Location: Crop Improvement and Protection Research
Project Number: 2038-22000-020-025-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Nov 1, 2024
End Date: Jun 30, 2027
Objective:
Lettuce production in the Salinas Valley is severely impacted by impatiens necrotic spot virus (INSV), a plant pathogen that is transmitted by western flower thrips. INSV can infect hundreds of plant species, including common weeds in the Salinas Valley. While weed management efforts are needed to break the disease cycle, non-crop vegetation provides critical ecosystem services in heavily managed areas (e.g., insectary habitat, erosion control). The goals of this proposal are to, 1) identify weedy sites that harbor INSV to prioritize weed management efforts, and 2) conduct INSV susceptibility tests on a panel of native and beneficial plants to identify species that are safe options to plant in managed areas. Outcomes include information on key areas to focus weed management efforts and a list of beneficial, non-crop plants with low INSV-risk. Success of the project will be measured by the number of stakeholders that have gained knowledge and adopted practices to reduce disease risk.
Approach:
Obj1: Field surveys to identify problematic areas to direct weed management efforts. Sampling will focus on 10 common weed species that have been identified as reservoirs for INSV. Sampling will occur during the winter and will focus on areas where INSV was the most prevalent in lettuce during the previous season. 5-10 sampling areas will be targeted, each area consisting of a ~.2-mile radius from the central location from where the INSV outbreaks occurred. From each area, ~40-100 individual plants will be sampled, and 800-1000 plants sampled during each period. Weeds will be sampled during 3 periods in Dec-Jan of 2024-2025, 2025-2026, and 2026-2027. Plants will be processed at USDA and tested for INSV using TAS-ELISA. Results will provide a percent infection rate for each of the weed species from each location.
Obj2: Conduct INSV susceptibility tests on CA native and beneficial plant species. Candidate plant species will be ranked based on their ability to provide one or more ecosystem service (erosion control, wind break, weed suppression, floral resource); prevalence in local native habitats or existing use in managed habitats; availability and affordability of seeds or transplants; drought tolerance; and maintenance requirements after establishment. INSV susceptibility tests will be performed on the top 30-50 plant species. For each species, plants will be sap inoculated with INSV in a greenhouse using established protocols at USDA. 3-5 plants of each species will be inoculated and monitored weekly for symptom development for 4 weeks. At 4 weeks, plants will be assigned an INSV severity score of 0-5 (0=no symptoms, 5=dead) and leaf and root tissue will be tested for INSV using TAS-ELISA. For plants that test negative for INSV, transmission studies using thrips from a colony at USDA will be conducted to confirm its infection status. A final info sheet including ratings for each species will be generated.
Obj3: Share knowledge with stakeholders. Obj1 outcomes will be immediately shared with respective landowners or parties with educational information about the biology and management of INSV. Obj2 info sheets will be distributed with stakeholders at meetings, webinars, blog posts, and trade journals. Outcomes will also be presented at professional meetings.
