- (Public Value) UCANR: Safeguarding abundant and healthy food for all Californians
- Author: Mike Hsu
Salinas Valley lettuce growers lost about $150 million in 2022 due to diseases
A stormy winter could portend another devastating year for the lettuce industry in the Salinas Valley, which saw approximately $150 million in lost gross revenue in 2022 due to INSV (impatiens necrotic spot virus) and associated diseases. Recent drenching rains might mean more weeds – overwintering “reservoirs” for the tiny insect, the Western flower thrips, that carries INSV.
Or the extreme precipitation could benefit growers, as thrips in the soil – during their intermediate stage of development – might be drowned in the waterlogged fields.
As with so many aspects of the INSV crisis, the ultimate effects of flooded fields on thrips populations remain unknown.
“We don't know if thrips are just so persistent and so stable in that pupal stage that maybe they will emerge unaffected,” said Kirsten Pearsons, University of California Cooperative Extension integrated pest management farm advisor for Santa Cruz, Monterey and San Benito counties. “There's just so much about their biology and ecology in the Salinas Valley that we just don't know.”
The mystery of thrips, INSV and soilborne diseases (namely Pythium wilt) is why UC Agriculture and Natural Resources assigned Pearsons to the area last November and hired Yu-Chen Wang in October as UCCE plant pathology advisor for the three counties.
“They're stepping in at a critical moment,” said Richard Smith, the region's UCCE vegetable crop production and weed science advisor who retired in January after a 37-year career. “They've gotten grants funded already – and that's just incredible. They're hitting the ground running.”
Experienced in disease diagnosis and collaboration with growers and industry partners, Wang said her pathology background – paired with Pearsons' entomology expertise – will be crucial in addressing INSV and other diseases.
“It is important for Kirsten and me to work together and provide different insights for the vector and the pathogen, respectively,” Wang said.
‘It's going to take everything to get a crop'
One priority is untangling the dynamics of INSV and Pythium wilt co-occurrence – the subject of ongoing research by JP Dundore-Arias, a plant pathologist at California State University, Monterey Bay. While the vegetables may tolerate one disease or the other, their one-two punch often deals the lethal blow.
“The challenge is – which is why it's great to have Yu-Chen and Kirsten – is that we have so many problems now, whether it's Fusarium (wilt), or Verticillium (wilt), or Pythium, or INSV,” said Mark Mason, pest control adviser for Nature's Reward, which primarily grows lettuces on 5,000 acres across the Salinas Valley.
Mason said that co-infections on his crops (sometimes with three or four diagnosed diseases) make it difficult to assign monetary damages to a specific pathogen, but he noted he has seen fields with “100% loss.” According to the Grower-Shipper Association of Central California, about 11,500 acres were deemed not harvestable in 2022, representing 12% of lettuce industry acreage.
Given the gravity and complexity of the disease dilemma, Pearsons said she has been fielding calls from growers seeking new and better solutions – ways to improve existing tools, techniques borrowed from other crop systems, and additional biological or chemical means of control.
And although there are a couple of pesticides that manage the disease-carrying thrips reasonably well, growers and researchers are worried about their diminishing efficacy due to overuse. Plus, they only constitute a short-term fix.
“Managing the thrips will only reduce the amount of INSV that can get transmitted,” Pearsons explained. “You can kill 99.9% of the thrips, but you get one thrips that has INSV that enters a field, and now you have an infected lettuce plant. All of the thrips are going to come and they can spread it from there; pesticide slows things down, but it's not going to eliminate it.”
Finding disease-tolerant lettuce cultivars is a more sustainable approach. Trials conducted last year by Smith, Wang and others identified several varieties that appeared to hold up well to Pythium and INSV. While additional research could maximize their potential benefit, Wang said even the hardier cultivars will lose their resistance over time, and a multi-layered INSV strategy with “integrated management tools” is crucial.
“We realized, when this thing started happening, that we cannot spray our way out of this problem,” Mason said. “We need varieties; we need management practices; we need pesticides…it just seems like it's going to take everything to get a crop.”
Weeds key to disease control
An all-hands-on-deck approach helped control thrips-harboring weeds last winter. With fields drying out from January storms, Smith said communities must get back to weed management – with a focus on prominent weed hosts for INSV and neglected areas adjacent to farms. Hotspots of infection last year were traced to industrial lots that were overlooked during the weeding process.
“People can't lose sight of the fact that we still need to be controlling the weeds in key areas, because that's the reservoir of the virus during the winter,” Smith said. “We have to stay on task with that.”
Yet despite the diligent weed abatement, crop damage from INSV and Pythium was widespread in 2022, and Smith said it's “very possible” that high heat during the summer was a contributing factor to especially prevalent disease in fall. Thrips populations tend to thrive in warmer weather, Smith said, but much more research needs to be done to understand the basic biology of the insect, including how they acquire the virus and how they spread it.
High hopes for future
Pearsons cited the work of Daniel Hasegawa, a research entomologist with the U.S. Department of Agriculture, who leads teams in monitoring thrips populations in several locations across the Salinas Valley. Currently the counting of thrips on sticky card traps is done manually, but Pearsons and Mason mentioned the possibility of using AI and machine learning to expedite that process.
Mason said that the grower community is excited about the new technologies and ideas that Pearsons and Wang are bringing to the region. As a participant in the search for candidates to fill the advisor positions, Mason said “they were, in my opinion, by far the best fit for what we were looking for.”
“I hope they stay here for 30 years,” he added.
The new advisors both noted the palpable energy and cooperative spirit in the Salinas Valley to proactively meet the challenge.
“Looking to the past, there have been other outbreaks and diseases that they've managed to overcome,” Pearsons said. “These farmers are resilient and creative and I fully believe that lettuce will still be growing here for years to come – it might look a little different, and it might take a little bit of a painful period to get to that point, but I think that we're going to be able to come up with some solutions.”
And while there are concerns that some lettuce growers might decide to leave the region, Wang said she also believes in the industry's strong roots and rich history.
“Salinas Valley has had a beautiful climate for lettuce for so many years; there are some undeniable advantages here,” she said. “This is still the best place in the United States – and maybe the world – to grow lettuce.”/h3>/h3>/h3>/h3>
- Author: Cameron Zuber
- Author: Elizabeth J Fichtner
The removal of nuts remaining on almond trees from the prior year's crop is an important winter sanitation practice for the management of navel orangeworm (NOW), Amyelois transitella. Residual nuts are called ‘mummies' and the process of removing the mummies is referred to as a ‘mummy shake' because they are mechanically shaken from trees. This practice is conducted during the dormant and delayed dormant season, a time when orchard access may be thwarted by the winter rains.
Most growers strive to have the mummy shake complete by mid-January when buds are dormant and less likely to abscise from the vibration caused by a mechanical shaker. As the flower buds progress toward bloom, they become more sensitive to the shaker vibration and more likely to abscise. Studies conducted in the 1980s (Sibbett et al.) established that the shaking of mummies by January 31 (approximately 8 days prior to bloom) at a Kern County site did not adversely affect yield; however, the authors cautioned growers of the risk of delaying mummy shakes further, particularly on early blooming varieties and in locations in the southern San Joaquin Valley1. Because bud development and bloom date advance with increasing latitude, the potential risk of early and mid-February mummy shakes was investigated by W. Asai (Pomology Consulting, Turlock, CA) in the northern San Joaquin Valley. This work, conducted at a more northern latitude, suggested shakes conducted in early February may not compromise yield2.
The lack of yield detriment attributed to a mummy shake-mediated bud loss may seem counterintuitive; however, simple concepts of tree physiology may help explain this phenomenon. Consider that only approximately 30% of the flowers on a tree set a crop. A given tree does not have the carbohydrate stores needed to set every flower. As a result, the loss of a subset of flower buds may have little effect on overall yield. Naturally, the risk of crop loss increases the closer the shake approaches bloom, and both research groups suggested that mummy shakes be complete prior to the pink bud stage of development.
Although rainy years make it difficult for growers to access orchards and complete orchard sanitation tasks, the heightened soil moisture adversely affects NOW survival in comparison to dry winters. Mummy nuts on the ground support enhanced NOW survival on a dry orchard floor than on moist soil with winter vegetation in the row middles. The next step in managing overwintering populations of NOW is destruction of mummies by flailing or mowing. Flailing and mowing should be completed by March 1, prior to the emergence of NOW. The emergence profile of NOW varies by location, but the first flight generally starts in late March.
Growers who have not completed their winter sanitation practices by the end of January should walk their orchards to assess bud development in consideration of a delayed mummy shake. Winter sanitation can reduce now damage by up to 80%, so an early February shake may be worth the effort if orchard access is possible and bud development has not advanced into pink tip. For more information on NOW management, visit www.ipm.ucdavis.edu.
- Author: Trina Kleist, UC Davis
Invitan a agricultores a compartir sus experiencias y participar en un estudio
Un equipo multi estatal, encabezado por Patrick J. Brown, profesor asociado del Departamento de Ciencias de las Plantas de UC Davis, recibió 3.8 millones de dólares de National Institute of Food and Agriculture, USDA para mejorar la producción de pistache durante los próximos cuatro años.
La ayuda financiera llega en un tiempo de varios retos, cuando esa industria enfrenta inviernos más cálidos y escasez de agua. “Estamos en un punto único de la historia en el que podemos hacer esto”, señaló Brown.
El proyecto espera garantizar que la industria continúe prosperando, en las próximas décadas, a pesar de los retos a los que se enfrenta. Se invita a los agricultores a participar en el estudio, para que compartan su conocimiento y las prácticas agrícolas que ya están probando en sus propios campos y apoyen cualquier otro aspecto del proyecto. Para discutir cualquier posibilidad, póngase en contacto con Brown ya sea por correo electrónico a firstname.lastname@example.org o llamándole (530) 752-4288.
Este proyecto incluye investigación para garantizar la polinización, pruebas para calcular las necesidades de riego en caso de escasez de agua, implementación de herramientas para mejorar los programas públicos de reproducción de cultivos, desarrollo de equipos más eficientes para la cosecha y análisis económico para garantizar que en el futuro el cultivo de pistache continúe económicamente rentable. Los investigadores esperan ofrecer una guía a los agricultores para que puedan decidir si deben plantar nuevos huertos o eliminar algunos ya existentes.
“El éxito de la industria del pistache de California, como el principal productor de esas nueces en el mundo, siempre ha dependido de la fuerte colaboración entre los investigadores de UC y los productores de pistaches”, manifestó Florent Trouillas, especialista de Extensión Cooperativa en el Departamento de Patología de las Plantas de UC Davis y una de participantes en este proyecto. “Los esfuerzos de investigación deben continuar abordando los retos permanentes y los que están por venir, así como mejorar la sustentabilidad y asegurar la rentabilidad de los cultivos de pistache”.
Estas nueces verdes y sabrosas se han convertido en una industria de 5,200 millones de dólares en California, gracias a su gran tolerancia a los suelos secos y salinos. El proyecto tiene como objetivo mejorar aún más la adaptabilidad del pistache al cambio climático mediante la identificación de un portainjerto que pueda desarrollarse y florecer a pesar de la escasez de agua y la disminución, prevista en los próximos 50 años, de la calidad del agua. Con millones de árboles de pistache, genéticamente distintos que crecen en el estado, "Probablemente ya tenemos aquel que podría ser, próximamente, el mejor portainjertos de la industria", indicó Brown. "Ese ya existe en el campo de algunos agricultores. Solo hay que encontrarlo".
Los investigadores buscan combinar esos nuevos portainjertos con esquejes de alto rendimiento – la parte productora del árbol injertada en portainjertos – para desarrollar nuevas combinaciones que puedan florecer en las diferentes condiciones de todo el estado.
El problema cuando el “macho encuentra a la hembra”
Los pistaches, como muchos otros cultivos, cuentan con árboles machos y árboles hembras y requieren de cientos de horas de temperaturas invernales por debajo de los 45 grados Fahrenheit para que los árboles florezcan en la primavera. El viento esparce el polen de las flores masculinas en las flores femeninas, creando las nueces.
Las complicaciones del calendario: las flores machos y las flores hembras hembra suelen necesitar diferentes cantidades de frío invernal para florecer. Tras un invierno suficientemente frío, los machos y las hembras florecen juntos. Pero si el invierno es cálido, la mayoría florecerán en un tiempo diferente, lo que reducirá la polinización.
Eso paso en el invierno del 2014-15, cuando se registró un invierno inusualmente cálido y al siguiente otoño, los agricultores cosecharon solo la mitad del cultivo esperado, perdiendo más de mil millones de dólares, mencionó Brown. Además, se espera, que, con el cambio climático, haya progresivamente, inviernos más cálidos en el futuro.
Una complicación adicional: los esquejes machos provienen de una variedad o cultivar único y los esquejes hembras de otro cultivar único. "En California, parte del problema es que hemos estado dependiendo de un solo cultivar hembra", explicó Brown.
Una parte importante en este proyecto será poner a prueba nuevos esquejes que puedan polinizar efectivamente a pesar de los inviernos más cálidos. “Ahora contamos con nuevos esquejes machos y hembras producidos en los últimos diez a quince años, pero necesitamos más información sobre sus necesidades de frío”, agregó Brown.
La importancia del cultivo de pistache
Los pistaches son el cultivo de más rápido crecimiento en California, con alrededor de 520 mil acres plantados en 2021. Los agricultores han duplicado sus cultivos en la última década, debido a la tolerancia de los pistachos a las sequías y su mayor rendimiento comparado con otras nueces, según reportan expertos en la materia. California es líder en esta industria, toda vez que aquí se produce el 99 por ciento de los cultivos de todo el país y casi el 60 por ciento de los cultivos a nivel mundial. La producción de pistache da empleo, de tiempo completo, a 47 mil personas y en 2020 generó un total de 5,200 millones de dólares según la organización American Pistachio Growers.
Brown y su equipo de trabajo son parte de un esfuerzo más amplio en UC Davis para apoyar el crecimiento y adaptación del sector al cambio climático. Entre otros de los miembros que participan en este proyecto se incluyen a los codirectores Louise Ferguson, pomologista de Extensión Cooperativa de UC y Richard W. Michelmore, distinguido profesor y director del Centro Genome de UC Davis, Giulia Marino, especialista de Extensión Cooperativa y Grey Monroe, asistente de profesor.
Otros participantes de UC Davis son Trouillas y Brittney Goodrich, especialista de Extensión Cooperativa de UC en el Departamento de Agricultura y Economía de Recursos. El Proyecto también incluye a investigadores de UC Merced, New Mexico State University y Purdue University.
El proyecto de cuatro años se encuentra entre los subsidios de casi 70 millones de dólares de la Iniciativa de Investigación de Cultivos Especializados otorgadosen el otoño pasado por el Instituto Nacional para Alimentos y Agricultura. El Departamento de Ciencias de la Plantas obtuvo 3 de los 25 subsidios.
Editado para su publicación por Norma De la Vega
PROPOSED LABEL CHANGES
The US EPA has proposed a series of dramatic changes to rodenticide labels which will significantly change how rodenticides are used in alfalfa, pasture, and many other crops (orchardes, vineyards).
Among other restrictions,
- All rodenticides for field applications will be restricted-use (new requirements for equipment, training)
- Above-ground applications eliminated
- Within-burrow applications not allowed for first generation anti-coagulants during growing season
- Restrictions based upon the Endangered Species Act
These are substantial changes to the rodent management options for farmers.
The public has until February 13, 2023 to comment on these changes.
Pocket Gophers are a Major Pest in Alfalfa
How Important are Rodents as Agricultural Pests? Rodents cause substantial damage and health risks in agricultural productions systems. In alfalfa, rodents (primarily pocket gophers, meadow voles and ground squirrels) are major challenges, causing reduced yields, equipment damage and loss of plant stand. In other crops, damage may be through direct consumption of fruit, nuts, and vegetative material; damage to the plant (e.g., girdling of stems and trunks); by providing a food safety hazard from contamination; damage to irrigation infrastructure; damage to farm equipment; burrow systems posing a hazard to farm laborers; posing a health risk through potential disease transmission; and increased soil erosion by water channeling down burrow systems, among other potential damage outcomes.
Rodents also cause substantial damage and food contamination risks in livestock holding facilities, food processing facilities, barns, and other agricultural-related structures. As such, effective management is needed to minimize these risks. The use of rodenticides is often considered the most efficacious and cost-effective tool for managing rodent pests, and as such, it is often included in Integrated Pest Management (IPM) programs designed to mitigate rodent damage and health risks.
EPA Proposed Changes. Given the significance of rodenticides in managing rodent pests, it is important to know that the U.S. EPA has recently released a list of Proposed Interim Decisions (PIDs) for public comment that, if approved, will substantially alter if and how rodenticides may be used to manage rodent pests in the near future. As such, we felt it was important to inform California's agricultural producers as to the extent of these proposed changes, and if you are so inclined, we have provided a link for you to provide public comment on the PIDs, as well as links to contact your Senate and Congressional representatives to ensure your opinion is heard.
All rodenticides are currently under review. These include first-generation anticoagulants (FGARs; chlorophacinone, diphacinone, and warfarin), second-generation anticoagulants (SGARs; brodifacoum, bromadiolone, difethialone, and difenacoum), zinc phosphide, strychnine, bromethalin, and cholecalciferol. Of these, only FGARs, zinc phosphide, and strychnine have labels for use against field rodents (e.g., ground squirrels, pocket gophers, voles, rats, and mice found in agricultural fields), but not all of these active ingredients can be used for all rodent species. As always, it is imperative to fully read a rodenticide's label before determining if it is appropriate for use against a particular species and in a specific situation. That said, the following are some significant changes that have been proposed that you should be aware of. Other potential changes have been proposed as well, so please check out the PIDs for additional details (linked at the end of this document).
SIGNIFICANT CHANGES TO LABELS
- All rodenticides for field applications will become restricted-use products. This means that applicators will need to be certified to use restricted-use products in these settings. They will also have increased reporting requirements for their use.
- Aboveground applications would be eliminated in rangeland, pastureland, and fallow land. This is a substantial deviation, as many/most applications in these areas have traditionally been through broadcast applications or spot treatments. This change would leave only bait stations for ground squirrels and voles.
- Within-burrow applications of FGARs will generally not be allowed in croplands during the growing season. This would eliminate FGAR application for pocket gophers for much of the year, and would eliminate it for all uses in some crops (e.g., citrus and alfalfa in certain areas of the state).
- Carcass searches will be required every day or every two days (starting 3-4 days after the initial application), depending on the product used and where applied, for at least two weeks after the last application of the rodenticide. When carcasses are found, they must be disposed of properly. Any non-target mortalities must be reported to the U.S. EPA. Collectively, this will require a major increase in labor, potentially making rodenticide applications impractical in many settings.
- Extensive endangered species designations are anticipated that will limit or eliminate the potential to apply rodenticides. This could have large-scale impacts, although the full extent is not known at this time.
- New labels will require the use of a PF10 respirator and chemical resistant gloves during application. This is a substantial change for some rodenticide labels, requiring fit testing for all applicators, with the requirement of respirators ultimately making rodenticide application more physically challenging.
Additional details on these proposed changes can be found at the following websites:
- Anticoagulant PID: https://www.regulations.gov/document/EPA-HQ-OPP-2015-0778-0094
- Zinc phosphide PID: https://www.regulations.gov/document/EPA-HQ-OPP-2016-0140-0031
- Strychnine PID: https://www.regulations.gov/document/EPA-HQ-OPP-2015-0754-0025
- Bromethalin and cholecalciferol PID: https://www.regulations.gov/document/EPA-HQ-OPP-2016-0077-0024
Open for Comment - but not much time. As mentioned previously, these proposed changes are likely to have a substantial impact on the use of rodenticides in agricultural settings. However, these changes are currently open for public comment. If you would like to comment on these proposed changes, the required links and useful guidance can be found at the following website: https://responsiblerodenticides.org/.
You may also comment on these proposed changes to your Senate and Congressional representatives. If you are unsure who they are or how to contact them, check out: https://www.congress.gov/contact-us.
The deadline for making comments to the U.S. EPA is unfortunately short, with a final deadline of February 13, 2023. Therefore, you will need to provide your comments in short order.
- Author: Michael D Cahn
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Management of Soilborne Plant Pathogens with Organic Amendments
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Biology and Management of Thrips and the Diseases They Spread
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