2025 Disease Update: Mitigating Brown Rot in Stone Fruit Orchards

Peaches and nectarines have started to ripen, which means 'tis the season for brown rot. Preharvest brown rot management should be underway, especially for varieties that will be harvested within the coming month. The fungus causing brown rot is quite opportunistic: it can kill blossoms and ruin the fruit you have worked hard all season to grow. Brown rot disease is favored by warm, wet weather conditions. We have had excellent conditions during June for latent brown rot spores to build up in the orchard. In contrast to the last several dry summers, the planets are aligning for this to be an ideal brown rot year.

Spores produced on early-maturing cultivars can fuel a continuing outbreak on late-maturing cultivars. To add another headache to the issue, insects can be important vectors of the fungal spores during fruit ripening: they can carry spores to injury sites produced by oriental fruit moth, Japanese beetle, green June beetle, and other insects that can injure fruit. Wounded fruit are much more susceptible to brown rot than unwounded fruit. It is critical to be on top of insect management. Keep in mind: under the right conditions, "healthy" fruit harvested can be contaminated and may decay later during storage.

This is a reminder of how to approach preharvest brown rot management. Research at Rutgers showed that applying sprays at 18, 9, and 1 day before harvest provided greater than 95 percent control of brown rot under heavy disease pressure. At Penn State FREC, we have slightly modified this preharvest spray regime to give a bit more wiggle room for growers, instead aiming for a 3-day window for each time point (21 – 18, 11 – 9, and 3 – 1 day before harvest). When following this regime, be sure to rotate chemistries by FRAC Group number for fungicide resistance management. For example, one could spray the following (provided the maximum number of sprays has not been exceeded for that chemistry):

21 - 18 day: Fontelis (FRAC Group 7; 0 day PHI)

11 - 9 day: Indar (FRAC Group 3; 0 day PHI)

3 - 1 day: Merivon (FRAC Groups 7 +11; 0 day PHI). 

Other options to rotate:

• Miravis (FRAC Group 7; 0 day PHI)
• Tesaris (FRAC Group 7; 0 day PHI)
• Luna Sensation (FRAC Groups 7 + 11; 1 day PHI)
• Luna Experience (FRAC Groups 7 + 3; 0 day PHI)
• Luna Flex (FRAC Groups 7 + 3; 0 day PHI)
• Pristine (FRAC Groups 7 + 11; 0 day PHI
• Topsin M (FRAC Group 1; 1 day PHI)
• Cevya (FRAC Group 3; 0 day PHI)
• Inspire Super (FRAC Groups 3 + 9; 2 day PHI)
• Tilt (FRAC Group 3; 0 day PHI)
• Quash (FRAC Group Code 3; 14 day PHI)
• Vangard (FRAC Group 9; 2 day PHI)
• Flint Extra (FRAC Group 11; 0 day PHI)
• Captan (FRAC Group M4; 0 day PHI)

These fungicides are not a complete list of what is available to manage brown rot on stone fruit. Be mindful of the products that were used to control blossom blight, and be sure to be in compliance by obtaining the current usage regulations and reading the product label. Depending on the number of sprays needed and what you may have used during bloom time, be sure to practice fungicide resistance management and rotate chemistries by FRAC group ("Spray by the Numbers"). The 2025 Guideline Chart for Fungicide Resistance in Peaches is available. If captan was sprayed during the cover sprays, tank mixing is not necessary during the preharvest period.

Organic options for brown rot management

The key for growers who farm organically or prefer using alternative products is to spray as often as possible as disease conditions persist, manage insects, scout often, and prompt removal of infected fruit as soon as you see it.  Spraying often ensures you have continuous protection; removing infected fruit from the trees ensures you are decreasing the number of spores available to cause disease and hopefully minimizing an epidemic. Dropping infected fruit to the ground will be enough to limit the spread. Vigilance is important, and this may translate to spraying every few days, especially if rain washes off products. According to studies at Rutgers, sulfur is considered a weaker fungicide for controlling brown rot; however, it is the strongest for organic management. Over the last several years, our field testing has shown efficacy for Serenade ASO, Double Nickel, and Oso. Copper is not effective for controlling brown rot.

Cherry Leaf Spot: Management needed postharvest

Even if your trees are free of cherry leaf spot, disease management is still necessary after harvest since conditions will continue to persist. Growers are encouraged to apply two postharvest fungicide applications to prevent cherry leaf spot infection.  The goal for the remainder of the season is to keep those leaves on the tart cherry trees and prevent premature defoliation due to cherry leaf spot infection. Tart cherry trees should not be "bald" in August.  This will stress trees, setting them up for a weakened condition as they enter the winter months.  Many options are available, such as Bravo, Topsin, Indar, Merivon, and Syllit (to name a few).

Additional Resources

Dr. Tree Fruit and Don Podcast

For commercial fruit growers, please note: When controlling for disease, weather, and tree growth conditions need to be monitored at a local level within one's own orchard. To assist with management decisions (especially infection events), growers can use the NEWA website, which has weather stations all over Pennsylvania.  Before chemical products are applied, be sure to comply with the current usage regulations and examine the product label. Product information can easily be obtained from CDMS, Agrian, or Greenbook.