Late season fungicides needed to protect against fruit rot in storage. Photo: K. Peter, Penn State
After seeing the apple fruit rot issues coming out of the cold storages from the 2016 season, I’ve been doing my best being a very broken record—preaching the need for keeping fruit protected until harvest. What happened last year? During the 2016 harvest, folks may have applied their last fungicide sprays late August or early September, only to be caught off guard by the high volume of rain we received during the month of September. Whatever had been applied prior to that rain was most likely washed off. Consequently, the fruit going into the cold storages were vulnerable.
It is critical to monitor your area for rainfall: If more than 2 inches of rain falls and you have already applied fungicides, another application will be needed to keep the rots at bay since there is a good chance the protection will have washed off. Moral of the story: you’re at Mother Nature’s mercy for when that final fungicide spray might be applied. Some nuggets of wisdom to keep in mind:
Not only a headache in the field, but the fungi causing fruit rots can be quite stealthy since spores will land on the fruit and cause symptoms only after the fruit have been in storage. This is especially significant if your apples are headed for a packinghouse or even fresh market.
I highly encourage growers to use Merivon (or Pristine) (FRAC Groups 7 + 11; 0-day PHI) or Luna Sensation (FRAC Groups 7 + 11; 14-day PHI) as their last one or two sprays before harvest since these products do show efficacy keeping rots in check while in storage. This recommendation is both for fresh market and juicing apples: the packhouses and processors will thank you! There are a couple of sprays up to that point, and the following are additional options for control (be mindful of the maximum limit for sprays for each product/FRAC Group):
- Flint (FRAC Group 11; 14-day PHI)
- Sovran (FRAC Group 11; 30-day PHI)
- Indar (FRAC Grop 3; 14-day PHI)
- Topsin M (FRAC Group 1; 1-day PHI)
- Captan (FRAC Group M4; 0-day PHI – used alone or tank mixed with a single mode of action product)
- Ziram (FRAC Group M3; 14-day PHI)
- Serenade Opti (biofungicide – B. subtilus; 0 PHI)
We evaluated Serenade Opti the last few seasons for summer disease control at 16 oz/A as the last two cover sprays, with a conventional program up to these sprays. We observed minimal fruit rot diseases in the field and storage, at least on Golden Delicious. These results may vary with other cultivars, depending on their susceptibility to certain rot diseases, as well as the severity of disease conditions.