General situation Thrips numbers have increased rapidly in the southern arm of the Central Valley and TSWV has been reported in all of the areas we monitor.  There are numerous reports of  TSWV symptoms in crops from Stanislaus Co down to Fresno and Kings Co's, particularly around the Huron area. The current risk in Kings Co is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers. 

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 22nd.  Sprays applied in the 14 day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.  This means you need to take immediate action.

Generation 4 adults are projected to peak on June 14th.  Sprays applied in  the 14 day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

Welcome to the thrips population update service for 2014.

General situation Thrips populations seem to have come through the cold dry winter in high numbers and the warm spring is seeing the projected development rates for populations along the length of the Central Valley running ahead of the 30 year average.

Kings Co The first generation of post-winter thrips probably peaked in mid March.  Peak egg hatch for the second generation was predicted approximately a week ago and second generation adults will peak in the next 7 days.  These early generations of thrips are not a significant threat for spread of TSWV.  For growers considering an insecticide to reduce thrips/TSWV risk the generations to target are generations 3, 4 or perhaps 5.  For this part of the Valley, the current forecasts are:

Generation 3 adults projected to peak on May 23rd.  Control of this generation would require pesticide application in the 2 weeks prior to this date; i.e. in the window from May 11th through 23rd.

Generation 4 adults projected to peak on June 15th. Control of this generation would require pesticide application in the 2 weeks prior to this date; i.e. in the window from May 1st through 15th.

Harvest is now well underway and despite high numbers of thrips TSWV incidence remains low across the region.  Only late-planted crops are now at risk from serious yield loss from TSWV. Yield loss is worst when plants are infected before fruit set.  If any crops are still pre-set they should be considered as priorities when considering insecticide application over the next couple of weeks.  Generation 5 of the thrips is expected to reach peak hatch on July 26th and generation 6 will peak on August 14th.

Temperatures are predicted to peak at 100+ F at the end of this week before returning to the high 80s F early next week.  Thrips will develop rapidly under these conditions.

Thrips numbers are now high throughout the  San Joaquin Valley.  In the Kings Co. area generation 3 adults  peaked on June 1st and generation 4 adults will peak around June 20th.  TSWV incidence is still low so the the next 2 - 3 weeks are an ideal period for insecticide application if you are considering treatment for thrips/TSWV.   Spraying at this time will  reduce numbers of generation 4 thrips particularly and help to check the spread of any TSWV that is already present in fields.

Recently planted crops are at most risk from TSWV because thrips numbers are already high and the virus is most damaging when plants are infected while still young.