General situation
The oldest tomatoes have been in ground for more than a month, and planting is progressing rapidly. The warm weather in the past two weeks has pushed thrips population projections forward by a few days compared to the last report. 

Thrips population
First-generation adults are still feeding and laying their eggs; second generation egg hatch is predicted to peak next week. Generation 2 adults are predicted to peak in the second week of May.

The best window for spraying for thrips is in the third and fourth generations. The risk of earlier generations of thrips transmitting TSWV to the tomato crop is still relatively low. For newly hatched thrips to acquire TSWV, the larvae have to feed on an infected plant (Fig. 2). Only thrips that have acquired TSWV as larvae can spread it by feeding as adults. So at this point, any thrips which are carrying the virus likely acquired it by feeding on overwinter host weeds such as little mallow (cheeseweeds), mustards, and prickly lettuce. 

Promptly controlling these weeds in areas which have historically had high TSWV pressure reduces the likelihood of these early thrips generations acquiring the virus and spreading it to young tomato plants. 

Graphic courtesy of Diane Ullman