California Ag Network

Tag: UCCE

  • UCCE Carrot Production and Pest Management Webinar, Oct. 9

    As part of the UC Ag Experts Talk webinar series, Dr. Jaspreet K. Sidhu, Vegetable Crops Farm Advisor with the University of California Cooperative Extension, Kern County, will lead the next webinar on October 9, 2024 (3 – 4 p.m.).  She will discuss carrot production in California’s Central Valley, the biggest producer in the U.S. Dr. Sidhu will include major pest challenges and pest management with research findings for management especially for root knot nematodes, Alternaria leaf blight and cavity spot. One DPR CE unit (other) and one CCA CE unit (IPM) are pending. In order to qualify for credit, a final exam will be given and must be passed with a 70% or higher. Register to attend this free webinar HERE.

  • Former Kern County Viticulture Farm Advisor Passes

    Donald A. Luvisi, UC Cooperative Extension viticulture advisor emeritus of Kern County, passed away in Bakersfield on July 10 at the age of 87.

    Luvisi served as the viticulture farm advisor for Kern County from 1960 until his retirement 39 years later in 1999. He was widely recognized as a pioneer of the modern-day California table grape industry and his research influenced a significant expansion in the production of varieties such as ‘Flame Seedless,’ ‘Redglobe’ and ‘Crimson Seedless,’ along with improvements in fruit quality associated with his work with gibberellin, ethephon and girdling.

    “He gave table grape growers the knowledge they needed to maximize packable yields by investigating and extending the nuanced production practices specific for each variety,” said Rhonda J. Smith, UCCE viticulture farm advisor emeritus.

    Luvisi was widely regarded as an expert in postharvest handling of table grapes due to the impacts of his work on sulfur dioxide (SO2) fumigation. SO2 is used to inhibit the growth of fungi that can break down fruit in storage. In 1987, SO2 was removed from the ‘Generally Regarded As Safe’ (GRAS) listing by the U.S. Food and Drug Administration (FDA), and as a result, residue data and new application patterns had to be developed to prevent grapes from decaying in storage. Luvisi responded through his participation in more than 20 experiments annually that led to the acceptance of the “Total Utilization Fumigation” method and conversion of much of the industry to it from traditional fumigation. The restoration of newly approved postharvest SO2 fumigation methods was estimated to prevent 40%-50% losses in table grape production that at the time was valued at $200 million to $250 million.

    The last decade of Luvisi’s career was focused on the evaluation of rootstocks for table grape production. These rootstocks were developed as a response to growers reporting replant problems in second- and third-generation vineyards due to the buildup of plant-parasitic nematodes in the soil. He conducted more than a dozen decade-long trials evaluating the performance of common table grape varieties on these rootstocks that led to guidelines for their use by local growers. The use of soil-borne pest resistant rootstocks has become an industry standard practice within the California table grape industry.

    “Don was an internationally respected viticulturist, with particularly broad knowledge of table grape and wine production,” said Matthew Fidelibus,UCCE viticulture specialist. “He was also a generous and beloved colleague.”

    Don Luvisi was not only an internationally respected viticulturist, “he was also a generous and beloved colleague,” said Matt Fidelibus, shown on left with Luvisi.

    After retiring in 1999, Luvisi split his time between Bakersfield and Calistoga, where he managed a family vineyard. When in Bakersfield, he was generous with his time as a mentor to three subsequent UCCE Kern County viticulture advisors, and frequently met with his friends within the table grape industry.

    In the early 2000s, he was highly influential in the development of the ‘General Beale Pilot Project’ that developed and tested area-wide management programs to control the glassy-winged sharpshooter, a vector of the potentially devastating Pierce’s disease of grapevines. His knowledge of the grape industry, combined with the personal relationships he had developed over a lifetime, proved invaluable in establishing this highly successful project that remains effective today.

    Following his passing, former UCCE viticulture advisor Jennifer Hashim-Maguire said, “I’m forever grateful for having Don as a mentor and friend. His early tutelage at Cooperative Extension sowed the seeds of a career in table grape production that now spans decades and several countries.

    “Luvisi’s passion for the advancement of the grape industry was contagious and unsurpassed. As a (wine) grower himself, he understood firsthand the challenges of farming and was eager and generous to share technical information and solutions with growers all over the world.

    “Don’s legacy is measured not just in past research conducted and the growers he helped throughout his life, but in his kindness and the numerous relationships he cultivated in the industry from California to Australia, Chile to Greece and numerous places in-between,”Hashim-Maguire said. “The global table grape industry is an interconnected extended family and I know that I’m only one of many who will miss him deeply.”

    Luvisi was an “exceptional mentor,” said Stephen Vasquez. From left, Allison Ferry-Albee, Ashraf El-kereamy, Luvisi and Vasquez.

    Stephen Vasquez, a former UCCE viticulture advisor who served in Fresno County for 14 years, described Luvisi as an “exceptional mentor” who was always generous with his time and freely shared his knowledge, leaving a lasting impression on Vasquez who was a young viticulture plant pathologist in 1999.

    “As a UC Davis plant pathology grad student working on grape diseases, Don would drive me around Kern County and show me areas with high incidences of grape diseases. We’d look at powdery mildew, measles, bunch and sour rots, etc. and talk about why they were problems in the vineyards we visited. The next time I was in town, Don would drive me around new vineyards and test my knowledge. Often, I would be stumped, and he’d explain the subtleties of the diseases. This scenario lasted for two summers, and I was grateful for the experience.

    After completing his master’s degree, Vasquez applied for a viticulture farm advisor position in Fresno County. Luvisi was on the hiring committee along with several other viticulture farm advisors. “I was prepared to be grilled. Instead, he questioned me on grapevine disease scenarios with slight twists, which I had been trained to solve the past two summers. Don’s plan wasn’t to prepare me to be a farm advisor, he saw an opportunity to share his knowledge with someone who was interested in learning,” said Vasquez, who is now executive director of the Administrative Committee for Pistachios and looks for opportunities to share his knowledge with early career scientists.

    Funeral services for Luvisi were held at St. Francis Church in Bakersfield on July 30 and burial on Aug. 1 at the Holy Cross Catholic Cemetery in St. Helena.

    Those wishing to honor Luvisi’s life through contributions are encouraged to donate to the Don and Mickie Luvisi Agriculture Scholarship at Calistoga Junior/Senior High School. Donations to the scholarship fund can be made online at this link: https://www.convergepay.com/hosted-payments/?ssl_txn_auth_token=rc5FKo1YQV%2Bt0Vk%2F%2F5PGSQAAAY2E3mHg#!/payment-method. At checkout, specify “Scholarship” in the “Select Donation” field, then type in “Luvisi Scholarship” in the “Description” field.

    Checks can be made to Calistoga Joint Unified School District with “Luvisi Scholarship Fund” in the memo line. Those can be mailed to 1520 Lake Street, Calistoga, CA 94515. For more information, please contact Carla Surber at csurber@calistogajusd.org. — By David Haviland & Pam Kan-Rice (UCANR)

  • Managing Aphids in California Prune Orchards

    By Sudan Gyawaly, UCCE Northern Sacramento Valley IPM Advisor — ‘Leaf curl plum aphid’ and ‘mealy plum aphid’ are the key pests of prune orchards in the northern Sacramento Valley. Both aphid species survive the winter in the orchard at egg stage near the base of buds. Once hatched, around bloom time, they vigorously feed on the young foliage and build up their population quickly. From May (leaf curl plum aphid) and June/July (mealy plum aphid), most aphids leave the prune trees and feed on alternate weed hosts outside the orchard.

    Mealy plum aphid

    Both aphid species infest growing leaves and stems in spring and summer, which can cause curling and stunting of the leaves. Serious aphid infestation can reduce tree growth, vigor, and potentially reduce fruit sugar content. Accumulation of honeydew, which these aphids excrete while feeding, results in the development of sooty mold which can potentially lead to fruit cracking.

    Damage caused by plum leaf curl aphid, Jack Kelly Clark, UC IPM

    Determining the need to spray for aphids and optimum spray timing.

    The decision to spray for aphids depends on the past and present orchard aphid pressure, which also helps determine the optimum spray timing. Also, the need to spray for other prune pests (such as scale or peach twig borer) can influence the selection of materials and application timings for aphids. Several pesticide options are available for aphid control for different application timings (see table, below). An effective aphid management program should always weigh the relative cost, efficacy, and impacts on natural enemies and surface water quality.

    If aphids are a consistent problem in an orchard, a late fall/early dormancy (Nov-early Dec) spray with a low label rate of a pyrethroid insecticide provides good control of aphids. Low label rates of these insecticides applied at this time are effective, yet the risk of surface water runoff is reduced. Oil spray during this period can seriously impact parasites (natural enemies) and is not recommended, especially if leaves are still on trees.

    Dormant sprays (late Dec-Jan) of pyrethroid or pyrethroid plus oil treatments are effective against aphids and other pests, such as scale and PTB. However, this application timing poses higher risks of surface water contamination.

    If a fall/dormant spray is not applied, dormant spur sampling can help decide the need for aphid sprays at bloom. Dormant spur sampling for aphids involves sampling for aphid eggs, and the treatment threshold for aphids is just 1 egg out of 100 spurs. However, aphid eggs can be hard to find on dormant spurs, and not finding eggs on spurs doesn’t mean none are present. Therefore, a spring/summer monitoring is necessary to complement the dormant spur sampling if no eggs were found on dormant spurs. Bloom time sprays of narrow-range oil are effective against aphids.

    If aphids are only an occasional problem in the orchard and sprays were not applied at fall/dormant or bloom time, the need to spray for aphids is based on spring/summer monitoring. Spring/summer aphid monitoring involves weekly monitoring (from petal fall until a treatment is applied or July 15) of 40 trees/block for aphid infestation and determining if those trees have significant (aphid covering >10% of tree leaf surface) aphid infestations. Treatment is warranted if a threshold (12 out of 40 trees monitored in a block) have significant aphid infestation. Click this link for details on spring/summer monitoring.

    The table below (adopted from Franz Niederholzer) provides a good summary of various prune aphid control materials, their application timings, efficacy against key prune pest and risks to water quality.

    Label is the law. Always read the label of the product being used.

    Disclaimer: Products listed in this table do not constitute a recommendation, and many of the active ingredients presented in this article can be purchased under multiple trade names.

  • New Herbicides Tools for California Rice Weed Management in 2024

    This year brings several new chemical tools to California rice. With many herbicide-resistant species as well as emerging problematic weed species, the new chemistries are a welcome tool for managing resistance and preventing the selection of resistant biotypes.

    Rice (photo credit: Brad Hooker)

    Last year, we had use of Loyant® CA Rinskor™ active (florpyrauxifen-benzyl) for the full season (registered late in 2022). Loyant®, which is an auxin mimic, is applied as a foliar product. It gives additional options for early-season control of sedges and broadleaf weeds, and although not strong on watergrasses when applied alone, provides added control when tank-mixed with other herbicides for grass control. Based on data collected in 2022-2023, two good tank-mix options for watergrass control are SuperWham®/Stam® (propanil) and Regiment (bispyribac-sodium). It does not control sprangletop.

    Cliffhanger™ (benzobicyclon) was just registered in 2024, and is a new formulation of a previously-registered granular product already widely in use in California rice. Since it can be applied as a foliar product, it expands the timing that benzobicyclon can be applied in the flooded system. It can also be applied as a direct-stream application into the water. It is an HPPD-inhibitor, providing a good option for rotation. It controls sprangletop, ricefield bulrush and smallflower umbrella sedge. Additional tank-mix testing will be occurring this season to determine if it might be a good partner in combination with other herbicides for added late-season watergrass control.

    The last product recently registered is Zembu™ (pyraclonil). Zembu™ is a granular formulation of pyraclonil, applied pre-emergence or at day-of-seeding into a flooded field. It provides control of smallflower umbrella sedge and broadleaf weeds, and provides suppression of watergrass. As a PPO-inhibitor, it is a new mode of action for watergrass, as the only other PPO-inhibitor registered in California rice only has activity on sedges. It will provide a great rotational option for growers at the beginning of the season, as well as a great partner product (for added control) with other granular into-the-water products.

    As always, the label is the law, so make sure to read and follow the current labels for each of these herbicides (found on the manufacturers website or at the Department of Pesticide Regulation’s website). Also check in locally with your Agricultural Commissioner’s office for training information and any other county-specific requirements.

    With these three new options, as well as the currently-registered products, rice growers in California should have a great suite of tools available this year, both for resistance management as well as to prevent the selection of future resistance. For help planning a weed management program, please reach out to your local Rice Farm Advisor. — By Whitney B Brim-Deforest, UCCE Rice Advisor

  • UCCE Tulare County Assists Pathologists in Survey for Decay Fungus in Prunes

    Recently, extensive wood decay-related limb breakages have been reported in commercial prune orchards in the Sacramento Valley, adversely affecting fruit production and limiting the value of salable firewood upon orchard removal. Several fungal genera such as Phellinus, Rhodoformes, Schizophyllum, Sterum, Trametes, Ceriporia, and Perenoporia have been recognized for wood-decaying activity on California prunes.  Phellinus pomaceus has been the primary organism associated with prune decay symptoms in the Sacramento Valley; however, it is yet unknown whether P. pomaceus is present in southern San Joaquin Valley prune orchards.

    Figure 1: Symptoms of advanced Phellinus pomaceus infection, showing white rot internal decay of heartwood. Scale bars 10 cm.

    Phellinus pomaceus, specific to prunes and other plums, is one of the commonly reported wood-decaying fungi that attack the heartwood (non-functional xylem) of mature trees (Figure 1). It tends to attack the trunk and large-diameter branches, often resulting in broken limbs and the loss of fruit-bearing scaffolds. In fact, older trees are more likely to contain infection by the fungus, and frequent pruning of large branches may increase the probability of infection due to exposure of the internal heartwood. The fungus can be identified based on its fruiting bodies that emerge as conks or shelf-like brackets that are usually hard, woody, and hoof-shaped (Figure 2). Under the right conditions, these fruiting bodies are often perennial and may exhibit a darkened upper surface after several years of development.

    UCCE Tulare County assisted UC Davis researchers from the Department of Plant Pathology in surveying Tulare County prune orchards for presence of P. pomaceus. Laurel Hoffman, a PhD student working under Dave Rizzo, Professor of Plant Pathology, visited our local UCCE Tulare County office, coordinating with Elizabeth Fichtner, UCCE farm advisor, to visit and survey prune orchards for the pathogen. With the assistance of Walter Martinez, Tulare County Ag Technician, and Santosh Bhandari, Assistant Specialist, six local ‘French’ prune orchards were surveyed with data collected on tree canopy status and presence or absence of fruiting bodies associated with decay fungi. Surveyed orchards were all over 15 years old and were in varying states of overall productivity. Samples from putative decay fungi were collected and brought back to UC Davis for genetic sequencing to identify the specimens. A preliminary observation based on the initial survey suggests that the prevalence of putative decay fungi in prune orchards is lower in the southern San Joaquin Valley than in the Sacramento Valley. The presence of P. pomaceus in the southern San Joaquin Valley has not yet been confirmed.

    To date, there are no control measures for management of P. pomaceus. Chemical control strategies are not available for management of this disease. Removal of fruiting bodies may limit sporulation, thus having the potential to slow disease transmission. However, the value of this technique is limited by the ability to remove conks prior to sporulation and conks may be difficult to see, particularly after leaf out. Additionally, if the pathogen is present at a high level in (or near) affected orchards, the removal of conks may not significantly influence the total load of spores at a site. Fruiting body removal would not affect the health of infected trees because they are already colonized by the fungus.

    Most of California’s prunes are sold in the dried fruit market; however, a few orchards are reserved for fresh prune production. After the economic lifespan of prune orchards, trees are removed, generating wood that can either be sold as firewood, or reintroduced to the soil through whole orchard recycling.  Infection with decay fungi such as P. pomaceous may adversely affect fruit production, limit the lifespan of infected trees, and reduce the economic longevity of orchards. — By Santosh Bhandari, Laurel Hoffman & Elizabeth Fichtner, UC Cooperative Extension

  • Efficacy of a Hull Split Spray vs. Sanitation for NOW Control

    Navel orangeworm (NOW) is most effectively controlled with the cultural practice of winter sanitation. Winter shaking almond trees to remove mummy nuts has proven to decrease next year’s NOW damage better than any other approach. The reason for this is clear. NOW overwinters as larvae in mummy nuts left in the tree after harvest and it is in these nuts the population carries over into the next season. Adult moths emerge in spring, mate, and lay eggs on mummies that are still in the trees as the females can’t find the new crop nuts until hull split. The second generation will then put direct pressure on the new crop nuts at hull split and the third generation will chew the nuts up during the harvest period.

    The way almond prices have been going recently, there’s no doubt that everyone is going to have to spend dollars as wisely as possible for the foreseeable future. Although cleaning the trees of mummies during the winter isn’t cheap, it is the method of NOW control where you clearly get the most bang for the buck spent. We’re really playing a numbers game here, and this is one practice that is stacked in our favor by the biology of this pest.

    For example, let’s assume a potential of 50 mummies per tree and 30 of them each have 1 NOW larvae. Half of those are female, and each female lays approximately 85 eggs. At harvest in late July we’re into the third generation, and for arguments sake let’s assume there’s no natural mortality.

    Look at what could theoretically happen to the worm population in one Nonpareil tree with 30 infested over-wintering mummies and no control:

    • 1st generation: 15 females x 85 eggs/female = 1,275 larvae
    • 2nd generation: 1,275/2 (half female) x 85 eggs = 54,188 larvae
    • 3rd generation: 54,188/2 x 85 = 2,302,990 larvae per tree at harvest!!!
                        (Thankfully, there IS natural mortality or else we’d be knee deep in worms!)
    Now, look at the impact of a hull split spray aimed at the second NOW generation. We know that sprays give at best about 60 percent control. This reduces the population but is not nearly as good as sanitation as you will see.
    • 2nd generation: 54,188 larvae x 40% survival after the spray = 21,675 larvae
    • 3rd generation: 21,675/2 x 85 = 921,196 larvae per tree to attack the crop at harvest.
    Now, look at what sanitation does in comparison. Start with the same 30 infested mummies per tree, then winter clean down to 2 mummies per tree. One is female, one is male.
    • 1st generation: 1 female x 85 eggs/female = 85 larvae
    • 2nd generation: 85/2 (half female) x 85 eggs = 3,613 larvae
    • 3rd generation: 3,613 larvae/2 x 85 = 153,531 larvae per tree at harvest.

    (If you can beat the 3rd generation by an early harvest you’re even further ahead.)

    So, a hull split spray reduced the worm population by 60 percent, but sanitation by itself, without spraying, reduced the population by 94 percent! When more NOW larvae make it through the winter, more egg laying will occur next season regardless of what else you do. In relation to the number of mummies left in the tree, expensive chemical treatments next season will only slow the rate of worm damage increase.

    If you have scarce dollars to spend on NOW control, spend them this winter when they will do the most good in a sanitation program. If the entire neighborhood works at this, the positive effect will be multiplied many times over for everyone. If you’ve got neighbors that don’t seem to get it, cleaning your orchard will still be a tremendous help to you. If you have no mummies, the first generation in the spring won’t be able to build up and establish a population in your orchard. You’ll benefit since they’ll have to fly in from the neighbors after hull split before they can begin to hurt your crop.

    Be sure to finish the job by destroying the infested nuts once they’re on the ground. Mow and shred the mummies before March 1st so NOW moths don’t have a chance to emerge. When you’re enjoying mowing during bloom in the spring, take personal satisfaction in seeing the chips and pieces of almond fragments and mangled worm parts fly out from under your mower! — By Joseph Connell, UCCE Farm Advisor Emeritus, Butte County

  • 2023-2024 Winter Chill, Dormancy & Walnut Management Update

    Walnuts are one of the highest chill requirement tree crops in California. Though it’s easy to forget given the luxuriously high amounts of chill last year, multiple recent winters have fallen short of the chill accumulation needed for a tight, economical walnut bloom (e.g. 2014, 2015, 2020). Inadequate winter chill accumulation can result in delayed budbreak, scattered or prolonged budbreak and buds on southern sides of branches never opening. Prolonged bloom can result in a wider variety in nut sizes, more small nuts, and multiple shakes, while also complicating timing of control measures for blight or husk split pests. In the next 20-40 years, Central Valley walnut orchards will get 14-20% less winter chill than in the 1950s when many of our grandparents were farming. Anecdotal experience suggests the chilling requirement for ‘Chandler’ is around 60-65 chill portions as quantified by the Dynamic Model. Given decreased chill projections it is likely that currently planted ‘Chandler’ orchards will not meet their chilling requirement in at least one out of ten years in most of the Central Valley in the coming decades, if left to their own devices. While we wait for high quality lower chill varieties to develop, how can walnut growers manage the chilling requirements of the orchards in the ground now? This has been the topic of many recent years of UC research with funding from the California Walnut Board and the California Department of Food and Agriculture.

    Looking at a sampling of four CIMIS weather stations using the UC Fruit & Nut Center chill calculator tool, on average the Sacramento Valley has accumulated 41 chill portions to date (written January 14th). This is about 20% below last year, and more in keeping with the winter of 2019-2020. While 2019-2020 was a low chill accumulation winter, that was due in large part to a fairly warm February. Thus, it’s too early to say if this is a year in which dormancy breaking treatments would be beneficial. Keep an eye on the UC Fruit & Nut Center’s chill calculator. Nonetheless, it’s good to be aware for future winters that there are options in the toolbox.

    For three winters, we have been studying the impact of a number of dormancy breaking treatments to give growers tools to deal with low chill winters (see here for more detail on previous years). Rather than wait for low chill years to come along, we’ve created warm winter conditions in large, open-top chambers that we’ve built around mature Chandler trees at the UC Davis campus. These trees were coupled with unheated trees that got sufficient winter chill. Approximately 30-40 days before (what we hoped would be) budbreak, dormancy breaking treatments were applied to different scaffolds in each tree. We then monitored budbreak over many weeks to quantify timing of 50% budbreak, the duration of budbreak and the percent of buds that opened on a scaffold.

    Over the course of three years, we’ve tested hydrogen cyanamide, often marketed as Dormex®, a blend of nitrogen compounds marketed as Erger®, an analogue of the plant hormone cytokinin, marketed as Mocksi®, and calcium ammonium nitrate (CAN-17), all of which were compared with a water control. Dormex is the only one of these products currently labeled for use as a dormancy breaker in walnuts (see label for more use details). Erger and CAN-17 are labeled as fertilizers. Over the last two years (2021 and 2022), we found that at least in terms of budbreak timing, it appears Dormex at 2% and 4% and CAN-17 at 20% could prompt heated scaffolds to behave like they had received enough chill, whereas Erger at 6% only partially compensates for lack of winter chill. Dormex at 4% moved timing even earlier than the sufficiently chilled control, whereas Erger moved the timing but only about halfway between the timing of the heated control and the sufficiently chilled control. No effect was seen using Mocksi over two years.

    This previous winter-spring, we put Dormex at 2% and 4% head-to-head. Given that last year was a very high chill winter, it was hard to force insufficient chill accumulation, even with our heated tents. Ambient trees accumulated 78-82 chill portions, while heated trees accumulated 10-12% less, 69-74 chill portions. Both Dormex at 2% and 4% moved terminal and lateral budbreak timing on the heated trees to similar values as seen in the unheated control, in essence compensating for the chill difference. Dormex at 2% also increased the percent of buds that opened, to values as high (lateral buds) or higher (terminal buds) than the unheated control scaffolds. Budbreak percent was not different between Dormex at 4% and the water control within heated or unheated trees. In other words, under these conditions of 69-74 chill portions, it would not have been beneficial to use Dormex at a rate higher than 2%. However, even given this range of chill accumulation, which is considered sufficient, 2% Dormex increased lateral budbreak from 29% to 42% and terminal budbreak from 89% to 98%. That said, in unheated trees, which accumulated 78-82 chill portions, there was no significant increase in budbreak from Dormex use at either rate.

    With generous collaboration from two grower hosts, we also compared Dormex at both 2% and 4% and CAN-17 last year at a field scale, to be able to collect yield data, in addition to budbreak data. At one healthy orchard just a few years into its prime yielding years (10th leaf) near Glenn County, where 73 chill portions accumulated (similar to heated trees on campus), we saw the same change in budbreak timing (3 days earlier) across each treatment when compared to no treatment. This did not lead to significant differences in yield, contrary to what the increased percentage of budbreak in the campus heated tented trees might have led us to expect. Yields ranged on average from 6,240-6,690 lb per acre across treatments. Across size quality measurements (percent jumbos, large, average nut weight, edible yield), nuts from the Dormex treatments were not significantly different from the control, though relative to the control nuts, the CAN-17 treatment had a lower average percentage of large and jumbo nuts (52% v. 64%) and lower average weight (9.15 g v. 10.09 g). There were no differences in color quality as measured by reflected light index (RLI) among any of the treatments.

    At the Chandler orchard at the Nickels Soils Lab, where 82 chill portions were accumulated (similar to unheated trees on campus), there was a small but significant change in timing of budbreak in each treatment relative to the control (3 days). Surprisingly, however, there was also an increase in yield in the 4% Dormex treatments relative to the control, yielding on average more than 1,400 lb more per acre (5,216 lb vs. 6,857 lb). The average yields in the Dormex at 2% treatment and the CAN-17 treatment were also numerically higher than the control (1,019 lb higher and 719 lb higher, respectively), but there was a great deal of variability in different replicates, making it difficult to statistics to decipher if yield differences can be attributed to the treatments. There were no differences between any of the treatments and the control treatment across size quality measurements (percent jumbos, large, average nut weight, edible yield) or color quality (RLI).

    It is perilous to draw conclusions about dormancy treatment efficacy at a field scale based on one high chill year’s data. The difference in yield effects at the Glenn County orchard and Nickels Soils Lab is intriguing. The Nickels site is an older orchard at a tighter spacing, suffering from significant limb dieback from shading coupled with Botryosphaeria infections. One possible explanation for the yield difference would be that the Nickels site benefitted from treatments that encouraged additional budbreak, whereas at the healthy, high yielding Glenn County orchard there was already sufficient budbreak without intervention. Knowing that June drop generally reduces cropload, it’d make sense that increased budbreak, as we saw in the campus trees with 2% Dormex, would not necessarily lead to increased yield. Given high chill accumulation in healthy orchards, dormancy breaking treatments are unlikely to pay for themselves at current walnut prices. If chill accumulation is lower than ~60 chill portions, our heated tent data indicates they may pay for themselves, but we’ll need yield data at production scale to know for sure. The Nickels results point to the possibility that dormancy breaking treatments may be of use in orchards with limb dieback. At the same time, we need to be cautious to watch for swings in yield this coming year that may result from over-taxing the already struggling trees. Particularly given how tight walnut budgets are these days, I’d wait for more data before trying out this orchard-renewal strategy at a large scale if I were a grower.

    We’ll continue this project with funding from the California Department of Food and Agriculture to improve understanding of ideal rates and timings, and the physiological response to these treatments inside the trees. Stay tuned! — By Katherine Jarvis-Shean, Orchard Systems Advisor UCCE Sacramento-Solano-Yolo

  • Preventing Bacterial Blast Damage in Almond This Year

    In 2023, the cold, wet weather during bloom and leaf-out resulted in bacterial blast damage in many Sacramento Valley almond orchards. If conditions this year are cold and wet during bloom, we may see a recurrence of blast: make a plan now to keep blast damage to a minimum.

    The Bottom Line:

    • Bacterial blast can be a problem when cold, wet conditions coincide with bloom or leaf-out.
    • Copper resistance is common in the pathogen: spraying copper is ineffective for preventing blast in many orchards.
    • Frost protection is the most economical prevention option and will help prevent damage from both frost and bacterial blast.x
    • The antibiotic kasugamycin (Kasumin®) is effective for preventing blast when applied up to 7 days before cold, wet weather. It has received approval for availability this year under an emergency exemption registration (Section 18) but is not currently labeled for almond under a full registration (Section 3).The Details:

      Pseudomonas syringae pv. syringae (Pseudomonas) is a bacterium which can infect all aboveground parts of an almond tree. If leaves, flowers, or spurs are infected, the resulting disease is bacterial blast. Pseudomonas is ubiquitous in orchards, so bacterial blast is likely to develop whenever environmental conditions are cold and wet, which favors this disease. Pseudomonas is spread by water hitting the trees, either from rain or sprinklers. If this wetting occurs at the same time as frost damage, Pseudomonas can enter the tree through cells damaged by freezing. Trees are especially susceptible to frost damage during bloom and leaf-out, when tender new growth is exposed to cold temperatures.

      Preventing infection by Pseudomonas is the only way to control bacterial blast. Frost protection in an orchard is your best defense and your most inexpensive prevention strategy: if the trees are not damaged by frost, Pseudomonas will not be able to enter the tree to cause disease. As a second line of defense, research has shown that kasugamycin (Kasumin®) is effective for preventing bacterial blast when applied no more than 7 days before cold, wet weather. Note that kasugamycin is currently not labeled for use in almond, but has become available this season due to a Section 18 exemption. If the weather warrants treatment, kasugamycin can be used as a preventative spray up to two times during bloom. For this spray, complete coverage is crucial for control: all tender new growth must be covered in a protective layer of the antibiotic for it to be effective. Any tissue left uncovered will be unprotected.

      What about copper? Current work by UC researchers shows that copper-resistance is common in Pseudomonas throughout the state. Many of the orchards heavily affected by blast in 2023 received multiple dormant sprays containing copper. In some cases, mixing mancozeb with copper may provide some level of control, but research shows that this mixture is not as effective as kasugamycin and the copper can cause phytotoxicity. — By Jaime Ott, UCCE Tehama, Shasta, Glenn, and Butte Counties

      For more information on bacterial blast, check out these articles at sacvalleyorchards.com

      Bacterial blast/canker: What do we know? – an update on the factors predisposing orchards to damage by bacterial blast, and more details about control strategies for bacterial blast

      Bacterial Blast and Canker – a good description of the various symptoms seen with bacterial blast

  • 2023 UCCE Blackeye Bean Variety Evaluation

    UC Cooperative extension experts led by Michelle Leinfelder-Miles evaluated blackeye bean varieties in a commercial field in Stanislaus County in 2023. The season began with cool and wet spring conditions, which lasted through the month of June and delayed planting. Seven varieties from the University of California blackeye breeding program were planted on July 7th. The varieties were grown on a Hanford sandy loam, and the soil temperature was approximately 75°F at the time of planting. Each variety was planted across six rows on 30-inch spacing, on a row length of approximately 275 feet. The seeding rate was 40 pounds per acre. This was a non-replicated evaluation due to a limitation in seed; therefore, no statistical analysis is presented.

    The trial was planted in a field of CB46, and fertility and pests were managed by the grower in the same manner as the field. Data are presented in Table 1. Stand counts were made approximately two weeks after planting on July 20th. The stand was assessed as the number of plants per two-foot length. Twelve replicate counts were averaged. We evaluated aphid and lygus damage on September 8th, which were low due to the grower’s management. For lygus, we took 10 sweeps from four locations in each plot and counted the lygus. Data were averaged and are presented as a 10-sweep count. For aphids, we used a rating scale from 0 to 10 that accounted for visible crown damage and aphid incidence. In addition to the in-field assessment of lygus, we also evaluated harvest samples for stings and found that, on average, about 1.2 percent of the beans had lygus damage. No diseases were observed.

    We harvested on November 6th. All six rows of each variety were cut and raked into one windrow. At the time of cutting, the grower observed that CB77 plants were laying flat, but they were laying in such a way that the knives still picked up the plants. The grower also observed that CB74 had an upright growth habit that could potentially make it a variety viable for swather cutting. We evaluated 100-seed weight as a measure of seed size, evaluating five 100-seed samples per variety.

    We would like to thank the cooperating grower, the CA Crop Improvement Association for funding regional trials, and the CA Dry Bean Advisory Board for assistance with statewide research prioritization and assistance with outreach. — Images & Article By Michelle Leinfelder-Miles, UCCE

    Table 1. 2023 Blackeye Bean Variety Evaluation Results

  • UCCE 58th Annual Sweetpotato Meeting

    Save the date, Thursday February 8, 2024, for the UC Cooperative Extension 58th Annual Sweetpotato Meeting to take place at the UCCE Classroom (2145 Wardrobe Ave., Merced).  Growers and industry stakeholders are invited to attend and gain research updates on sweetpotato production and marketing in California. Doors open at 7:30 a.m. where attendees can sign-in, and enjoy some coffee and Jantz Sweetpotato muffins.  The meeting will run from 8AM to noon, and conclude with lunch.  Following lunch, the Sweetpotato Council of California will convene their BOD Meeting.  See the Annual Sweetpotato Meeting agenda below: