California Ag Network

Tag: UCCE

  • How to Protect Your Almonds from Navel Orangeworm and Other Pests

    With spring weather arriving earlier, almond growers in California can expect an earlier influx of pests in their orchards — and to get started sooner on preventing them from harming their nut crops. According to UCCE Sacramento Valley Integrated Pest Management Supervisor Sudan Gyawaly, now is the time to watch out for things like navel orangeworm (NOW), peach twig borers, leaf-footed bugs and spider mites.

    Navel Orangeworm (NOW)

    Navel orangeworms (Amyelois transitella) are the most prominent pests in almond orchards. These moths lay their eggs on the shells after hull split, and the larvae burrow inside the shell, eating the nuts and sheltering inside. Signs of a NOW infestation in an orchard include:

    ·      Small, flat, oval-shaped eggs outside of almond hulls

    ·      Pinhole-sized holes in almond hulls

    ·      Hulls that are oily in appearance

    ·      Fungal infections of nuts

    ·      Extensive webbing inside the hulls

    ·      Partially eaten nuts

    ·      Larvae that are white to pink in color, with crescent marks behind the head

    Navel orangeworm damage to an almond. Photo by Matthew Malcolm

    To manage NOW in your orchards, be sure to continuously monitor male flight activity by using pheromone traps. Also continue to monitor NOW egg traps to establish a spring biofix (the first spring flight, which acts as the starting date for calculating growing degree days), to help you predict the timing of their later flights. The first flight usually occurs from late March through April, but earlier times are possible, depending on the weather.

    According to UC IPM, prevention is key to avoiding infestation. This includes removing all mummy nuts by the start of February. To eliminate existing NOW populations:

    ·      Establish a biofix

    ·      Hang pheromone dispensers in the trees to disrupt mating

    ·      Assess trap activity and begin spraying at hull split.  Apply pesticides at night and early morning for optimal results

    ·      Harvest and clean up as early as possible

    ·      Remove mummy nuts by March 15 of the next year.  Mow or disk mummies on the ground.

    Peach Twig Borer

    While less of a concern in mature orchards, peach twig borer — also a moth — can still be a menace for almond growers in younger fields by causing primary scaffold damage. Begin monitoring pheromone traps in April to establish a biofix and decide if a spray is necessary in May.  Consult with your pest control adviser if you are unsure.

    Leaf-Footed Bugs

    Stink bugs and leaf-footed bugs are especially troublesome after a warm winter. Leaf-footed bugs can be trickier to spot.  UC IPM lists the tell-tale signs of an infestation in your orchard as:

    ·      Gummy nuts — nuts with exudates on the outside of the hull — a signature warning

    ·      Nuts that have dropped prematurely

    ·      Black spots on kernels and wrinkled, misshapen nutmeat from adult feeding

    ·      Withered and aborted shells from bugs feeding on premature nuts

    Leaf-footed bug

    Stink bugs cause similar damage, but this is usually around May or June. Leaf-footed bug management can vary from orchard to orchard, depending on history and severity. Gyawaly advises basing spray decisions on this history plus on damage risk associated with seasonal conditions. Consult with your pest control adviser if you are unsure.

    Spider Mites

    Typically found in the lower parts of the canopy, spider mites may also come out earlier and in greater numbers with warmer weather. Their presence should be monitored once every two weeks.  For this pest, beneficial arthropods that prey on spider mites may be one of your orchard’s best friends. These species include:

    ·      Western predatory mites

    ·      Spider mite destroyers

    ·      Sixspotted thrips

    ·      Pirate bugs

    By monitoring and addressing mite and insect pests in the spring, the pest populations can be kept under control to ensure a large, high-quality almond harvest.

  • Groundwater Markets Tested in Mojave Basin

    As growers navigate SGMA, different avenues are being explored for access to the needed water for crops, including groundwater markets. This has been experimented with in the Mojave Basin, resulting in stabilized implementation  and aggregate gains, but also a consolidation of water rights. At the World Ag Expo, UC Cooperative Extension Associate Professor Ellen Bruno discussed the findings on groundwater markets with Matthew Malcolm at California Ag Network. Watch this quick video and read more in California Fruit & Vegetable Magazine.

    Please thank this video’s sponsor Simplot for their industry support.

  • 2025 Results of Pre-Emergent Herbicide Demonstration Trial for Walnut

    The 2025 UCCE walnut pre-emergent herbicide demonstration trial is completed, and the results show strengths and weaknesses of 19 different herbicide treatments, applied either in February or March.

    Takeaways:

    1. All treatments were applied with a strong post-emergent mix, but hairy fleabane and white clover were not adequately controlled with post-emergent treatments alone. Control was dependent on the addition of an ALS inhibitor herbicide (products like Craze, Matrix, or Mission).

    2. Summer annual weeds were best controlled by products with long residuals (products like Alion, Chateau, Brake On! (not registered in CA), and Prowl.

    3. Yellow nutsedge was controlled by treatments with Zeus or Craze.

    4. Conclusion: Pre-emergent treatments in late winter must account for winter annual weeds that have already emerged and perennial weeds while also maintaining good residual control further into the summer.

    Introduction

    Winter pre-emergent herbicide applications are critical to get right if yearly weed management operations are going to be successful in walnut orchards. Poor selection of herbicides or missed timing could make the difference between good control and battling an overwhelming infestation of weeds. In walnut orchards I have regularly heard two comments concerning pre-emergent herbicide applications in walnut orchards:

    1. Those who apply pre-emergent herbicides in the fall, just after harvest, tend to have the cleanest orchards.

    2. February or March are the most common times to apply pre-emergent herbicides in walnut orchards.

    Maybe my perception is incorrect, but these weed control strategies seem to be at odds. When it comes to winter annual weeds, it is likely safest to apply pre-emergent herbicides before germination due to several common weed species with herbicide resistance issues (hairy fleabane, Italian ryegrass, annual bluegrass). Applications later in the winter will have to deal with emerged weeds, potentially resulting in more escapes and misses.

    However, herbicide treatments in February or March are common, and many growers have been successful with these treatments. Why is this, and what is the key to achieving good control later in the winter? Success at later timings depends on how much post-emergent activity you are getting out of your tank mix. Some pre-emergent herbicides can contribute to your post-emergent activity. Common pre-emergent herbicides like Goal, Chateau, Matrix, Pindar, and others add some extra post-emergent activity to tank mixes when used in winter months. Dr. Brad Hanson (UCCE Weed Specialist at UC Davis) discussed this topic when he addressed tank mixes of Alion and Matrix in his UC Weed Science Blog article (linked here). My recent work with rimsulfuron on established johnsongrass also explored this subject (linked here). These prior discussions focused on rimsulfuron products as tank mix partners for pre-emergent applications, but I wanted test a broader range of products applied in February and March. This year’s walnut preemergent herbicide demonstration made some progress toward that goal.

    I will discuss my findings next, and at the end of this article I have included results tables. All products except one are currently labeled for use in walnut orchards, though with some restrictions on orchard age. The one unlabeled product in this study was Brake On!, manufactured by SePRO, currently pending registration in CA. This is not an exhaustive list, and the data provided here does not constitute a recommendation of any product.

    Trial design

    In 2025, I arranged my pre-emergent demonstration trial to evaluate individual products and tank mixes for weed control efficacy when applied in February and March. This trial was installed in the Loybas Hill region of Tehama County, in a 4-year-old walnut orchard with Tehama silt loam soil. A post-emergent mix of 2 qt/A Roundup Powermax 3 and 2 qt/A Rely 280 was added to every plot in February, and pre-emergent herbicides were applied either in the mix, or one month later in March. The tables at the end of this article show the full list of treatments and when they were applied. The first table represents weeds that were present at application, hairy fleabane and white clover. The second represents weeds that grew to be prominent in May and June, so their control depended on residual activity from my herbicide treatments lasting long into the summer.

    Results overview

    White Clover and Hairy Fleabane (Table 1): Both weeds were controlled by all three group 2 herbicides tested: Craze, Revolt, and Mission. Revolt was weaker on fleabane while Craze was weaker on clover and these differences also showed up in the tank mix treatments with both products applied with Prowl. February and March treatments with these three herbicides produced very similar results. The 12 fl oz/A rate of Chateau also effectively suppressed both species.

    Summer annual weeds (Table 2): The primary weeds in the categories recorded here were grass weeds (jungle rice and large crabgrass) and broadleaf weeds (prostrate knotweed, spurge, and pigweed). Many herbicides provided good control until June (3-4 months after treatment) but only Alion, Brake on! (not currently labeled for CA), and March-applied Mission maintained “good” control of broadleaves through July. Only Alion and Prowl maintained “good” control of grasses through July.

    Yellow Nutsedge (YNS; Table 2): Zeus was the best tested product for nutsedge control, but Craze also showed some effects in July by keeping nutsedge coverage low. Rimsulfuron products like Matrix and Revolt are also labeled for YNS control, but labels suggest sequential applications, and the application timings used in this trial may not have been ideal to target YNS with this product.

    Summary and cautions:

    This is a single trial only representing one weed population and one soil type, so results may vary by location. However, hopefully this demonstrates the importance of tank mixing to control emerged weeds as well as future emergence. Group 2 herbicides like Revolt, Mission, and Craze can provide good post-emergent control in addition to their pre-emergent activity. But be cautious, this herbicide group is notorious for herbicide resistance. Do not overuse this class of herbicides or you will likely start seeing weeds escaping your treatments.

    Look through the following tables if you are interested in seeing more information on efficacy in these trials. To see weed coverage data, view the report on the UCCE Tehama website here. Thanks to the California Walnut Commission for supporting this work. For any questions or additional information, contact Ryan Hill at 530-527-3101 or rjahill@ucanr.edu. — By Ryan Hill, UCCE Agronomy and Weed Science Advisor, Tehama County

    Weed control tables:

    Control was determined by calculating % reduction in weed coverage, relative to the plot with the worst infestation. Control is summarized by four categories. These categories may not represent each grower’s threshold of tolerance for weed control, but they can still provide relative comparisons between the products tested.

    Poor control is indicated by a “p”, representing control between 0 and 50%.

    Moderate control is indicted by an “m”, representing control between 50 and 70%.

    Good control is indicated by a “g” and highlighted light green, representing control between 70 and 90%.

    Excellent control is indicated by an “e” and highlighted dark green, representing control between 90 and 100%.

    Table 1: The effect of different pre-emergent herbicides on two weeds that were present at application, hairy fleabane and white clover.

    Table 2: The effect of different pre-emergent herbicides on weeds that germinated or sprouted in summer. Summer annual broadleaves included prostrate spurge, knotweed, and pigweed and summer annual grasses were primarily crabgrass and jungle rice.

  • Variety and Neighboring Crops are Predictors of Leaffooted Bug Risk in Almond

    Leaffooted bug is a sporadic pest in almond, but damage can be significant in years when pest pressure is high. The pest may evade early detection by growers and PCAs because it overwinters as adults in vegetation outside of the orchard and tends to colonize the upper tree canopy, rendering it generally out of sight. As a result, pest pressure is often realized after damage has occurred. The damage may vary considerably between almond varieties, adding yet another challenge for diagnosis.

    In Tulare County, heavy leaffooted bug damage was observed in May 2025 in almond orchards surrounded by citrus.  Adult leaffooted bugs (Figure 1A) overwintered in the citrus and then entered the neighboring almond orchards in March and April. By early May, symptoms of infestation included extensive nut drop (Figure 2A) and gummosis on the nuts (Figure 2B). Although the adults were not observed in the orchard, the pest was identified based on the observation of the characteristic egg strands of leaffooted bug (Figure 1B). In orchards with Nonpariel and Aldrich, both varieties were affected; however, the nut drop was more extensive in Aldrich than Nonpareil (Figure 2A).

    The full impact of the pest may not be realized until harvest because the quality of affected nuts remaining on the tree may also be compromised, thus reducing crop value. Nuts that are stung in late April to early July can be severely shriveled, have sunken lesions, or a brown spot depending on how developed the kernel was prior to feeding (Fig. 3, row 2-5).  These nuts stay in the tree, are harvested, and can significantly increase the percentage of nuts classified as inedible during nut quality assessments.  When examining a library sample of damaged kernels at harvest, nuts damaged by leaffooted bug fall into the same category as stink bug damage, as kernels damaged by these two pests are indistinguishable.

    In 2007, UCCE Kern County Farm Advisors David Haviland and Mario Viveros had the opportunity to evaluate the relative susceptibility of 15 almond varieties to leaffooted bug damage. That year, leaffooted bug invaded a Kern County variety trial research block that included 15 varieties planted in replicated, randomized blocks. This unique situation allowed for unbiased evaluation of the performance of varieties under equivalent pest pressure. Results indicated that the average number of aborted nuts per tree ranged from 0 to 33% of the total crop. Additionally, at harvest, the estimated rejects from leaffooted bug damage ranged from 0 to 30% of the harvested yield. Researchers also noted that crop loss varied by variety, with Fritz exhibiting the highest crop loss at 63%, followed by Sonora, Aldrich, Livingston, Monterey and Carmel.  The other varieties in the block had 3% or less total damage from the pest.

    The underlying basis for the differential susceptibility of almond varieties to leaffooted bug is unknown. Damage does not appear to be related to harvest date or shell hardness at harvest. Other factors such as plant volatiles, hull thickness, or shell hardness in April and May when the bugs are present may play a role in varietal susceptibility. Haviland and Viveros also noted that varietal susceptibility is somewhat relative, explaining that Wood Colony exhibited low susceptibility to leaffooted bug in the research plot, but significant damage was reported on Wood Colony in commercial orchards when combined with less susceptible varieties (ie. Nonpariel and Carmel).  These observations indicate that leaffooted bug prefers certain varieties, but in the absence of a preferred variety, the pest will remain in the orchard and feed on the most preferable variety of the less-preferred varieties present in the orchard.

    The 2025 observations in Tulare County, taken in consideration with the 2007 data from the UCCE variety trial suggest that the best way to monitor leaffooted bug is to focus attention on the most susceptible variety in the field. Gummosis and nut drop in the most susceptible variety will serve as an indicator of pest pressure in a given orchard. Growers with Fritz, Sonora, Aldrich, and Livingston should be extra vigilant in monitoring pest pressure.  Haviland and Viveros note that orchards composed of relatively unsusceptible varieties will have characteristically lower risk of leaffooted bug damage. Additionally, growers and PCAs should consider pest pressure from surrounding orchards and landscape plants that may serve as overwintering sites for the adults, thus contributing to the cryptic nature of the pest.

    Management programs for leaffooted bug consist of monitoring for the pest and spraying primarily with pyrethroids, when needed. Pest management guidelines for leaffooted bug and other pests can be found at www.ipm.ucanr.edu and reports of Almond Board of California-sponsored research can be found at https://www.almonds.com/research-database. — By Elizabeth Fichtner, UCCE Farm Advisor, Tulare County, and David Haviland, UCCE Entomology Advisor, Kern County

    Figure 2. Aborted nuts were prevalent on Aldrich, but the neighboring Nonpareil exhibited minimal damage (A). Gummosis and egg strands on aborted nuts indicated leaffooted bug damage (B).

    Figure 3. Leaffooted bug predation affects the quality of nuts remaining on the tree. Unaffected nuts are represented in row 1; affected nuts of varying quality are represented in rows 2-5.

    Figure 1. Leaffooted bug adults (A) are difficult to scout. Pest pressure is evident by the gummosis at feeding sites and the deposition of eggs in strands (B). Alternate hosts may harbor overwintering populations of leaffooted bug (C and D). Photos A, C, and D: W. Bentley.
    Figure 2. Aborted nuts were prevalent on Aldrich, but the neighboring Nonpareil exhibited minimal damage (A). Gummosis and egg strands on aborted nuts indicated leaffooted bug damage (B).
    Figure 3. Leaffooted bug predation affects the quality of nuts remaining on the tree. Unaffected nuts are represented in row 1; affected nuts of varying quality are represented in rows 2-5.

  • SoCal Youth Inspired by UCCE Advisor’s Passion for Water Conservation

    May is Water Awareness Month, a special time for Californians to come together in celebration of water, our most essential shared resource. Across the state, water agencies and providers are hosting lively events, such as poster contests and family-friendly activities, that promote conservation and spark curiosity.

    “Now is a great time to visit your local water provider’s website to learn how you can get involved,” said Esther Lofton, University of California Cooperative Extension urban watershed resilience advisor for Orange, Los Angeles, Riverside and San Bernardino counties.

    Esther Lofton, UC Cooperative Extension urban watershed resilience advisor, discusses water quality issues with 12th graders at UC South Coast Research and Extension Center.

    Earlier this May, Lofton and her team actively engaged eight groups of 12th-grade students from Orange and Los Angeles counties. As part of a GROW Program event at UC South Coast Research and Extension Center in Irvine, she brought water science to life by exploring the intricacies of filtration systems and the remarkable journey water takes to reach our taps.

    Lofton’s colleague, Daniel Gonzalez II, energized the sessions by demonstrating parts of the filtration process and guiding students through hands-on activities.

    Students were surprised to learn about the complexities of water sourcing. “I didn’t know we import water from as far as Colorado!” one of them said.

    To foster a sense of ownership and responsibility, Lofton encouraged the approximately 280 participating students to make personal pledges for water conservation. Their enthusiastic responses included promises to turn off the tap while brushing their teeth and to fill washing machines completely before use.

    One memorable moment came when a student humorously stated: “I will drink less water!”

    Lofton chuckled and reminded the class: “If your body needs it, I encourage you to drink more water – that’s the only exception!”

    Orange County grade schoolers wowed by ‘magic’ of water science

    Lofton and her team also attended the OC Children’s Water Education Festival, hosted by the Orange County Water District in late April, where they captivated more than 1,600 enthusiastic third- to fifth-graders.

    Over two days at Oak Canyon Park, the educators conducted 13 interactive sessions, each with approximately 45 students, guiding them on the extraordinary journey water takes from source to tap while reinforcing the importance of conservation.

    The enthusiasm of the young crowd was palpable, with many exclaiming “this is magic!” as they watched water flow cleanly from the filter.

    “I really try to ignite a sense of responsibility in this next generation about their critical role in sustainable practices,” Lofton said.

    Beyond the classroom, Lofton and Gonzalez also amplified their message through social media and blog posts, creating opportunities for community feedback and questions.

    One resident from Santa Barbara asked: “If California cares about protecting water, why are they also building more houses?” This inquiry stimulates essential discussions about finding the balance between growth and sustainability.

    Lofton is keeping the conversation going by inviting community members to participate in a brief survey and share their personal water conservation pledges.

    “We all live in watersheds, and every small action contributes to a greater impact,” Lofton said. “By making a pledge, you’re not only contributing to a more sustainable future, but you’re also helping lead by example.”

    Selected pledges will be featured in next year’s Water Awareness Month celebrations, highlighting the meaningful ways individuals are making a difference.

    To learn more, explore Lofton’s latest blog post on Water Awareness Month. You can also follow her journey and access additional resources on Instagram, TikTok, and X, or visit her UC ANR SoCal Water Resources website, which features engaging resources on drinking water, water resilience, water use efficiency and more.

    UC Agriculture and Natural Resources brings UC information and practices to all 58 California counties. Through research and Cooperative Extension in agriculture, natural resources, nutrition, economic and youth development, our mission is to improve the lives of all Californians. Learn more at ucanr.edu.

  • CalFresh Healthy Living, UCCE Reaches Every Head Start Student in Calaveras County

    In Calaveras County, a preschooler was helping his instructor pick up some class equipment when he announced proudly: “I’m really strong because I eat a lot of protein!”

    “That’s right!” replied Mary Manning, a CalFresh Healthy Living nutrition educator with the University of California Cooperative Extension’s Central Sierra office. “And protein makes you what…?”

    “GROW!” proclaimed the young boy, flexing his muscles.

    This vignette illustrates the memorable impact of programs administered by CalFresh Healthy Living, UC – one of the organizations in California that teaches nutrition and promotes physical activity for people eligible for SNAP, the Supplemental Nutrition Assistance Program. UCCE educators – affiliated with UC Agriculture and Natural Resources – deliver the lessons throughout the state.

    Manning partners with The Resource Connection, a nonprofit based in San Andreas, to offer nutrition programs at six Head Start and two Early Head Start sites across Calaveras County.

    “Our program reaches every single Head Start student in the county, which I think is fantastic because it sets the template and lays the groundwork for health in these kids’ lives,” said Noah Cooke, community education supervisor for CalFresh Healthy Living, UCCE Central Sierra. “They’re learning – as three-, four-, and five-year-olds – skills that are going to be useful when they’re 74 or 75 and beyond.

    Noah Cooke

    In addition to delivering nutrition lessons for the 113 preschoolers currently at the eight sites, the CalFresh Healthy Living, UCCE team incorporates physical education activities, as well as useful newsletters and virtual meetings for family members. After a pause due to COVID, The Resource Connection staff and participants were delighted when in-person programs restarted in fall 2023.

    “The goal is to reach students and families on a lot of different levels,” said Cooke, who also works with CalFresh Healthy Living, UCCE educator Mariana Garcia to support programs across the region.

    Cooke noted that the preschoolers are only just beginning their health and well-being journey with CalFresh Healthy Living, UC programs. After the young students graduate from the Head Start program, they will continue to benefit from nutrition education programs at the elementary, middle and high school levels. By partnering with teachers, administrators and site staff across Calaveras County, CFHL UCCE served nearly 1,600 students in schools and before- and after-school settings from October 2023 through September 2024.

    Physical activities engage young students in lessons

    While the frequency and content of her visits vary across the various sites and facilities, Manning – who was trained in classical ballet and has extensive experience teaching dance to children – always incorporates a lot of movement and energy into her lesson plans.

    As part of the curriculum, educators incorporate energetic physical activities, such as “parading around” the yard, for the Head Start students.

    In addition to “parading around” cones while pretending they are sharks, crabs or other animals, the young students also especially enjoy making the gestures that symbolize the “Go, Glow, Grow” nutrition curriculum.

    For “Go” foods like grains and carbohydrates, they run in place. For “Glow” foods like fruits and vegetables that make their hair shine and eyes sparkle, they touch their hair and wiggle their fingers by their eyes. For “Grow” foods like protein and dairy, they flex their muscles and jump up and down.

    Manning has heard from the Head Start teachers that the students’ parents are seeing those lessons in action.

    “They’re at the grocery store and their child is pointing out the different foods and what type of food it is, whether it makes them ‘grow’ or makes them ‘go’ – that’s so exciting for the parents,” Manning said.

    Mary Manning

    Another direct impact is that many of the children become more willing to taste new foods.

    “I love how Mary allows children to actively engage in trying new foods and physical activity,” said the lead teacher at West Point Head Start. “Our friends have made connections through nutrition, physical activity and a healthy body.”

    At the end of each visit, Manning incorporates a sampling of foods related to the theme or lesson for the day. While the fruits are almost universally well-received, some of the young ones are more reluctant to taste the vegetables. Manning teaches them a positive alternative to rejecting a particular item.

    “I’ll urge them to say, ‘not today,’” she explained. “I don’t want to them say ‘I don’t like it’ because they might like it tomorrow or the next day – or in five years!”

    Newsletters highlight healthy recipes for families

    Just as the children are trying new things in class, their parents and family members are trying new recipes, thanks to monthly “Harvest of the Month” newsletters written in English and Spanish. Prepared by Garcia and the CalFresh Healthy Living, UCCE team, each issue highlights different ingredients and how to prepare them in novel and delicious ways.

    “We’re really just trying to incorporate healthy living into the day-by-day,” Cooke said.

    As a result of CalFresh Healthy Living, UCCE efforts, young children try healthy new foods and their families try new recipes.

    Manning puts together a different newsletter – translated into Spanish by Garcia – for families that receive items from The Food Bank, administered by The Resource Connection. She said she’s constantly trying to think of recipes that make creative use of common food bank items, such as beans, lentils and peanut butter – and different ways to incorporate fresh fruits and vegetables.

    “It’s hard when money’s tight and it’s easier and less expensive to buy that processed food and serve those,” Manning said.

    Between teaching the children in the Head Start and Early Head Start program and reaching families through the newsletter and recently launched virtual meetings, CalFresh Healthy Living, UCCE is making a real difference in the lives of community members.

    “In Calaveras County, our impact has been more than I could have ever imagined,” Manning said. “I love the work we do; I’m so thankful that I’m able to do this, because it fills me with so much joy.”

    UC Agriculture and Natural Resources brings UC information and practices to all 58 California counties. Through research and Cooperative Extension in agriculture, natural resources, nutrition, economic and youth development, our mission is to improve the lives of all Californians. Learn more at ucanr.edu.

  • Monitoring Spider Mites in Almond Orchards

    Almond growers are all too familiar with the challenges posed by pests in their orchards. Despite not being on the top of a grower’s concern list, spider mites can inflict serious damage to an almond orchard, and rather quickly if populations get out of control. However, effective monitoring and the use of beneficial insects can play a crucial role in managing these pests and ensuring a healthy almond harvest.

    Understanding Spider Mites
    Spider mites are tiny arachnids that thrive in warm, dry conditions, making almond orchards an ideal habitat. These pests feed on the leaves of almond trees, causing stippling, yellowing, and eventually leaf drop. Severe infestations can lead to reduced photosynthesis, weakened trees, and lower yields. Therefore, it is essential to keep a close eye on spider mite populations and take timely action to prevent economic losses.

    The Role of Beneficial Insects
    One of the most effective natural treatments for spider mites is the use of beneficial insects, such as six-spotted thrips. These tiny predators feed on spider mites and can significantly reduce their populations. David Haviland, a University of California Cooperative Extension (UCCE) entomology farm advisor, emphasizes the importance of relying on six-spotted thrips for mite management. These thrips are highly adaptable, reproduce quickly, and provide numerous operational benefits. They occur naturally, are free, and do not leave residues, pre-harvest intervals, or worker safety issues to worry about.

    In addition to six-spotted thrips, other natural enemies of spider mites include predatory mites and lady beetles. These beneficial insects can help maintain a balance in the orchard ecosystem, reducing the need for chemical interventions. However, it is crucial to monitor the populations of both spider mites and their natural enemies to make informed decisions about pest management.

    Effective Monitoring Techniques
    Monitoring for spider mites involves regular inspections of the orchard, particularly in dusty or water-stressed areas where mites are most likely to thrive. Checking on the underside of leaves for the presence of spider mites is the most effective way to identify them in the orchard. According to the University of California Agriculture and Natural Resources (UC ANR) Integrated Pest Management (IPM) Program, growers should check for spider mites at least weekly during the warmer months. Presence-absence leaf sampling is a useful tool for determining whether treatment is necessary. If there are 1.4 mites per leaf or 38% of leaves are infested, it is time to consider intervention to prevent the population from reaching damaging levels.

    To-Do List for Growers

    1. Seasonal Monitoring: From March to early May, monitor orchards for both predators and spider mites at least once every two weeks. Increase monitoring frequency to at least once a week from June to September when mite populations can rapidly increase.
    2. Weekly Inspections: Regularly inspect your orchard, especially in dusty or water-stressed areas, to check for spider mites. Use a hand lens to detect mite eggs, hatched spider mites, and predators.
    3. Presence-Absence Leaf Sampling: Use this method to determine if treatment is necessary. If there are 1.4 mites per leaf or 38% of leaves are infested, take action.
    4. Monitor Beneficial Insects: Assess the populations of natural enemies like six-spotted thrips, predatory mites, and lady beetles to ensure they are sufficient to control spider mites.
    5. Consider Selective Miticides: If natural predators are not enough, consider using selective miticides that are less harmful to beneficial insects.
    6. Follow ABC Guidelines: Utilize resources and guidelines provided by the Almond Board of California (ABC) for effective mite management.

    For more detailed information on monitoring spider mites, growers can refer to the guidelines provided by the UC ANR IPM Program here.

    Spider mites could pose a significant threat to almond orchards, but effective monitoring and the use of beneficial insects can help manage these pests without increasing inputs. By relying on natural predators like six-spotted thrips and other beneficial insects, growers can reduce the need for chemical interventions, lower costs and promote a healthier orchard ecosystem. — By the Almond Board of California

  • Preparing Soil for Winter can Protect Soil Health

    Farmers placed clumps of soil into metal mesh baskets, submerged the baskets into jars of water, then watched to see if their soil held together. The slake test, conducted at the Soil Health Field Day in Woodland, measured soil health. Healthier soil, which contains more organic matter and bioactivity and can better support plant growth, stays intact.

    “Participants said that it was particularly useful to see the slake test on a variety of soils to better understand the nuance of how soil health management practices such as cover cropping and reduction of tillage intensity could affect soil aggregation,” said Sonja Brodt, UC Sustainable Agriculture Research and Education Program coordinator for agriculture and environment, who attended the field day alongside Vivian Wauters, SAREP project scientist.

    Katharina Ullman, Organic Agriculture Institute training and technical assistance coordinator, left, and field day participant view results of soil health test.

    Technical assistance providers, farmers and other soil health professionals gathered at the Center for Land-Based Learning on Nov. 19 to learn about preparing soil for winter with a specific focus on how soil health impacts soil structure, as well as the ability for water to move through soil as opposed to puddling or running off a field.

    “Soil with stable aggregates can withstand this submersion and stay intact, whereas a soil with poor aggregation will fall apart in the water,” Wauters explained.

    This in-field test can produce dramatically different results, where poorly aggregated soil colors the water, while the stable, aggregated soil will leave the water column relatively clear.

    Farmers were invited to bring their own soil samples to perform slake tests at the field day. Kabir Zahangir, USDA Natural Resources Conservation Service regional soil health specialist, compared soils from different management practices and discussed how to assess aggregate stability and soil water infiltration.

    Margaret Lloyd, UC Cooperative Extension small farms advisor for the Capitol Corridor, and Lindsey Kelley, UCCE small farms community education specialist, discussed regional benchmarks for soil health.

    Attendees also heard from experienced growers Scott Park of Park Farming Organics and Andrew Brait of Full Belly Farm, who described how they assess soil health on their farms.

    By collaborating with others, Brodt said farmers and researchers are achieving benefits through learning together in real time. “We will also be able to benefit from aggregating soils data from across regions to begin to develop a statewide soil health database, which is a critical step in order for researchers to be able to determine relationships between farming practices and soil health outcomes under California conditions in the future,” she said.

    Lindsey Kelley discussed regional benchmarks for soil health.

    Slake tests can be performed on soil from one’s own backyard, garden or farm to better understand the health of the soil. Additionally, the NRCS principles of soil health – minimized disturbance, maximized biodiversity, maximized soil cover and maximized living roots – can be applied across all scales, though the specific practices will vary based on the type of yard or farm as well as the local climate and soil type.

    Brodt and Wauters, who coordinate the California Farm Demonstration Network, emphasize that it’s important to have local examples of innovative conservation practices across the state so people can see what is working to protect and enhance the soil health in their specific region. They encourage farmers and technical assistance providers to visit https://www.calfarmdemo.org/ to find local farms that are showcasing innovative practices. Farmers interested in being a farm demonstration site are also encouraged to contact Brodt (sbbrodt@ucanr.edu) and Wauters (vwauters@ucanr.edu).

    They hope to continue to support the learning and sharing of knowledge around climate-smart farming practices to help California’s farmers adopt climate beneficial practices.

    “CDFA has funding programs, such as their Healthy Soils grants, that farmers in our network can apply for to help cover the costs of implementing soil health practices,” Brodt said.

    Current work on the California Farm Demonstration Network is funded through a University of California Office of the President Climate Action Grant. — By Judith Eppele, UCANR

    UC Agriculture and Natural Resources brings UC information and practices to all 58 California counties. Through research and Cooperative Extension in agriculture, natural resources, economic growth, nutrition and youth development, our mission is to improve the lives of all Californians. Learn more at ucanr.edu and support our work at donate.ucanr.edu.

  • Can Whole Orchard Recycling Suppress Weed Establishment in New Orchards?

    Recent research has shown many potential benefits of utilizing whole orchard recycling (WOR) when removing an orchard. Instead of burning the wood produced in orchard removal, WOR involves chipping the wood from pulled trees and redistributing it back into the field using a chip or amendment spreader. This management technique has been mostly used in walnut orchards being followed by new walnut orchards. The conservation of the carbon in the wood benefits the soil by increasing nutrients available for the next crop, improving the soil’s water holding capacity and and enhancing microbial activity. After a recent evaluation of weed populations in a WOR trial in Yuba County, it appears that weed suppression in the first few years after orchard establishment at a WOR site may be yet another benefit to this practice.

    A WOR trial in Yuba County, led by UCCE Yuba-Sutter Farm Advisor Clarissa Reyes, was initiated by removing and chipping a mature walnut orchard at removal in late fall of 2023. The chips were spread at 60 tons/acre in winter 2023 in a grid design to allow comparison of orchard performance between areas with chips and areas without chips (control). RX1 rootstock trees were planted in April of 2024 and budded to Wolfskill walnuts in September 2024. In the first three months after orchard establishment, weed suppression was observed in the plots that had been covered in wood chips. Weed populations were surveyed in each plot in the orchard in August 2024.

    A representative three foot by twenty foot strip within the rows between two trees was evaluated for each plot within the trial. The percent of soil covered by weeds was estimated, and the dominant weed species were recorded. The plots treated with wood chips averaged 14% weed cover, while the control plots with no wood chips averaged 58% weed cover. This difference was significant and very visually apparent.

    In addition to difference in coverage of weeds, different species were observed in the chipped versus control plots. Almost all plots, regardless of treatment, had common knotweed (Polygonum arenastrum) and littleseed canarygrass (Phalaris minor). Control plots also had established populations of crabgrasses (Digitaria spp.), hairy fleabane (Conyza bonariensis) and fringed willowherb (Epilobium ciliatum). It is interesting that hairy fleabane, a particularly difficult weed to manage with known herbicide resistance, was suppressed in plots with chips. The possible mechanism of suppression for this particular weed could be physical, in that the seeds cannot germinate or seedlings are unable to break through the thick layer of mulched wood chips. Hairy fleabane has also been shown to be susceptible to allelopathy from juglone, produced by walnuts. There is no specific evidence indicating that the juglone in the soil from the wood chips is the control mechanism, but it may be worth evaluating in future trials.

    We expect that over time, the weed suppression will decrease and eventually there will be no difference between the chipped plots and the controls. However, reduced weed pressure in the critical first few years after orchard establishment may prove to be a valuable benefit to WOR. Annual weed surveys will continue in coming years of the Yuba County WOR trial. — By Becky Wheeler-Dykes, UCCE Glenn Orchard Systems & Weed Ecology Farm Advisor

  • What Are You Doing For Your Orchard’s Financial Longevity?

    Your prune orchard is an investment – the longer it remains a productive, high-yielding orchard the higher your return on that investment and the longer you can avoid the (very expensive) need for orchard removal, replanting, and years of non-bearing and low initial yields.

    Do you know what thiophanate-methyl is? It is the active ingredient in the fungicide Topsin-M. While this is not a pesticide advertisement or recommendation, research from the lab of Dr. Themis Michailides (UC Davis, based at Kearney Ag Research & Extension Center) has shown that Topsin-M is the most consistently effective fungicide for protecting fresh pruning wounds. Pruning wounds are very easily colonized by canker causing fungi (Cytospora, Botryosphaeria, and others). These fungi infect the fresh pruning cut with wind splashed spores during rainstorms.

    So, all you must do is prune, quickly clear the brush, and apply Topsin-M or another thiophanate-methyl product? Unfortunately, it’s not quite that simple. Although this fungicide is the best protective spray we have to-date, it significantly reduces but does not prevent all canker infections that can shorten your orchard’s lifespan. Still, to give your orchard the best shot at long sustained health and financial viability -integrate this spray in with other best practices:

    1. Skip pruning when you can (following a heavy crop, the year after detailed pruning, etc.), but make sure to shaker thin if a heavy crop sets because limb breakage is also an opportunity for canker infection.
    2. Prune around rain whenever possible. Early fall or after bloom are pruning timing options that may (should?) avoid rain. Never prune with rain in the forecast.
    3. Quickly push brush and consider spraying with a thiophanate-methyl product (Topsin®-M, etc.).
    4. Prune out and remove dead wood in the orchard to reduce canker inoculum. Burn pruning debris where permitted.

    *Note, Mention of any chemistries or trade names does not constitute a recommendation and are for informational purposes only. Always consult with your PCA before use and adhere to the pesticide label and local and state regulations.  — By Luke Milliron, UCCE Orchard Advisor Butte, Glenn & Tehama Counties, and Franz Niederholzer, UCCE Farm Advisor, Colusa, Sutter & Yuba Counties