Welcome to the UC Davis Western Flower Thrips generation time projections for Kings County for 2015. The phenology clock is telling us that overwintering adults are present at this time.  Thrips degree-day accumulations are close to the 30 year average so far this year and we're projecting the peak dates for the first two post-winter adult generations at March 31st and May 8th.  Generally, TSWV doesn't begin to increase until the third and fourth generations of thrips are present. We'll be posting regular updates on the situation from now on.

General Situation Maximum temperatures over the coming week are forecast to be in the mid 90's F, which is ideal for thrips development.  TSWV has now been reported in all areas of the Central Valley, with some relatively heavily infected crops in northern Kings County.  Because of the relatively high disease pressure, a precautionary approach is recommended to avoid yield loss, particularly in late planted crops and varieties that do not carry the SW5 gene for TSWV resistance.

From now, through to the end of the cropping season, thrips generation peaks will be three to four weeks apart.  Crops which do not carry the SW5 gene for TSWV resistance should be protected until fruit set is complete, bearing in mind that a new wave of thrips adults which can spread the virus will build up and decline roughly on a three to four week cycle.

Generation 3 was projected to peak on May 23rd and will have produced eggs and a new generation of larvae.  Immediate spraying will reduce the number of these juveniles and reduce the numbers of adults in Generation 4.

Generation 4 is projected to peak on June 13th.  Adults from this generation will already be appearing.  Spraying between now will knock down the number of adults which are able to breed and lay the eggs which will give rise to generation 5.  Because there is some TSWV present in the region generations 4 and 5 adults will contain infected adult thrips that will spread the virus.  Concerted effort to reduce these generations will limit the effects of disease on late planted crops.

Generation 5 is projected to peak on July 4th.  This may be the last generation of thrips for 2014 that can cause serious damage to processing tomato because most crops should be past the very sensitive stage by that time. However, generation 6 is projected to peak on July 22nd.  Particularly on late planted and late developing crops, consider maintaining an active control program for thrips through to mid July.

General situation The situation remains unchanged since our last update on May 1st  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 next mini heat wave, due this week, 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.  to check generation 3 and delay further population build-up and TSWV spread you need to take immediate action.  If treatments cannot be scheduled before the peak in generation 3 adult numbers, consider treatment of generation 4.

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.

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.