Weather outlook The next 10 days will see consistent warm, dry weather in the San Joaqin Valley. Highs in the upper 70's to upper 80's and overnight lows in the mid to low 50's will allow steady thrips development, and we should see numbers starting to build up.
Generation peak timings since our last update a couple of weeks ago our predicted peak date for generation 3 has moved forward by one day to May 27th, and generation 4 has advanced by one day June 21st. If you are concerned about TSWV risk these are the two generations where control will have the biggest impact. Knocking thrips numbers down while the populations are still relatively small and while the crop is still small enough to allow good penetration of sprays is a good tactic. Keeping thrips under control at this stage also allows the crop to grow past the really vulnerable stage before and during flowering before there is much TSWV around and helps to reduce the yield impact if the virus does show up. The UC IPM guidelines for thrips control can be found by following this link. Further advice on treatments is available from your local UCCE adviser.
Resistance-breaking TSWV Strains of TSWV that can break the SW5 virus resistance in both processing and fresh market tomatoes have been found in Fresno county for the last couple of years. It would not be advisable to rely on this resistance to keep TSWV at bay, and a disease management plan should be followed to reduce the risk of yield loss. Contact your local UCCE farm adviser for more information.