- Author: Neil McRoberts
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 4th. 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.
- Author: Neil McRoberts
General situation: The main season crop is in the ground and developing well as we head into high summer. The next 10 days is forecast to range from the high 70's to mid 90's, which is ideal conditions for thrips to develop.
Resistance breaking strains of TSWV: Resistance breaking (RB) strains of the virus have now been confirmed across the whole range of tomato production in the Central Valley so SW-5 varieties are no longer guaranteed to shrug off any early infections. After a few years of relatively simple TSWV management we're moving back into a period when a whole-system, IPM, approach will be needed to keep the virus at bay.
Thrips projections and management: We've extended the degree day model out to the end of July. Currently, the model is showing us that we're probably in the transition from the second to third post-winter generation. Generation 3 adults are peaking, with generation 4 adults following in about 3 weeks. These are the two key generations of thrips to control to prevent damage to the crop; growers who are considering investing in thrips control treatments are likely to see the biggest impact if treatments are applied any time from now through the end of June. We have had a few reports of scattered TSWV in crops and the aim now should be to stop thrips from spreading the virus from those few initial infections.