Location: Crop Improvement and Protection Research
Project Number: 2038-22000-020-009-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Feb 1, 2022
End Date: Jan 31, 2025
In 2020 and 2021, two lettuce diseases caused by Impatiens Necrotic Spot Virus (INSV) and Pythium Wilt (PW) resulted in over $100 million in gross revenue losses. INSV is transmitted exclusively by western flower thrips, Frankliniella occidentalis, while PW is caused by the soilborne oomycete, Pythium uncinulatum. Co-occurrences of INSV and PW in 2020 and 2021 have caused much confusion, hindering the selection of appropriate management strategies. This project seeks to characterize the effect of INSV and PW co-infections under controlled conditions, to further understand the interplay between the two diseases and effects on plant health. The project also seeks to develop improved monitoring and detection tools for thrips and INSV. Outcomes from the project will provide improved surveillance tools and create knowledge that enhance the management of INSV and PW affecting lettuce in California.
Objective 1: Characterization of PW and INSV interactions in lettuce. Two separate greenhouse experiments will be conducted to assess the effects of INSV infection on lettuce susceptibility to PW, as well as the effect of temperature on co-infections. In the first experiment, plants will be inoculated with PW (soil), INSV (foliar sap), both, or neither. INSV inoculations will take place at three different stages of growth: 2-3, 5-6, 10-12 true leaves. In the second experiment, plants will be inoculated as described above (INSV at 2-3 true leaf stage), and plants will be maintained under two temperature regimes, 68/55F and 88/55F to mimic the high average temperatures for the spring and summer season. Above ground symptoms will be monitored throughout the experiment, while root symptoms, Pythium density in soil, INSV titers, and plant biomass will be recorded at harvest. Objective 2: Enhanced surveillance of thrips vectors. New molecular technologies will be explored to develop mass trapping and detection tools that identify thrips vectors that are vectoring INSV.