Handout from VVA summer technical meeting

Most of us are about to see the end of critical time for berry infection by black rot, powdery mildew, and downy mildew.  Please keep up as much as you can with protection of vines for next few weeks.  I know many of us experienced some degree of flower and berry infection by either black rot or downy mildew due to frequent rain events, but once we pass the critical period (4-5 weeks after bloom for most of cultivars, and maybe 5-6 weeks for some susceptible varieties), these pathogen cannot cause disease on mature berries.

The next critical spray is for Botrytis at bunch closure and veraison.  Make sure to remember about rotation of mode of action groups as well as tank mixing.  Since many of Botrytis specific materials are prone to have fungicide resistance issue, it is better to mix with a broad spectrum material such as captan or copper.  (Mancozeb can be used too, but we are approaching to the 66-day PHI.) 

Another important IPM component for Botrytis management is the control of grape berry moth (or other insects or birds that can damage berries) and proper canopy management.  Although Botrytis is known to cause infection in relatively short amount of time (~4 hrs) in the lab setting, infection in the field often requires a lot longer wetness or high humidity event (15-17 hrs is often discussed as a threshold), thus, proper canopy management can have a very high impact on Botrytis management.

Also, here is a handout from VVA summer technical meeting, which covers results from recent fungicide trials, information on newer fungicides, management tips for major fungal diseases, etc.

We will see you tonight at Zephanirah!

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