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Just Peachy: ‘Tis The Season For Brown Rot

Posted: July 29, 2016

With peach season in full swing, a review of management strategies for controlling brown rot is discussed.
Protect peaches and nectarines from brown rot (Photo: K. Peter).

Protect peaches and nectarines from brown rot (Photo: K. Peter).

It has been quite a dry season for many in the region. This is in stark contrast to this time last year where folks were mowing their lawns every other day to prevent a jungle from growing. This year, it may have been last month the lawn was last mowed. However, some areas have been luckier than others when the rain clouds have come through.

Take Adams County, for instance: In Biglerville, tumbleweeds are rolling across the orchards, it’s so dry; however, seven miles down the road in Gettysburg, the corn fields look robust and all grassy areas are green. I still can’t quite figure out how we seem to miss just about every significant rainfall! The dry weather may slow down disease spread, but enough weather events have been occurring where we can’t rest on our laurels for disease management, especially for brown rot. For regions (Lancaster County) that have received a lot of rain, brown rot will be of significant concern. With peach season in full swing (for those who were not froze out in April), the following is a review of brown rot strategies to keep in mind:

Peaches and nectarines: A review of brown rot management strategies

Despite the dry weather, brown rot can still be an issue, especially when rain showers do occur. I’ve had the misfortune of grabbing a nectarine off the tree only to sink half my fingers into a sizable rotten part of the fruit, thanks to brown rot. Although we’ve barely received an inch of rain for the month at FREC, enough rain has fallen to keep the brown rot spores happy. The fungus causing brown rot is quite opportunistic: it can kill blossoms and it can also ruin the fruit you’ve worked hard all season to grow. Brown rot disease is favored by warm, wet weather conditions.

Under optimum temperature conditions, fruit infections can occur with only three hours of wetness when inoculum levels are high. Longer wet periods during infection result in shorter incubation times so symptoms develop more rapidly. It’s not uncommon to have brown rot appear “overnight” on fruit.

Spores produced on early maturing cultivars can fuel a continuing outbreak on late maturing cultivars – this is especially important for those who have battled rot infections already this season. 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’s critical to be on top of insect management. Another concern to worry about is split pit. There are a lot of reports of fruit with split pit this year. Unfortunately, these fruit are quite prone to rot problems. Keep in mind: under the right conditions, “healthy” fruit harvested can be contaminated and may decay later during storage.

Research at Rutgers has shown that timing brown rot sprays 18 days, 9 days, and 1 day before harvest provided greater than 95 percent control under heavy disease pressure. When following this regime, be sure to rotate chemistries by FRAC Group Code number for resistance management.

For example, one could spray the following:

(provided the maximum number of sprays has not been exceeded for that chemistry):

  • 18 days: Fontelis (FRAC Group 7; 0 day PHI)
  • 9 days: Indar (FRAC Group 3; 0 day PHI)
  • 1 day: Merivon (FRAC Group 7 +11; 0 day PHI).

Other options to rotate:

  • Luna Sensation (FRAC Group 7 + 11; 1 day PHI)
  • Luna Experience (FRAC Group 7 + 3; 0 day PHI)
  • Topsin M (FRAC Group 1) + Captan (1 day PHI)
  • Inspire Super (FRAC Groups 3 + 9; 2 day PHI)
  • Orius (FRAC Group 3; 0 day PHI)
  • Tilt/Orbit (FRAC Group 3; 0 day PHI)
  • Quash (FRAC Group Code 3; 14 day PHI)
  • Gem (FRAC Group 11; 0 day PHI)
  • Captan (FRAC Group M4; 0 day PHI)

Keeping in mind products that were used to control blossom blight, be sure to be in compliance by obtaining the current usage regulations and reading the product label.

Alternative options for rot management

The key for growers who farm organically or prefer using alternative products is:

  • spray as often as possible as disease conditions persist
  • manage insects
  • scout often
  • 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 amount of spores available to cause disease and hopefully minimizing an epidemic. Knocking infected fruit to the ground will be enough to limit spread. Vigilance is important and this may translate spraying every few days, especially if rain washes off products. According to studies at Rutgers, sulfur is not effective for controlling brown rot. Some organic options labeled for brown rot control are Cueva, Double Nickel, Serenade Optimum, and Regalia.

A reminder about using sulfur during hot weather to manage tree fruit diseases.

Sulfur is phytotoxic at high temperatures and should not be sprayed when temperatures at time of application or predicted for the next several days will exceed 85°F.

Resources:

Follow Penn State TreeFruit Doctor on Twitter (@drtreefruit)

for the latest up-to-the-second alerts!

For commercial growers:

For more resources, visit the Penn State Tree Fruit Production website.

For specific recommendations for disease management, visit The Disease Control Toolbox via the Tree Fruit Production website.

When controlling for disease, weather and tree growth conditions need to be monitored at a local level within one’s own orchard. Before chemical products are applied, be sure to be in compliance by obtaining the current usage regulations and examining the product label. Product information can be easily obtained from CDMS.

For the home gardener and backyard grower:

If you have questions about fruit trees growing in your backyard, please contact your county Extension office and ask for Master Gardeners:

Help can also be found at your local county Extension Office through the Master Gardener Program Hotline.

Useful information can be found in the guide for Fruit Production for the Home Gardener.

Contact Information

Kari A. Peter
  • Assistant Professor
Email:
Phone: 717-677-6116