action are especially at risk for inducing resistance in Botrytis, so multi-site products should be integrated into spray programs. Sanitation: Sanitation measures, such as the removal of dead leaves and diseased fruit, appear to only slightly decrease gray mold incidence and cannot replace reliance on fungicide programs. Given the logistical difficulty and expense of such measures, these sanitation steps are not practical for most commercial growers but could be a consideration in certain circumstances, such as for greenhouse crop production.
Botrytis produces masses of airborne spores that readily land on host crops.
Modifying the environment: Because Botrytis is dependent on free moisture and high humidity, reducing such factors can help reduce disease severity. The venting out of moist air in a greenhouse is one example of such environmental modifications. Use of drip irrigation is a field equivalent of reducing water on foliage and can reduce gray mold severity. Canopy modification (pruning to remove leaves and laterals and increase air flow and light penetration) can help with bunch rot control in grapes. Resistant or tolerant cultivars: For most crops there are no cultivars that are genetically resistant to Botrytis. However, some cultivars may experience less gray mold for other reasons. For example, some strawberry cultivars suffer less gray mold due to the upright growth habit of leaves and flowers. Use such cultivars if available. Reduce damage: Reducing damage to crops in the field will reduce the opportunities for Botrytis to invade as a secondary decay organism. Proper harvesting and postharvest handling of fruit are critical to reducing fruit injury and lowering the impact from gray mold. Storing fruit at low temperatures is also necessary to retard gray mold and slow down the aging and senescing of fruit.
The funded amount for this project from CCGGA is devoted to support travel to California for Dr. Ulloa and to assist in evaluation, progeny development, breeding and coordination of seed increases of selected developed progeny and breeding lines of Pima and Upland cotton for future testing and germplasm public releases with improved resistance/tolerance to Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4), a soil borne fungal pathogen. These FOV4 breeding research efforts and activities are coordinated and supported by the California team. In addition, funding partially pays for professional research/services support needed to increase our understanding of plant FOV4 defense mechanisms.
Over the past 14 years, the fungus that causes FOV4 has impacted fields in California’s San Joaquin Valley. This fungus is particularly difficult to control in cotton as the hyphae or fungus- overwintering structures reside in the woody vascular tissues, preventing the penetration of fungicides. These structures can survive in soils indefinitely. In the United States, FOV4 was first confirmed in California cotton fields in 2003, however, in 2017 it was also identified in far-west Texas and in 2019 in New Mexico.
Cultivars with relatively high levels of resistance to FOV4 were originally identified in commercial Pima cotton (Gossypium barbadense L.), ‘Phytogen 800’, and originated-pool germplasm, ‘Pima S-6’. Field evaluation of cotton cultivars in FOV4-infested fields have provided information to develop a number of generalizations: (1) most Pima cultivars show more severe symptoms and suffer higher levels of stunting and plant mortality from FOV4 than with most Upland and Acala cottons; (2) some moderate to highly-resistant commercial Pima cultivars have been developed from several seed companies and private breeders; and (3) several USDA-ARS 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). These germplasm lines have helped to increase the genetic base for FOV4 resistance in Pima Cotton. Typical FOV4 symptoms are shown in Figure 1. Disease symptoms of this pathogen have been observed to differ between Pima and Upland cotton.
Figure 1. Foliar and root symptoms of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4). A) Foliar symptoms for Pima (Gossypium barbadense L.) cotton and B) Foliar with no visual symptoms and root with vascular root staining symptoms for Upland (G. hirsutum L.) cotton. (All photos courtesy of M. Ulloa.)
From 2006-18, we have been evaluating Pima germplasm from the USDA ARS and international breeding collections, and Upland germplasm from the USDA ARS Cotton Germplasm Collection College Station, Texas or breeding lines from around 13 public (universities and USDA) cotton breeding programs across the Belt through the regional breeder testing network or RBTN sponsored by Cotton Inc. and have provided information about the level of FOV4 tolerance of these breeding lines and germplasm. In addition, 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.
During the growing season, plant responses to fungus-inoculum pressure were assessed through evaluations of root and stem vascular staining levels, plant mortality, foliar wilt symptoms and measures of relative plant vigor. In Upland cotton, germplasm with good levels of tolerance have been identified, and new breeding lines are being developed by USDA-ARS and the University of California. After FOV4 artificial-greenhouse and natural-infested FOV4 evaluations of these accessions, less than 0.1% were selected to develop highly resistant FOV4 progeny. Two sources (NM12Y1004 – NM12Y1005 and SA-3208) of Asiatic breeding origin were identified with tolerance to FOV4 and used to introgress and increase resistance. Pedigree information from additional parental lines or breeding stocks used to develop progeny revealed their sources to be exotic and wild Upland germplasm – triple/multiple crosses, deriving these SA-obsolete cultivars named ‘Auburn M’, ‘DES 920’, ‘MARSPD202085’, ‘S.N.0503-1’, PD 2165, and ‘Stoneville 14’, among others.
In 2019, around 130 selected breeding lines were ginned, acid delinted, and planted at two infested field sites in California [Los Palos (Figure 2) and Tipton Co. (Figure 3)] to validate their resistance/tolerance against FOV4.
Figure 2. Infested Fusarium wilt race 4 (FOV4) field site around Dos Palos, CA. planted with selected breeding lines to validate their tolerance level before public releases. Photos showing Dr. Ulloa next to one of the FOV4 highly resistant Upland lines surrounded by empty research plots from a susceptible FOV4 variety-check.
These selected lines were also planted at the Tipton FOV4 infested site (Figure 3). In addition, evaluations were performed on more than 500 additional Pima and Upland cotton lines from progeny and breeding lines with different levels of FOV4 tolerance/resistance. Most of these lines were derived from multi-cross-combinations between and within Pima and Upland cultivars or germplasm lines with known FOV4 resistance to develop progeny and new populations to assess FOV4 resistance.
Figure 3. Infested Fusarium wilt race 4 (FOV4) field site around Tipton, CA. planted with selected breeding lines to validate their FOV4 resistance/tolerance level before public releases, with an additional 500 Pima and Upland entries. Photos showing evaluation site and roots with no vascular root staining, a typical diagnostic infection sign of FOV4.
In addition, a subset of these entries was also planted in the El Paso, TX area in FOV4 infested field (Figure 4). Following are images from the FOV4 infested field site near El Paso, TX. We planted lines with known levels of FOV4 tolerance, and resistant and susceptible FOV4 check-cultivars using a RCBD with three replications (Figures 1-3).
Continuing with the breeding efforts of this cooperative project next year, we anticipate additional visits to California by Dr. Ulloa to coordinate and support the selection, harvest, ginning of breeding lines with good to excellent FOV4 tolerance/resistance for the 2020 year’s season.
Figure 4. Infested Fusarium wilt race 4 (FOV4) field site around El Paso, TX area planted with selected breeding lines to validate their tolerance level before public releases.
