- Author: Neil McRoberts
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 including Merced County so 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 21st 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 and June 13th 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 may well 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 5th. Depending in crop development, 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. Particularly on late planted and late developing crops, consider maintaining an active control program for thrips through to mid July.
- Author: Neil McRoberts
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 reports of TSWV symptoms in crops from Stanislaus Co down to Fresno and Kings Co's., although the incidence is sporadic. The current risk in the Merced area is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. Another mini heat wave 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 21st, one day earlier than in our last update. Sprays applied immediately will check generation 3 and delay further population build-up and TSWV spread.
Generation 4 adults are projected to peak on June 16th. 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.
- Author: Neil McRoberts
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. The current risk in the Merced area 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.
Generation 4 adults are projected to peak on June 16th. 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.
- Author: Neil McRoberts
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.
Fresno 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 is peaking right now. 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 5. For this part of the Valley, the current forecasts are:
Generation 3 adults projected to peak on May 21st. Control of this generation would require pesticide application in the 2 weeks prior to this date; i.e. in the window from May 7th through 21st.
Generation 4 adults projected to peak on June 19th. Control of this generation would require pesticide application in the 2 weeks prior to this date; i.e. in the window from June 5th through June 19th.
- Author: Neil McRoberts
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 in the next day or so and generation 6 will peak on August 13th.
