General situation: We're a little bit late getting the clock started this season, but here is the first post of the 2021 thrips/TSWV risk evaluation.  The aim is to give an update on a roughly 7-10 day interval until the end of June and then we'll take a look how the season is shaping up and most likely, reduce the frequency until harvest starts.
It's no secret that we've had another dry winter and spring.  There has been enough rain for the usual flush over-wintering weeds, some of which may act as sources for TSWV, but the soil has been dry enough that over-winter survival of thrips pupae was probably on the high side.  Overall, things are set up so that we could see relatively large thrips populations early in the season this year.

We finished last season with still no sign that SW5 resistance-breaking TSVW strains had migrated to, or emerged in, the mid San Joaquin Valley, so we're assuming that we're starting this season with no resistance breaking strains.  However, please keep an eye on any varieties carrying SW5 resistance and report any symptoms that might be TSWV to your UCCE local adviser so that we can stay on top of the situation.

Immediate outlook:  The first transplants in the region are either in the ground by now, or soon will be.  The first post-winter generation of adults peaked  3 or 4 days ago. The next peak in egg hatch is predicted for April 13th and the peak of the second generation of adults at the start of the first week in May.  Based on experience, we don't expect these two generations of thrips to be carrying much TSWV, but local hostspots could happen.  Based on temperatures so far this year, as far as thrips are concerned, Stanislaus County is a week behind 2020, 2 days ahead of 2019 and about 3 days ahead of the 30-yr norm.