Location: Crop Improvement and Protection Research
Project Number: 2038-22000-018-016-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2021
End Date: Sep 30, 2022
In 2019 and 2020, lettuce production in the Salinas Valley was severely impacted by the insect-borne pathogen, Impatiens necrotic spot virus (INSV). INSV is transmitted by the Western flower thrips, Frankliniella occidentalis, a prolific pest with an extensive host range that includes numerous crops that are part of a diverse cropping system within the Salinas Valley. There is a need to understand how adjacent non-lettuce crops and habitats may impact the occurrence of INSV outbreaks in lettuce. Specifically, identifying sources of thrips populations that are vectoring INSV remains the most crucial, as these populations pose the greatest threat to lettuce production because of their ability to transmit the virus. Information regarding the seasonal and non-seasonal sources of thrips vectors across a landscape is critically important for improving management strategies, as demonstrated for other insect vectors in California, such as beet leaf hopper and Asian citrus psyllid.
Intensive sampling of thrips populations will be conducted throughout the Salinas Valley. Sampling will occur in major non-lettuce crops that are often grown in rotation with or adjacent to lettuce, including broccoli, cauliflower, strawberry, spinach, and artichokes. Habitats will also be sampled for thrips, including the east and west hillsides of the Salinas Valley and riparian zones along the Salinas River. Thrips will be collected, preserved in alcohol, and brought back to the lab at USDA-ARS in Salinas for further testing. Thrips will be counted, and RNA will be extracted. To determine the INSV infection status for each population of thrips, a subset of the sample will be tested using RT-qPCR. Thrips populations that are positive for the virus will then be assigned an INSV risk index score based on an equation using values obtained from the test. Thrips sampling will take place during the lettuce and non-lettuce growing seasons.