Location: Crop Improvement and Protection Research
Project Number: 2038-22000-020-032-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Apr 1, 2026
End Date: Mar 31, 2027
Objective:
The overall objective of the project is to enhance the knowledge of thrips and INSV, which has severely impacted lettuce in the Salinas Valley. Specific objectives include:
Objective 1: Deploy new surveillance traps to characterize thrips dispersal and risk for INSV infection.
Objective 2: Characterize INSV infections in weedy species.
Objective 3: Conduct thrips surveys in lettuce crops.
Approach:
Objective 1: Six to eight thrips traps will be deployed at various orientations and distances from lettuce fields prior to planting. Traps will be placed in transects that are upwind and downwind of each lettuce field at various distances. In-field farming activities will be documented, and thrips will be collected from the traps every 2-7 days to capture any responses in thrips populations to known in-field activities (e.g., thinning, weeding, insecticide applications, harvesting, etc.). Traps will remain at each field for the duration of the crop cycle. For each trap collection, thrips will be sorted and counted, and 10% of each collection will be tested as a single sample for INSV using RT-qPCR. If a sample tests positive for INSV, a follow up RT-qPCR test will be performed on a fixed number of thrips. This second test will quantify how much virus is associated with each thrips collection and will serve as a proxy of INSV risk associated with the population.
Objective 2: Seeds of weed species that were previously identified as INSV reservoirs will be propagated at the USDA-ARS in Salinas, CA. Western flower thrips reared in a colony at the USDA-ARS will be used to setup INSV acquisition assays using first instar larvae, followed by transmission assays using the adults. For each plant species, a single plant will be exposed to 10 viruliferous adult western flower thrips (5 male + 5 female) and allowed to feed for a 5-day inoculation access period (IAP). Thrips will be killed off, and the plants will be placed in a thrips-proof cage inside a greenhouse for up to six weeks. A minimum of three plants for each species will be inoculated, along with an equal number of uninoculated plants. Lettuce will also be included as positive controls. Symptoms of INSV infection will be recorded throughout the trial and at the end of the experiment, leaf and root tissue will be collected and tested for INSV using DAS-ELISA.
Objective 3: To gain a better understanding of the major thrips species that are associated with lettuce, thrips collected during the 2025 and 2026 seasons will be initially sorted at the genus level using a stereoscope and depending on the composition that is present within a sample. Up to 10 thrips per field will be slide mounted for species identification at the USDA-ARS.