- 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. The current risk in western San Joaquin county is lower than in other southern counties , but we think a precautionary approach is best. 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 28th. 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 22nd. Sprays applied in the 14 day period before this peak date will check generation 4 and delay further population build up and TSWV spread.
- 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 will peak around April 28th. 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 29th. Control of this generation would require pesticide application in the 2 weeks prior to this date; i.e. in the window from May 15th through 29th.
Generation 4 adults projected to peak on June 24th. Control of this generation would require pesticide application in the 2 weeks prior to this date; i.e. in the window from June 10th through 24th.
- 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 12th.
- Author: Neil McRoberts
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 southern Sacramento Valley and San Joaquin Valley. In the Yolo/Colusa area generation 3 adults are projected to peak today and generation 4 adults will peak around June 27th. TSWV incidence is still low so the the next 3 weeks are an ideal period for insecticide application if you are considering treatment for thrips/TSWV. Spraying at this time will reduce egg laying by generation 3 and will reduce generation 4 thrips.
Recently planted crops will be most at risk from spread of TSWV because the impact of the disease is greater the younger the plants are at the time of infection.
- Author: Neil McRoberts
The first generation of post-winter adult thrips were expected to peak (i.e. reach maximum size) on April 3rd. We are currently projecting that peak egg hatch for generation 2 will occur around April 24th. Generation 2 juveniles from that egg hatch will be the first opportunity for thrips feeding on tomato to acquire TSWV if there is any present. Given the very low levels of TSWV in planting material the risk of this happening is likely to be low. The recent period of unsettled weather will give way to more stable, warmer conditions next week with temperatures in the mid to high 70s. We can expect thrips activity to start to increase under these conditions. At this point in the season we are 3 days behind 2012 and the 30 year average for accumulation of thrips degree days, indicating that thrips activity is not likely to be above average in the early part of the season.
