General situation
Temperatures remain close to historic normals, and are predicted to remain moderate for the next few weeks. Planting is progressing throughout the Sacramento Valley. I've started to see some early TSWV infections in March-planted fields in Yolo County.
Thrips population
We're heading into the second generation of thrips; egg hatch peaked last week, and adults are predicted to peak May 12th (Fig. 1). 3rd generation adults are predicted to peak in early June, and 4th generation in early July.
In typical years like this is shaping up to be so far, our normal recommendation is that if you don't know of any local sources of TSWV and crops are not in the ground or are just planted it might be worth delaying any treatment until mid-June. It would allow generation 3 adults to breed and lay eggs, but will catch juveniles developing from generation 3 eggs and suppress the spread of any TSWV that has come into crops with generation 3 adults. If you do have local sources of TSWV, or if you've planted early and are worried about early entry of TSWV to your crop, consider treatments in weeks 2 or 3 of May to suppress generation 3 thrips, which could be carrying TSWV.
During this important period for thrips management decisions (Generations 2-4), I'll be posting weekly updates to this blog. Please feel free to contact me (palazicki@ucanr.edu, 530-219-5198) if you have any questions.