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Captan Shortage (another option)

Feb 15, 2021 | Written by

There is another series of fungicide options that should also work for the cover sprays, and hopefully this will allow you to not use the DMIs in cover sprays. You could alternate SDHI (e.g. Miravis) and QoI (e.g. Abound) products as well, and this would give you more cover spray applications (four applications with two from each fungicide class) that would cover a goodly portion of the season — if wet conditions warrant their use. These products are highly active on scab and green fruit rot (brown rot on green fruit). Alternation of fungicides from different modes of action is also a good resistance management scheme, though slightly less effective than combinations based on scientific literature. However, practically, alternation can allow for resistance management while stretching out use of different fungicide classes over the season, whereas combinations can use up different classes in a shorter timeframe. There is always a greater risk of resistance development the more often you utilize classes that are prone to resistance (QoIs, SDHIs, or DMIs). Captan is not prone to resistance development, and replacing it with these other classes has to be addressed carefully this season. I hope that captan shipments will increase as the season progresses, and if available, it would still be the product of choice under wet conditions for cover sprays.

In case you have not figured it out yet, I really don’t like the DMI option for cover sprays due to resistance concerns and our generalized issues with DMI resistance a few years ago in Georgia. I really think DMIs should only be utilized after an application of a QoI/SDHI like Merivon or Pristine in the preharvest sprays; that is how I would use them anyway. Again, if you have to use DMI products in the cover sprays, I hope you can get by with that without priming resistance in one year. However, the DMIs are clearly my last choice for cover sprays, as we have had resistance before to that class. As far as I know, we have never confirmed Monilinia fructicola (brown rot) resistance to the QoI or SDHI classes, and I hope we never do.

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About Phil Brannen

Phil Brannen is a Professor in the Plant Pathology Department at the University of Georgia. He attended the University of Georgia for his undergraduate degree in Plant Protection and Pest Management, where he also received an M.S. in Plant Pathology, followed by a Ph.D. in Plant Pathology from Auburn University. He has extensive experience with disease management programs in numerous cropping systems. He serves as the extension fruit pathologist for Georgia – conducting research and technology transfer for multiple fruit commodities. His efforts are directed towards developing IPM practices to solve disease issues and technology transfer of disease-management methods to commercial fruit producers. He also teaches the graduate level Field Pathology Course, the History of Plant Diseases and their Impact on Human Societies Course, team-teaches the IPM Course, coordinates the Viticulture and Enology in the Mediterranean Region Course (Cortona, Italy), and guest lectures in numerous other courses throughout the year.