California Ag Network

Tag: UCCE

  • Weather Conditions Cause of Rind Breakdown in Satsuma Mandarin

    Although you never know about the weather, we do know that if heavy rain occurs after color break in mandarins there can be significant rind breakdown. This problem can destroy much of the crop and the problem is largely preventable.

    Pre-harvest rind decay of mandarins in California generally occurs shortly after rain falls and is most severe on Satsuma mandarins. Although some researchers have associated the problem with fungi such as Alernaria species, isolations from affected fret have been inconsistent. Inoculations with isolated fungi only sometimes reproduce disease symptoms and only on water-soaked fruit. Furthermore, in preliminary field trials there were conducted in Butte Co in the fall of 2002 and 2003, fungicide treatments that included Topsin-M, Pristine and Abound only reduced the incidence of disease from 99% in the control to approximately 90% .  These data suggested that mandarin rind breakdown is a physiological, abiotic disorder of fruit rather than a pathological problem and the fungi isolated are rather secondary causes of rind decay than primary pathogens.

    Rind breakdown of citrus was previously reported by Fawcett and others in the 1930s. Wet weather combined with a sudden decrease in temperature was shown to result in generation of rind oil and collapse of cells just under the cuticle. In laboratory and field trials in 2003, fruit treatments with water repellants reduced the incidence of rind breakdown to very low levels. Field trials were again conducted in the fall of 2004. Fungicide treatments were ineffective in these trials. In all trials, application so Vapor-Gard or Omni oil significantly reduced the disorder. In all programs with Vapor-Gard and Omni oil, a first application was made at the end of October and there was no significant difference in efficacy when additions applications were done. When tree were protected from rainfall using a tent, the disorder could not be detected, indicating the rind breakdown is correlated to rainfall.

    In summary, results from the trials support previous findings by Fawcett that mandarin rind disorder is an abiotic, weather-related problem of mature fruit that has undergone a green to orange color change. Using a water repellant helps protect the fruit. — By Ben Faber, UCCE Ventura County Advisor

  • Students Gain Recognition for Research at California Weed Science Society Conference

    It’s 2022 and the California Weed Science Society was back in person at the Hyatt in Sacramento!

    It was touch and go leading up to the conference, but after it started everything seemed to go off without a hitch. There were lots of good exhibitors and a great lineup of speakers to listen to.

    My favorite part of the conference is the student presenters. This year we had a great turnout, with 5 graduate students participating in the oral contest, and 12 students in the poster contest (10 graduate, and 2 undergraduate).

    All of the students did an excellent job, making the final decisions by the judges quite difficult! Two independent judging panels compiled scores and delivered prizes. Below is a list of the Winners!!

    Undergraduate Poster Contest Winner

    First Place: Jennifer Valdez Herrera presented- Potential of Roller-Crimper Technology for Weed Suppression in Annual Crops. (Fresno State)

    Graduate Poster Contest Winners

    First Place: Wenzhuo Wu-The Comparative Flower development of Palmer Amaranth: Male vs. Female (Davis)

    Second Place: Sarah Marsh- Weed Control and Rice Response to Pyraclonil, A New Broad-Spectrum Herbicide in California Rice (Davis)

    Third Place: Aaron Becerra- Alvarez-Screening for Herbicide Resistant Weeds in California Rice Fields (Davis)

    Graduate Paper/Oral Winners

    First Place: Wenzhuo Wu-Sterile Pollen Technique as a Novel Weed Management Tool (Davis)

    Second Place: Liberty Galvin-Pre-emergent Oxyfluorfen Application to Control Weedy Rice in California (Davis)

    Third Place: Margaret Fernado-Impacts of Native and Introduced Cover Crops on Soil Health and Weed Populations in a Table Grape Vineyard of the San Joaquin Valley (Fresno State)

    I would like to thank all of the students who participated and attended the conference this year!

    If you know any students in weed science keep your eye out for the upcoming CWSS Scholarship program, and encourage them to participate in the contest at next year’s conference in Monterey! — By Thomas Getts, Weed Ecology & Cropping Systems Advisor, UCCE

  • Preparing Your Orchards for 2022 in the Face of Drought

    Plan for the worst, hope for the best. That’s a tough, solid, strategy as the 2021 season winds down and almond growers and PCAs look to 2022. The following are some considerations when following this strategy. Every operation is different, and growers must decide what works best for their business. Final decisions may not need to be made until early 2022, but planning ahead, given the stakes, is recommended.

    The core issue is water, with both availability and quality of concern depending on local conditions.

    The region and state start the water year (Oct-Sept) way behind on water. As of the middle of September, major reservoirs (Shasta and Oroville) serving the region and state are at 22-25% capacity, less than half of the normal storage for this time of year. The current forecast for the rest of 2021 is for equal chances for normal precipitation in the Sacramento Valley with a 70-80% chance of La Niña winter. 2020-21 was a La Niña winter. These are all predictions, not certainties, but the current precipitation outlook for the winter ‘21-‘22 is not great.

    If the drought continues, more groundwater will be pumped to keep trees alive and, if enough water is available, productive. Using moderate to low quality water (see table) can risk decreasing yield from increasing rootzone salinity and/or toxic levels of the elements chloride, boron or sodium. For most of the Sacramento Valley, groundwater quality is good to very good. However, for parts of the Colusa and Sutter groundwater basins, water quality is not so good. Irrigation water quality levels are important to planning for next year, especially if similar quality groundwater was used in 2021.

    Thresholds for 3 important irrigation water quality components based on risk to almond growth or yield reduction.

    *For a more extensive information on water quality for almond irrigation see:

    https://www.sacvalleyorchards.com/almonds/irrigation/lower-quality-water/ 

    With a worst case scenario of low/no surface water deliveries and falling well water levels, here are some thoughts to consider in planning for 2022.

    Rank orchards by potential value (net return to grower) in 2022 and future years. Possible considerations and rankings for use in farming decisions are suggested in the following table. These groupings are just examples based on UC research and the author’s experience. Orchard rankings and farming decisions should be based on local conditions and grower experience with input from PCA/CCA and nut handler.

    Orchard conditions possibly influencing net grower returns (NGR) in a drought year.

    Fall to prebloom practices can influence production potential for 2022 and could be adjusted on a per orchard basis. For example, higher cost items such as winter irrigation/salt management, potassium fertilization, preemergent herbicide and dormant sprays could be prioritized to the orchards with higher net return potential. [Orchard sanitation is also a big cost, but lack of sanitation in one orchard can mean that increased NOW, there, can spread harm and reduced net return in adjacent orchards.] Lower yielding orchards could receive less inputs this fall and/or spring, further limiting potential net income next year, depending on what is cut out or limited. Limiting inputs to orchards considered for removal could be further savings to growers.

    Hopefully, adequate rain and snow will mean that these hard choices to remove or limit orchard yield will not need to be made. In the meantime, planning ahead will make springtime decision making simpler if the weather stays dry. — By Franz Niederholzer, UCCE Farm Advisor, Colusa and Sutter/Yuba Counties

  • Vineyard Floor Management in Drought Years – Do Dust Mulches Help?

    During drought years, especially when irrigation water supplies are limited, conserving available soil water for vine water use is important. This paper focuses on management of vineyard middles to increase water availability to vines. For an excellent discussion of all aspects of vineyard management to conserve water resources see “Reducing vineyard water use: mechanisms, strategies, and limitations” by San Luis Obispo County UCCE Viticulture and Soils Advisor, Mark Battany.

    Seasonal considerations in California’s Mediterranean climate: In the fall and winter the presence of cover crops or resident vegetation on the vineyard floor helps to increase the infiltration of rainfall into soil. During these cooler months, the loss of soil moisture from evapotranspiration of the cover crop or resident vegetation is similar to the rate of evaporation from bare soil. Therefore, the presence of living plant cover during fall and winter is beneficial to the soil water balance.

    As vegetation continues to grow during warmer and drier spring months, the amount of evapotranspiration from the plant cover will begin to exceed that of evaporation from bare soil or soil covered with mulched plant material. Therefore, terminating plant cover in the spring with mowing, herbicide, or shallow tillage will conserve soil moisture. Plant mulch generated from chemical or mechanical mowing of vineyard vegetation will help to prevent evaporation from the soil surface, and greater plant mulch amounts will more effectively conserve moisture.

    Where little plant mulch is available, soil water loss can be further reduced by tillage, which disrupts soil structure and reduces the conduction of water from deeper in soil to the surface. In effect, tillage creates a soil mulch to slow evaporation. This approach is most often used in un-irrigated vineyards.

    The best tillage approach for water conservation: While tillage can preserve soil moisture, excessive tillage to create a “dust mulch” is not more effective in conserving soil moisture and can damage soil health and function, compared to reduced tillage. Researchers in the dry inland Pacific Northwest found that one pass tillage was equal to or better than creating a fine soil mulch for water conservation: “Conventional thought has been that it takes several passes to create an effective soil mulch, but our data shows this is not true. Soil does not need to be extensively tilled into fine particles to provide a barrier to evaporation.” Furthermore, they found that the cloddy, high residue surface created by a single tillage pass increased soil aggregation and water infiltration, reduced soil crusting, and increased the soil’s resistance to erosion compared to conventional tillage. 

    Soil health considerations: Excessive tillage is detrimental to soil health and can cause pollution. When soil has been pulverized, rainfall creates a surface crust that seals soil pores and increases surface water run-off. This not only reduces water infiltration into the soil profile, it can lead to erosion and sediment pollution of local surface waters. Loss of the surface soil layer, “topsoil”, where organic matter and nutrients are concentrated, reduces a soils capacity to support plants, which in turn reduces its ability to sequester carbon. Disruption of soil structure by tillage exposes protected organic matter to microbial decomposition. Eventually, this leads to reduced soil organic matter levels and microbial populations in soil. Because most soil carbon is found in soil organic matter, reductions in soil organic matter mean reductions in soil carbon sequestration. Soil organic matter also acts like a sponge, so reducing it shrinks the soil’s water-holding capacity. A final important consideration is the added expense and fuel use for additional tillage passes.

    The Bottom Line: When irrigation water availability is limited and conserving soil moisture is vital, terminate cover crops early and use minimal tillage to conserve soil moisture. “Dust mulch” is not more effective than minimum tillage and can harm long-term soil productivity and health. – By Erica Lundquist, Ph.D., CCA, Soil Conservationist NRCS Ukiah Field Office

    Editor’s Note: Photos courtesy of North Coast Soil Hub 

  • New Monitoring Tool for Navel Orangeworm in Mating Disrupted Orchards

    Traditional navel orangeworm monitoring tools have proven less effective in the presence of mating disruption technology in the orchard. Watch this brief video with UC IPM Advisor Jhalendra Rijal as he addresses the issue and shares about some new technology that can help growers more effectively monitor this tree nut pest.  Read more about it in Pacific Nut Producer Magazine.
    Please thank this video’s sponsor Trece for their industry support.

  • Managing Walnut Husk Fly in the Orchard

    Walnut growers should start monitoring for walnut husk fly in May.  Watch this video with emeritus UCCE IPM Specialist Bob Van Steenwyk as he provides timely step by step directions on how to monitor and manage this pest.  Read more about orchard pest management in Pacific Nut Producer Magazine.
    Please thank this video’s sponsor Trece for their industry support.

  • The Many Faces of Foxtails

    Hare barley in the spring, with fluffy spike seedheads.

    From roadsides in the city of Fresno to the oak woodlands in nearby Sequoia National Park, annual barleys and bromes are going to seed. In addition to a variety of other grasses, I often hear landowners, weed managers, pet owners, and veterinary advice blogs call these species “foxtails”. This common name is applied to so many species that if someone tells me they have a foxtail issue, I have to ask to see it so that I know what species we need to manage.

    Red brome after senescence in the spring, showing spiky seeds. These seeds, when found in animal fur, are often identified as “foxtails”.

    The term “foxtail” also means different things in different contexts*. In the veterinary context, the term “foxtail” typically describes a grass seed that has barbed awns that catch on animal hair and can cause serious injury, often affecting dogs. In the landscape context, the term “foxtail” typically refers to one of many grass species that produce a characteristic spike of awned seeds, and/or produces the kinds of seeds which hitch rides and cause injury in animals.

    Here I compiled a brief table of grasses commonly called “foxtails” (or their seeds are; in Fresno and Madera Counties):

    NOTE: This list is not comprehensive. There are many grass species in California that have seeds which can hitch a ride on livestock, clothing, and equipment. In addition, there are grass species (Setaria spp.) whose common name is actually “foxtail”, but they are uncommon in my counties and they are not typically associated with animal injuries.
    Mediterranean barley in the spring, showing a similar spike seedhead but is slightly bluer than hare barley.

    As you can see, many different species are commonly labeled “foxtails”. Most of them have the same impact to landscapes and animals: the grasses outcompete desired species, and they typically stick their awns in anything they touch. Livestock can carry the seeds in their hair, hide, or hooves, and avoid eating these grasses once the seedhead has developed, due to the barbed awns. People can find the seeds stuck in shoes, socks, and any other clothing, equipment, or pets that have somewhere for an awn to attach.

    While it’s fine to consider all of these species “foxtails” – the impact to you, your animals, or the landscape is similar, though not identical, across these grasses – it’s important to know what species you are dealing with before attempting any control methods.

    Medusahead in the summer, showing long, twisted awns on a seedhead that is otherwise similar to the annual barleys.

    Each species poses its own challenges and has different vulnerabilities. For instance, foxtail barley is the only perennial in my list; it will respond differently to management than the annual species. The bromes and annual barleys are winter annuals, sprouting in the fall and going to seed in spring. Medusahead can also sprout in the fall, but goes to seed later than the other annuals.

    For assistance identifying which kind of “foxtail” might be troubling you, I recommend checking out the Weed Research and Information Center (Weed RIC) resources on weeds by crop/topic or contacting your local farm advisor who can help with plant ID and management options. — By Rebecca Ozeran, Livestock & Natural Resources Advisor, UCCE

    *In a physical activity context, a foxtail is a toy where a ball has a fabric tail attached to it for throwing. Fortunately, this kind of foxtail doesn’t seem to be an invasive species unless you have a neighbor with poor aim.

  • Tarped Against Asian Citrus Psyllid

    Researchers at the California Data Analysis and Tactical Operations Center (DATOC) have analyzed Asian citrus psyllid (ACP) trapping data along major transportation routes before and after tarping regulations for bulk citrus shipments were enacted. The purpose was to determine the effectiveness of the policy.

    DATOC is an independent group of scientists sponsored by the Citrus Research Board and the California Citrus Pest and Disease Prevention Program. The group was formed in 2016 to create and amend tactical response plans for huanglongbing (HLB) suppression and management for California citrus.

    DATOC found a significant reduction in the rate of ACP finds throughout the San Joaquin Valley (SJV) after tarping regulations went into effect. The SJV contains more than 70% of California’s packinghouses. Coastal and Southern California counties ship more than 63 million pounds of bulk citrus into the SJV annually for processing.

    Source: Citrus Pest & Disease Prevention Program

    In years past, ACP populations have soared as they presumably “hitchhiked” on trucks that weren’t properly covered, coming from Southern California into the SJV and threatening the livelihood of commercial groves throughout California along the way. However, after the California Department of Food and Agriculture (CDFA) required tarping in 2017, DATOC data shows that tarping has effectively reduced ACP movement.

    While these results are encouraging, scientists say that growers must continue to remain vigilant. In a recent letter, Citrus Pest & Disease Prevention Committee (CPDPC) chairman Jim Gorden stated that ACP populations are expected to “flare up” occasionally, such as the late 2020 ACP detections in Kern, Madera, San Luis Obispo, Santa Barbara, Santa Clara, Tulare, Contra Costa and other counties.

    The CPDPC emphasizes that growers, packers, transporters and other stakeholders must continue to stay on top of this elusive ACP pest and the dangerous HLB disease it spreads. The upfront cost to manage ACP is much less than the potential hit to the citrus industry if HLB spreads throughout the state.

    In order to move bulk citrus from an ACP regional quarantine zone or a HLB quarantine area under the terms of the permit(s), growers, grove managers, haulers and harvesters must comply with the CDFA’s transporting requirement as detailed in their order. Get specific details here. — By Ben Faber, UCCE Advisor, Ventura & Santa Barbara Counties

  • New UCCE IPM advisor in Imperial County

    Apurba Barman joined UC Cooperative Extension as low desert integrated pest management advisor on Jan. 11, 2021. He will be headquartered at the UCCE Imperial County office, which adjoins the UC Desert Research and Extension Center in Holtville.

    “I am very excited for my new role as an IPM advisor based in Southern California and for the opportunity to serve one of the most important vegetable production regions in the state,” Barman said. “The diversity and intensity of crop production in this region demand targeted research to solve pest management issues and effective extension programs to reach diverse clientele. I feel prepared for this job with my experience and passion to serve the community.”

    Barman earned a bachelor’s degree at Assam Agricultural University in India, and master’s degrees in Indiana and at Texas Tech University, Lubbock. In 2011, he completed a doctorate degree at Texas A&M University in College Station, where he developed a research program to understand the extent of damage and management of thrips in the Texas High Plains region.

    Barman comes to UC Cooperative Extension from the University of Georgia, where he led a whitefly monitoring and management progress across cropping systems in the southern region the state.

    Barman can be reached at (209) 285-9810 and akbarman@ucanr.edu. His Twitter handle is @Ento_Barman.

  • Hive Strength and Bee Health/Safety for Successful Almond Crop

    For a successful harvest, start the season strong. A large crop at harvest requires good bee activity at bloom in the orchard. The current UC general recommendation for bee hive stocking rates is 1-3 strong hives per acre. A strong hive contains at least 8 frames covered with bees, an actively laying queen, and one to two frames of brood. Where cold, rainy and/or windy conditions limit bee flight (remember the 2019 bloom?), two to three strong hives may be needed to supply enough bees to set a decent crop when narrow windows of good bee weather open up. Less than two hives per acre may be sufficient to set a good crop in extended good bloom weather (2020 bloom). Good bee weather is at least 59oF, no rain and less than 10 mph wind speed. [In general, bees begin to forage when temperatures reach 55oF, winds less than 15 MPH and it’s not raining.]

    Hive strength makes a difference in pollination activity (see graph below). The more frames covered with bees in a hive means more foraging bees and more flowers pollinated. The best possible start to the season begins with strong hives in the orchard at the start of bloom. 

    Average pollen collected per hive for a range of hive strengths based on frames of bees per hive over a 7 or 10 day period. Data from Sheesley and Bernard, Cal Ag, 1970 

    To ensure strong hives in the orchard as bloom starts, pollination contracts should include 1) language stating hive strength and 2) an inspection clause stating that some fraction of the hives will be opened and frames inspected by a third party at or soon after delivery to confirm if the contracted hive strength was delivered. The hive strength check should happen at or close to delivery because, as almond flowers are an excellent food source for honeybees, a four-frame hive at delivery to the orchard can become stronger as the pollination season progresses. Assessing colony strength at the end or close to the end of pollination season is not an accurate measure of the pollination activity at the start of the season when strong hives are most needed.

    Growers using lower bee stocking rates (1-2 hives/acre) in an effort to save money are the most in need of contract language stating hive strength and a hive inspection. A single 8-frame hive collects 2.5x the pollen as a 4-frame hive.

    Hive health. Where hives are located and bees treated in an orchard can impact hive health and potentially pollination performance. Hive location, availability of clean water and spray programs (materials and timings) all should be considered by growers and communicated with beekeepers. Hive placement plays a role in good bee activity across the orchard. Hives should be placed in locations where early morning sun will warm the hives and in groups in or around the orchard no more than a quarter of a mile apart.

    Bees need water and will go find it (somewhere else) if not available in your orchard. Check-in with your beekeeper to decide on location and responsibility for providing watering stations for bees in your orchard. The water stations should be protected from pesticides by covering or moving the station or changing the water, or changing after spraying. Bees can’t drink while flying and can drown trying to get to water if there is no landing site at the water source. A 5 gallon bucket with clean water and an old towel or piece of burlap draped over the bucket lip and into the water works as a bee watering site. The Almond Board of California’s most recent Honey Bee Best Management Practices is available at almonds.com/sites/default/files/2020-12/BeeBPMs_12212020.pdf

    Bees can be harmed by pesticides. Certain pesticides and practices can be particularly harmful. In particular, all/any insecticides (except B.t. products such as Dipel) should not be used at bloom. Adjuvants, particularly organosilicones, can harm bees directly and/or increase the impact of pesticides on bees and should be left out of bloom sprays. Foliar nutrients may also harm bees. Protect your bee investment; put only fungicide(s) in the spray tank at bloom.

    While both bees and fungicides are needed during bloom in Sacramento Valley almond orchards in most years, the best practices for bee health and crop set require dividing the day between time for bee activity and time for spray activity; a split shift for bees and sprayers (on spray days). This approach lets bees work and then flowers can be protected. Here’s how that works.

    The key to good hive health is keeping sprays off the daily pollen load that forager bees carry back to the hive and fed to the brood. Almond flowers release some pollen every morning as humidity drops after sunrise. This occurs for several days after the flower opens. In an orchard with good bee activity, pollen released that morning is stripped from flowers by early afternoon. Fungicide spraying shouldn’t start until then; when pollen available for the day is gone (collected by bees and flown back to the hive). There are a couple of ways to check if the pollen is gone from flowers. If the pollen gathering bees (the ones with yellow lumps of pollen on their hind legs) are just doing touch-n-go landing on flowers, those flowers don’t have pollen left and it’s OK to spray. Another method is to rub the flower anthers (the spikey structures in the center of the flower) between your thumb and fingers and then check for yellow pollen on your hands. If there is little to no pollen on your fingers, the bees have been there and gone. (Wash your “pollen– check” fingers before rubbing your eyes. Don’t ask me how I know.)

    Almond flowers provide pollen (and nectar) that build strong hives while providing pollination leading to nut set and a good harvest for growers. The continued success of this annual win/win relationship relies on consideration of the needs of both partners. Growers need strong hives at the beginning of bloom and beekeepers need strong hives at the end of bloom.

    Finally, hives should be removed once 90% of the flowers in the last pollinizer variety have shed their pollen. By this time, the colonies have done their job in the orchard and most bees working the flowers will be foraging for nectar, not pollen. The majority of the pollen gathering bees will be foraging off-site and not providing pollination services to the grower who rented the hives. — By Franz Niederholzer, UCCE Farm Advisor, Colusa & Sutter/Yuba Counties