Peach Tree Diseases

Jeanne Grunert
Many garden pests cause peach tree diseases.

Peach tree diseases is a broad term used to describe problems affecting the tree itself and the fruit. Many peach tree diseases can be prevented by careful selection of cultivars, good gardening practices, and a maintenance schedule.

About Peach Tree Diseases

Nothing is as frustrating to home gardeners as watching all their hard work go to waste as their beloved peach trees struggle, the fruit turning brown and mummified. Peach tree diseases can be caused by microbes such as fungi and insects.

Common Diseases

There are several peach tree diseases caused by fungi. The diseases listed below are the major ones that attack peach trees, but there are many other fungal disease that can affect peaches. Spraying during the growing season and keeping the orchard swept of fallen fruit, leaves and twigs is the best way to prevent diseases.

Brown Rot

Brown rot causes the fruit to rot away on the tree. It starts as a brown spot on the peach itself, then spreads until it turns the entire fruit brown. Sometimes the fruit falls off the tree. It may also remain on the tree but whither and look dried out. Brown rot is caused by a fungus, Monilinia fructicola. The fungus lives in many temperature climates among other trees, leaves and more. It spreads by spores through the wind and loves moist climates, so you may notice this disease after a wet spring or a rainy season. This same fungus can also cause peach flowers to turn brown and fall off or new twigs to die off.

To prevent brown rot, always clean up rotted fruits. If the tree already has brown rot, it's very important to pick up and throw away the affected fruits, twigs and flowers. Don't compost them, since the fungus spores can live in compost, and if you spread the compost in the garden you'll only perpetuate the disease cycle. Use a fungicide such as Captan or an organic fungal spray according to package directions to prevent the disease. If you're planning a new peach orchard, make sure the trees are planted far enough apart to allow good air circulation and sunlight, which can reduce the spread of the fungus and keep the area dry, which prevents spores from developing.

Peach Scab

Like brown rot, scab is caused by a fungus, Cladosporium carpophilu. It's prevalent in the warm, moist, humid south but it can affect trees anywhere. This fungus causes brown spots on the peach fruit itself. Sometimes the fruit will crack, and rot may appear in the cracks. While scab won't affect the taste, they make it harder for the peach skins to slip off during the canning process, so if you plan to preserve the harvest avoid any fruits spotted with scab. To prevent scab, be sure to spray trees with a chemical or organic fungicide just as the blossoms fall off the trees and for about a month afterwards. That's when the fungus becomes active and infects the fruit. It actually starts growing when the fertilized flowers develop into peaches. Pruning, cleaning up fallen fruit and leaves from the orchard, and a rigorous regimen of spraying during fruit development will help prevent this disease.

Powdery Mildew

Powdery mildew, caused by a fungus called Sphaerotheca pannosa, affects garden plants as well as fruit trees. Leaves may fall off or they may develop abnormally. You can see a white fuzz growing on peach trees. While not a major problem for most home gardens, if powdery mildew strikes it can ruin the entire harvest. To prevent powdery mildew, the best practice is to buy cultivars (tree varieties) that aren't susceptible to the disease. Keeping the orchard area clean by raking up fallen leaves and fruit also helps, since the fungus over winters in garden debris. To find cultivars that will grow in your climate and are resistant to powdery mildew, talk to your local Cooperative Extension Office or garden center.

Insects

Insects can also chomp away at peach trees. There are numerous insects that attack peach trees. Japanese beetles are notorious for eating away the leaves. These beetles appear in June or July in most temperate climates and have a brown body a little smaller than a dime with a sort of iridescent green shimmer to the body. Sprays are the best way to prevent them from eating the tree leaves. They usually do not attack the fruit but they can weaken peach trees by eating away the leaves, reducing the tree's ability to make food through photosynthesis. Some horticulturists warn against Japanese beetle traps and claim that the pheromones, or chemical smells from the traps, actually attract more beetles than would normally visit the orchard. Hanging traps far away from the orchard to draw insects away may help keep them away from trees and avoid the attraction problem.

Other bugs that can attack peach trees or their fruit include mites, peach borer, and fruit moths which can all attack trees and fruit, causing disease-like symptoms. Some of these insect problems masquerade as fungal disease. If your peach tree looks sick, call your state or county Cooperative Extension Office and ask them if you can bring in a sample of the leaves or fruit. The experts there can help determine whether bacteria, fungi, or insects are the problem and recommend a course of action to preserve the tree. While you may lose the harvest, you can probably save the tree and hope that next year, the fates cooperate and you harvest a bumper crop of peaches

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Peach Tree Diseases