General situation with apologies to everyone, we're a little late getting underway this season - a combination of a family health emergency and international travel to an epidemiology workshop.  Temperatures will start rising from tomorrow morning, peaking in the low 80sF on Thursday before settling into a run of days where the maximum will be in the mid 70's, with no rain on the forecast.

Thrips development The degree day model is showing that Generation 2 peak egg hatch will be occurring this week.  Based on that, and the 30 year temperature accumulation curve for this time of year, the peak adult activity from that hatch would be expected around May 6th.  Knocking Generation 2 back would be the earliest intervention that would be likely to have an impact on TSWV spread, but it might be more effective to hold off until Generation 3 is active.  The decision will depend on a few other circumstances.  Consider targeting Generation 2 if: the location of the crop has a history of TSWV; you are already seeing thrips on sticky cards; there are early reports of TSWV in the area. If thrips numbers remain low and other risk factors are not indicating high risk, consider waiting until Generation 3 before investing in control.  Generation 3 adults are projected to peak in the first week of June, so treatments scheduled in the last week of May would be appropriate. We will update the dates in response to the weather over the next 4 weeks.

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 70's to 80F, reaching the mid 80's by the first few days of June.  Planting has been happening rapidly over the last 2-3 weeks and crops will pull away quickly with settled warm conditions.

Thrips and TSWV So far, thrips numbers have been low and we are not hearing reports of TSWV so far in this area  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 14 and Generation 4 adults will peak around July 7.  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 the San Joaquin Valley, 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.