General situation  Welcome to our updates on Western Flower Thrips development for 2017. The cool wet winter and early spring mean that degree day accumulation for thrips is currently running behind the 30 year average.  The wet weather and saturated soils are also likely to have caused higher than normal mortality for thrips pupae, so we're expecting numbers to be low, at least to start with this season - but let us know if that's not what you're seeing!

Projected thrips development  As in previous years we're using January 1st as our start date for the biological calendar. Assuming that's approximately correct, the first post-winter generation of eggs probably hatched around March 12th and adult numbers will peak around April 9th.  Our current projection is showing generation 2 egg hatch around April 30th and generation 2 adults to peak around May 17th.  Generation 2 is the very earliest we would expect to see thrips starting to move TSWV around.  Again, let us know (through your local UCCE adviser) if you're seeing TSWV early in the season.

Resistance breaking TSWV Last season there were a number of confirmed cases of resistance-breaking(RB) strains of TSWV in mostly fresh-market tomatoes, but also in a processing tomato field, in the San Joaquin Valley.  The RB strains of the virus that can overcome (break) the resistance conferred by the SW-5 gene that is now widely used in fresh-market and processing varieties. Based on last season's observations the RB strain was quite localized (Cantua Creek, Firebaugh and Rt. 198), but we are keeping the situation under scrutiny and will be surveying crops this season to assess how things are developing.  We can report that we have detected the RB strain in weeds (sowthistle) with tomato spotted wilt symptoms from Cantua Creek and Rt. 198; thus, the RB strain has been able to survive the winter. We'll keep you posted on what we're seeing through these updates.  If you want to know more about the situation contact your local UCCE adviser.