First Symptoms of Apple Bitter Rot in 2022 Visible in Winchester, VA
First signs of bitter rot disease on fruit of apple cultivar ‘Golden Delicious’ have been found on 12 July in Winchester at AREC’s experimental Block 30 (Fig.1). Rot started from the fruit side (Fig. 1). We found that bitter rot lesions were almost always on fruit in dense clusters with many fruit together indicating on the conducive moisture in these clusters and lack of fungicide coverage on fruit penetrating in between the fruit (Fig. 1 ). Bitter rot fungi can infect any fungicide-uncovered areas on fruit, especially when warm wetting events occur, and we had more than several of these in the last 30 days. Extreme heat and the rain that “came” back this week have and will extremely favor this disease in the weeks preceding harvest. Start scouting for bitter rot symptoms to make sure your trees are free of this disease and to determine sure how good was your fungicide coverage during the early summer cover sprays. We hope you will NOT see any bitter rot in your blocks and that your fungicide coverage was satisfactory. However, if you see bitter rot on some fruit, especially on highly valuable crop like ‘Honeycrisp’, our recommendation is to protect the whole block by immediately spray applying the full rate of captan plus higher rate of Pristine or Merivon or other QoI containing fungicides such as Flint Extra, Luna Sensation or similar. We would also recommend to include a surfactant such as LI-700 to enhance fruit coverage (use low rate for coverage only!). This will help both to inactivate spores on the decay lesions and to protect the remaining healthy fruit from infection until they can be harvested. We warn that if fruit will be sold for pick-your-own, then the full rate of captan close to harvest may be a problem and one might get by with a half-rate of Captan 80 plus a full rate of either Pristine or Merivon (read the labels and PHI limits of these fungicides). After harvest, strive to pick all of the decayed fruit from the the orchard floor before winter and destroy it by burying the fruit. If the bitter rot affected block was a block that had fire blight last year or this year, it will also be important to cut out and remove all of the dead fire blight wood because bitter rot likes to colonize old fire blight strikes.