- Author: Neil McRoberts
General Outlook
Post-winter thrips numbers are building up now. This week the second generation post-winter is projected to peak. Following the pattern of the last couple of years for May, TSWV incidence in the Merced area is still low this year which means that there is still an opportunity to get ahead of the disease by suppressing thrips numbers.
Projections and thrips management
The weather over the coming week is predicted to have highs in the mid 80s to low 90s F which means that thrips will be fully active. Generation 3 adult numbers are projected to peak in the next couple of days, with generation 4 on June 24. The build up in thrips numbers over the next 3 to 4 weeks will be very fast. For this reason suppressing these generations will be important to staying ahead of TSWV and avoiding economic damage in processing tomato. Any insecticide treatments planned for thrips control and TSWV management should be targeted at these two generations. Later treatments are likely to be much less effective. Immediate action is recommended.
Protection of sw-5 resistance
TSWV resistant varieties rely on the sw-5 resistance gene. The availability of effective TSWV resistance in processing tomato varieties is a huge bonus for the industry and a valuable shared resource that needs careful management. Growing sw-5 varieties without the benefit of insecticide protection to suppress thrips increases the chances of resistance-breaking strains of the TSWV virus developing. The larger the acerage of sw-5 varieties grown without insecticide protection, the greater the risk of resistance-breaking developing. For this reason, we strongly recommend that sw-5 varieties are treated like susceptible varieties and, if at all possible, you do not rely on the resistance alone to manage TSWV.