General Situation After the wet winter and extended cool spring, the annual summer weather pattern finally seems to have established itself. Temperatures for the next 10 days will see daily maximum values in the mid to high 80's, reaching the low 90's by the first few days of June. Based on drive-by observations in the Davis-Dixon-Vacaville-Woodland area a lot of crop has gone into the ground in the last couple of weeks. The warm weather will allow those crops to get away quickly, but will also accelerate the rate of thrips development.
Thrips and TSWV So far, thrips numbers have been low and we are not hearing reports of TSWV so far in northern counties. This is all good, but we are concerned that the late planting times will mean that the pre-flowiering high risk period for TSWV will be extended this year. We are predicting that Generation 3 adults will peak around June 12 and Generation 4 adults will peak around July 5. Given the slow start and low leves of TSWV so far, unless there is a local source of TSWV, Generation 4 seems the more likely source for any significant chance for TSWV to spread around, and the more likely to pay off in terms of investment in thrips control. Contact your local UCCE adviser if you want to discuss options specific to your situation.
Resistance breaking TSWV Remember reistance breaking strains of TSWV are now widespread in northern counties, so varieties carrying the SW-5 resistance won't necessarily stand up on their own without thrips management if there are local sources of TSWV. At locations with a history of TSWV it's probably better to treat SW-5 varieties the same way as varieties without the resistance gene.