- Author: Richard Smith, UCCE Monterey
- Author: J.P. Dundore Arias, CSU Monterey Bay
- Author: Michael Cahn, UCCE Monterey
Pythium wilt of lettuce (Pythium uncinulatum) continued to be a significant production problem in lettuce fields in 2021. The levels of infection were not as extensive or severe as in 2020, but the damage caused by this disease was nonetheless problematic and serious in many fields. Pythium wilt was more frequently observed towards the end of the production season, and the development of noticeable foliar symptoms and severity of the disease appears to increase with higher temperatures. As an example, we observed growers successfully growing spring lettuce crops on blocks that were wiped out with Pythium wilt the prior fall, likely due to the lack of conducive conditions for the disease to develop. Given the rapid rise of Pythium wilt as a serious soilborne disease of lettuce in the Salinas Valley, there is a great need to better understand its biology and epidemiology to help determine the most promising means of managing it: cultural, chemical and/or varietal. In this write up we report on studies conducted in 2021 that included 1) evaluations of applications of fungicides and biologicals, 2) evaluation of effect of irrigation management on the incidence of the disease and 3) observations of varietal tolerance. Bottom line is that fungicides and biological control of Pythium wilt was measurable but limited in our studies. In the irrigation trials, we did not see higher incidence of Pythium wilt in the plots receiving greater quantities of irrigation water. There is good varietal tolerance to Pythium wilt in some commonly used lettuce varieties and to-date, this looks to be the most promising method for effectively reducing Pythium wilt losses.
Fungicide and Biologicals Evaluations: Twelve trials were conducted to test the efficacy of fungicides and biologicals for controlling Pythium wilt of lettuce. In ten trials, materials were applied over-the-top of the lettuce and incorporated into the soil by subsequent sprinkler irrigation applied within two days of application; in two trials, Ridomil Gold was injected into the drip system during an irrigation (see Table 1 for details). Top of the label rates of the fungicides and biologicals were used for each application to increase the chances of obtaining a signal from the materials. Fungicides tested in the over-the-top trials included Ridomil Gold, Previcur, Alliette and Ranman. Biologicals tested were Minuet (Bacillus subtilis) and LifeGuard (Bacillus mycoides). Over-the-top applications we made at-planting, thinning and/or at the rosette stage, but applications at each of these timings was not always possible in each trial and Table 1 shows the application timings for specific trials.
Planting dates for the trials ranged from June 12 to August 25. Trials were evaluated at or near harvest by counting all plants in each plot and then counting plants infected with Pythium wilt to get the percent infected plants. At times plots were also infected with Sclerotinia and a vascular wilt, and plants infected with these diseases were kept separate from the Pythium wilt totals. Trials planted before late July had levels of Pythium wilt that were too low to effectively evaluate (data not shown). However, trials planted in late July or after had greater incidence of disease. A confounding factor that affected the level of infection in later trials (Nos. 8, 9 and 10) was that by chance, the trials were located in fields planted with the green leaf variety Green Teen which appears to have significant tolerance to Pythium wilt and thus, these trials had little incidence of Pythium wilt (data not shown). Trial No. 7 provided the most useful data to evaluate the efficacy of over-the-top applications. The materials were applied at all three application timings and, on three evaluation dates, there was a trend indicating a lower percent of infected plants in each fungicide and biological treatment (Table 2). Although the trend was weak, it was consistent over each evaluation date. The data indicate a measurable but limited level of efficacy from over-the-top applications of these materials. Both Ridomil injection trials (Nos. 11 & 12) had significantly fewer infected plants in the Ridomil treated plots at harvest. Both fields had high levels of infection by Pythium wilt, and the reduction in infected plants was measurable but limited.
In summary, there was a modest level of control of Pythium wilt with the applied fungicides and biologicals. Injection into the drip system appeared more effective than over-the-top applications. It appears that evaluating a more effective means of applying fungicides and biologicals may be useful to see if better control may be achievable, especially in fields with history of high incidence of the diseases and during the fall lettuce crops when warm temperatures are expected. However, the challenge remains getting the material to move throughout the volume of soil occupied by the root system. This is important because infections with Pythium wilt can start on finer lateral roots or deeper in the soil and come up the tap root. Getting effective concentrations of a fungicide or biological material to the whole root system becomes a great challenge. Similarly, determining the right time of application requires further investigation.
Irrigation Evaluations: Pythium wilt is a water mold that can produce mobile spores. Excess water in the soil is thought to favor the development and spread of this organism. The goal of these trials was to evaluate if the volume of applied water might affect the incidence of Pythium wilt on lettuce. Four trials were conducted evaluating the impact of the amount of irrigation water applied during the crop cycle on the incidence of Pythium wilt. Trials were conducted in cooperating growers' fields. Irrigation regimes were established that compared 100% of crop ET (as calculated by CropManage) with 150 and 200% of crop ET. All trials were drip irrigated and the higher amounts of irrigation were applied in trials 1, 2 and 4 by using with separate manifolds equipped with a flow meter to measure the quantity of water applied. Trial 3 simply had two drip lines installed in the 200% ET treatment. At harvest, the plots were evaluated for the percent wilted plants (no. wilted plants/no. total plants). A sample of 10 plants from each plot was further evaluated to confirm if the cause of foliar wilting was Pythium wilt, Sclerotinia or a vascular wilt.
There were low levels of wilted plants in the first two trials (Table 3). In the later trials (3 & 4) there was significant wilting in the plots. However, there was no significant difference in the level of lettuce plants infected with Pythium wilt among the irrigation treatments in these trials.
Observations on Varietal Tolerance to Pythium Wilt:Formal variety trials were not conducted in 2021, but as opportunities to observe the response of varieties to Pythium wilt presented themselves, we made note of the level of infection in the varieties. One particularly dramatic example is shown in Table 4. At this site, there were two planting in which full beds (1 – 9 beds) of various varieties were planted in a field significantly infected with Pythium wilt. The percent of wilted plants in the different varieties, which ranged from 1.5 to 47.6% of total plants. The varieties Momentus and Copious had the lowest number of wilting plants and the lowest percent of Pythium infected plants, indicating good tolerance to this disease. In these two plantings, there were also plants infected with Sclerotinia and a vascular wilt resembling Fusarium wilt, though pathogen identity was not confirmed beyond visual observations. In some cases, it appeared that plants had both vascular wilt and Pythium wilt. These results indicate the co-occurrence of Pythium wilt and other soilborne diseases and raises the question whether they may interact while infecting a susceptible host. Clearly, more research is needed to better understand varietal tolerance of Pythium wilt and other associated soilborne diseases. In the end, varietal tolerance showed the greatest reduction in damage caused by Pythium wilt. The good news is that this tolerance is present in currently used breeding lines and hopefully can be quickly incorporated into other commonly used lettuce types.
Acknowledgements: We are grateful to the many cooperating growers and PCA's that helped us with these trials. We thank the California Leafy Greens Research Board for funding and thank the following research assistants for their help on these evaluations: Noemi Larios, Tom Lockhart, Tricia Love, Carlos Rodriguez Lopez and Yulissa Soto.
Table 1. Fungicide trial details. 
Table 2. Percent of plants infected with Pythium wilt on each evaluation date.
Table 3. Percent of wilted plants in each irrigation treatment and cause of wilting.
Table 4. Percent of wilted plants in each variety and cause of wilting.
Richard Smith, Farm Advisor
Daniel Geisseler, Professor of Nutrient Management at UC Davis has developed a tool for estimating the mineralization of nitrate-N from organic amendments. How much and when nitrate-nitrogen becomes available from organic amendments and fertilizers is difficult to know precisely. This tool provides estimates of mineralization of six materials. Soil temperature and moisture are critical drivers in mineralization of materials of specific carbon to nitrogen ratios. The tool provides mineralization estimates based on soil temperature data from local CIMIS weather stations, and soil moisture is assumed to be optimal near field capacity, as is the case in production fields with growing crops. The tool has an option to select rates of mineralization from the Salinas Valley. This tool will provide useful estimates for growers and crop consultants making decisions regarding nitrogen contributions from selected organic amendments to crops. Here is the link to the tool:
http://geisseler.ucdavis.edu/Amendment_Calculator.html
Here is an article by Daniel that explains some details regarding the scientific basis used for making the estimates in the tool.
Attached PDF for download or printing.
Organic Amendments Summary
- Author: Larry J Bettiga
Vístase Bien Para El Trabajo: Consulte El Nuevo Curso En Línea De UC IPM Sobre Equipo De Protección Personal (Dress Well for Work: Check Out UC IPM's New Online Course on Personal Protective Equipment)
Autor: Cheryl Reynolds y Petr Kosina
Si manipulas pesticidas como parte de tu trabajo, lo más probable es que usas algún tipo de equipo de protección personal (PPE). Sin embargo, ¿sabes si estás usando el tipo adecuado para el trabajo que haces? Usar el PPE apropiado, quitárselo de la manera correcta y limpiarlo correctamente evita la exposición innecesaria a pesticidas para ti y los demás. Conoce los pasos para no exponer a los miembros de tu familia o a quienes te rodean a residuos de pesticidas en la nueva versión del curso en línea sobre la Selección, Uso y Retiro Adecuados de Equipo de Protección Personaldel Programa estatal de IPM de la Universidad de California (UC IPM).
El curso tiene una duración de 1.5 horas y ha sido aprobado por el Departamento de Reglamentación de Pesticidas de California en la categoría de Leyes y Reglamentaciones (1.5 CEU). Este curso está diseñado para todos los manipuladores de pesticidas con el objetivo de proporcionarles información sobre las etiquetas de los pesticidas y el Código de Reglamentaciones de California (CCR) para ayudarlos a seleccionar, usar, quitar y almacenar o retirar el PPE. El curso está disponible de forma gratuita, pero aquellos que necesiten un certificado de CEU deberán pagar 60 dólares.
En California, todos los manipuladores de pesticidas (aplicadores, mezcladores, cargadores, los quienes transportan pesticidas o los quienes reparan el equipo de aplicación) tienen la obligación legal de usar PPE. Sin embargo, para obtener la mayor protección, el PPE debe usarse correctamente. Las violaciones que involucran el uso incorrecto de PPE fueron el segundo tipo de violación en el área agrícola más reportado en 2020 según lo informado por el DPR (https://www.cdpr.ca.gov/docs/license/pdf/pesticide_use_violation_2020.pdf).
El curso de PPE comienza con un escenario que describe un ejemplo real de un accidente reportado al DPR que condujo a un incidente de exposición a pesticidas porque no se usó la protección correcta para los ojos. El contenido que sigue está dividido en seis módulos, destacando los tipos de PPE, cómo seleccionarlos y cuándo deben usarse ciertos artículos. Vas a trabajar con las etiquetas de los pesticidas para aprender a seleccionar el PPE correcto y entender cuándo deben usarse ciertos artículos y responder preguntas breves sobre los diferentes tipos de EPP. Los videos instruccionales breves y las caricaturas animadas demuestran la manera correcta de ponerse o quitarse elementos como guantes, overoles, respiradores y anteojos. Para recibir su certificado de finalización y horas de educación continua deberás aprobar la prueba final con un 70% o más.
Si eres titular de una licencia o certificado del DPR y tu apellido comienza con las letras de la M a la Z, este es el año para renovar tu licencia. Ahora es un buen momento para tomar los cursos de capacitación en línea ofrecidos por UC IPM. Para obtener más información sobre la renovación de la licencia, visite la página web de DPR.
Algunas capturas de pantalla de este curso se muestran a continuación.
- Author: Michael D Cahn
- Author: Valerie Perez
CDFA's Healthy Soils Program (HSP) and the State Water Efficiency and Enhancement Program (SWEEP) are currently accepting applications! If you are an agricultural operation looking to save water and/or improve your soils then these programs might be for you. Below is a list of things to consider for the grants.
CDFA's State Water Efficiency and Enhancement Program (SWEEP): Apply for up to $200,000 for irrigation management practices that reduce water and greenhouse gas emissions (by conserving energy).
What is CDFA's SWEEP grant? CDFA's SWEEP provides grant funding to California agricultural operations to incentivize activities that reduce on-farm water use and reduce greenhouse gas (GHG) emissions from irrigation systems.
How is SWEEP funded? SWEEP is funded from the Budget Act of 2021 which allocated $50 million this round.
Who can apply? The irrigation project must be located on a California agricultural operation and cannot build upon previously funded SWEEP projects directly affecting the same Assessor's Parcel Numbers (APNs).
What are the exclusions from applying to SWEEP?
- You cannot apply to expand existing agricultural operations.
- You cannot apply to install new groundwater wells or increase well depth.
- You cannot test new technology or perform research.
Which practices are eligible for funding? Some of the practices that are eligible for funding are replacing pumps,v variable frequency drives, using soil moisture or plant sensors, converting to a more efficient irrigation method, or adding equipment for irrigating more efficiently such as pipes, flowmeters, and pressure regulators. CDFA is open to a variety of practice, including solar conversions, as long as the overall project will save water and reduce greenhouse gas emissions. The Request for Grant Applications has a sample list of practices on page i-iii (https://www.cdfa.ca.gov/oefi/sweep/docs/2021_SWEEP_RGA_-_October_19_Release.pdf).
How long is the project duration? The project duration is 24 months.
What information or documents do I need to apply?
- Pump efficiency test for all pumps that will be included in the project. The information you will need on the pump test is overall pumping efficiency percentage, horsepower, discharge pressure and pumping depth.
- 12 consecutive months of utility bills, actual fuel receipts and/or field operational logs.
- If applying for a solar project, you are required to get a quote from the solar company. All other projects are not required to have quotes, but it is highly recommended.
For more information please go to: https://www.cdfa.ca.gov/oefi/sweep/
Also Attend the CDFA hosted online workshop on Monday 11/15/2021 from 1-3pm.
Sign up for upcoming workshop here: https://us06web.zoom.us/webinar/register/WN_vIYKUkfOQbeUSsJ3ycVxpw
CDFA's Healthy Soils Program (HSP): https://www.cdfa.ca.gov/oefi/healthysoils/
Apply for up to $100,000 for soil practices that improve soil health and sequesters carbon.
What is CDFA's Healthy Soils Program? CDFA's Healthy Soils Incentives Program provides financial incentives to California growers and ranchers to implement agricultural management practices that sequester carbon, reduce atmospheric greenhouse gas emissions and improve soil health.
How is the Healthy Soils Program funded? The Healthy Soils Program is funded from the State's cap and trade also known as the California Climate Investments and the California Drought, Water, Parks, Climate, Coastal Protection and Outdoor Access for all Act of 2018. This round the Healthy Soils Program was appropriated $50.5 million.
Who can apply? California agricultural operations who will have control of the land during the duration of the grant can apply.
What are the exclusions from applying to the Healthy Soils Program?
- You cannot apply for practices other than those that are listed on the Request for Grant Application (https://www.cdfa.ca.gov/oefi/healthysoils/docs/2021_HSP_Incentives_RGA.pdf).
- You cannot apply for practices that you have implemented in the previous year.
- You cannot apply if the practices will be implemented in potted plants or other plant growth media.
Which practices are eligible for funding? Some of the practices that are eligible for funding are cover cropping, reduced-till, compost application and conservation plantings. The complete list of practice can be found on the Request for Grant Applications on pages 30-50 (https://www.cdfa.ca.gov/oefi/healthysoils/docs/2021_HSP_Incentives_RGA.pdf).
How long is the project duration? The project duration is three years long starting in 2022 and ending in 2025. Depending on the practice chosen, you will likely implement the practice once a year for three years.
What information or documents do I need to apply?
- A list of practices you wish to apply for, examples include cover crop, compost, hedgerow planting and mulch application.
- Information regarding the last three years of crop history and management practices. No documentation is required just a written statement.
- If you lease land, a statement signed from your landowner stating that you will have control over the land for the duration of the grant.
Attend the CDFA hosted online workshop for the healthy soils program on Thursday 11/18/2021 from 9-11am. The workshop agenda can be viewed here:
https://www.cdfa.ca.gov/oefi/healthysoils/docs/2021_HSP_Incentives_Workshop_Agenda.pdf
Sign up for upcoming workshop here: https://us06web.zoom.us/webinar/register/WN_p6Kxg55GTbSdXU5ddpsNGw
For FREE technical assistance in filling out the application please contact Valerie Perez, valperez@ucanr.edu or (831) 595-8545
For FREE technical assistance with equipment and irrigation system design ideas, please contact Michael Cahn, mdcahn@ucanr.edu or 831-214-3690
