Growing peach trees can be a trying practice due to the multitude of insects and diseases that injure or kill the tree, or make the fruit inedible. While there are some peach tree varieties resistant to pests, none are immune. Using a combination of a peach tree variety that works well in your area and is resistant to disease, along with planting them in an area with plenty of air circulation and sunshine, will help discourage pests and hopefully reduce an otherwise taxing spraying program.
Peach Tree Pests
Brown rot, peach scab, peach rust and peach leaf curl are all fungal diseases. Most of them overwinter in the bark or mummified fruit, and begin developing and infecting during warm, wet weather. Scale insects, plum curculio, peach twig borer, lesser peach tree borer, peach tree borer, catfacing insects and June bugs are insects that also tend to overwinter in the bark of the tree or in mummified fruit. As the days warm, they reproduce and spread. Their damage to fruits and the tree makes way for diseases.
Types of Sprays
Organic sprays include dormant oil for scale and fungus, copper and sulfur sprays for fungus, and neem oil for insects. Chemical sprays are innumerable, and great care must be used when choosing which to spray on your trees. Your local extension service will have a recommended spray schedule for stone fruit trees and recommended varieties of chemical pesticides that are currently considered safe by the Environmental Protection Agency. Since this list is regularly modified, it is important to keep in contact with your local extension service for updates.
Early Spray Regime
The spray regime varies from area to area, but this is an approximate time line. Dormant oil is applied once or twice during the dormant season to prevent scale-type insect infestations. Late-dormant applications of fungicide are made if late fall fungicides were not used. When flower petals begin to fall, apply insecticides to prevent borers and plum curculio, as well as fungicides to prevent scab. Repeat insect sprays every 14 days after bloom if there is a history of insect problems, and fungicide sprays as a preventative measure.
Harvest Time and Beyond
Insect and disease activity tends to intensify near harvest. For early producing varieties, spray insecticide and fungicides three weeks before expected harvest, then two weeks before, then three days before. For late producing varieties, spray two weeks before and three days before harvest. Remember that not all sprays are safe to use this close to harvest, so read the labels before applying. After harvest, soak the trunk from root to first scaffold with insecticide for borers, and apply fungicide if peach rust is a problem in your area. Fungicide applications continue through the dormant season.
Other Preventative Measures
Do not leave fruit on the ground or on the tree after harvest. Remove these and any tree cuttings entirely from the peach-tree area for disposal or composting (separate from the regular compost pile--the fungicides are detrimental to compost pile decomposition). Do not use this compost in the orchard, as the stones that will remain are still viable hosts. Select cultivars resistant to as many known pests in your area as possible. Resistant varieties (while not immune to pests) have a better chance of survival and productivity with spray programs.