Guido Schnabel (Clemson University) just provided his recommendations for the remainder of the season concerning strawberry disease spray programs. See the strawberry IPM guide at www.smallfruits.org to supplement this information (especially FRAC groups), but I concur with his thoughts as we move forward this season.
Guido writes. “In general, based on 8 years of testing, I recommend to primarily use multisites such as thiram and captan. Save the single sites (regular FRAC code numbers) for when you really need them. Use single sites when infection pressure increases (prior to major rain events (more than 24 hours of rain at mild temperatures). Do not use the same FRAC code twice in a row (resistance gets selected rapidly) and do not use the same FRAC code more than twice a season (if spread out enough 3 applications are okay too). Do not use FRAC1 and FRAC11 for Botrytis control (too many resistance issues). If you are using FRAC7/11 mixtures, I would recommend Merivon and Luna Sensation over Pristine. Pristine has been around for so long that the FRAC 7 component (boscalid) is loosing its efficacy. Switch and Miravis Prime contain fludioxonil (which is currently the heavy hitter of anthracnose and botrytis). Fludioxonil (FRAC 12) should also not be overused. Do not apply any product containing fludioxonil more than 2 to 3 times per season. That in a nutshell is my recommendation.”