General situation

Above-average temperatures this week compensate for below-average temperatures last week, and thrips population projections remain similar to earlier predictions.

Thrips population

Generation 2 adult thrips are peaking now, and will be laying their eggs. Thrips population will be predominantly Gen 3 nymphs through the second half of May. Again--for growers considering treatment, if the field is high risk (in an area that has been heavily affected in the past or you are seeing early infections) spraying in the next few weeks could be beneficial. Otherwise waiting until Gen 4 may pay off in terms of investment in thrips control.

The resistance-breaking TSWV strain from Fresno has been detected in the northern counties since 2021, and last year another resistance-breaking strain was identified and appeared to be the dominant strain in Sutter and Colusa. I'm working with Bob Gilbertson's lab at UC Davis to understand more about the range and severity of these two strains. Feel free to contact me (530-219-5198; palazicki@ucdavis.edu) if you're seeing possible infections and would like confirmation.

Additionally, a reliable immunostrip test is available, which can be performed in the field to verify the presence of TSWV. The cost is $170 for a package of 25 test strips. https://orders.agdia.com/agdia-immunostrip-for-tswv-isk-39300