- Author: Neil McRoberts
General outlook We're heading into to a run of slightly warmer weather which will last about a week and accelerate thrips development. Although we haven't heard of any TSWV in Merced Co. so far, it has been reported in the southern San Joaquin Valley and the warm, dry winter may increase the risk of seeing disease early this season.
Thrips and TSWV situation The projection model is showing generation 2 egg hatch peaking right about now and adult numbers peaking at the end of the first week of May. Generation 3 adults are likely to peak in the first week to 10 days of June.
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 treatment until mid June. This would be our regular recommendation in typical years. 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.