Why Do Peaches Not Ripen on Trees?

Insects

• Two major pests of peaches contribute to fruit not ripening on trees: the plum curculio and the oriental fruit moth. The plum curculio is a small beetle that feeds on peach fruit as soon as it appears on the tree. The beetle feeds on the flesh near the peach pit and burrows within the fruit to lay eggs. Symptoms of plum curculio infestation consist of small entry wounds in developing fruit, premature fruit drop during the early summer and fruit that does not ripen on trees. The oriental fruit moth is a devastating pest for apple and peach fruits. The moth larvae burrow into peach terminal shoots and peach fruit. Symptoms of infestation consist of small holes in the fruit, fruit drop, black spots on peach skin and fruit not ripening on trees. However, you may not notice fruit holes from the borers until the fruit is cut open because of small entry wounds.

Maintenance

• Peach trees require regular fertilization, full sunlight and regular pruning to produce healthy, ripe fruit. They prefer an even spread of 10-10-10 fertilizer, which consists of 10 parts nitrogen, 10 parts phosphorus and 10 parts potassium. Apply fertilizer during the early spring for mature trees and every 40 days for recently planted trees. Peach trees require full sunlight for fruit production and growth. Prune dead branches to increase sunlight and vigor. Increasing sunlight can help peaches ripen on the tree.

Disease

• Brown rot and scab are two fungal diseases of peach trees that affect fruit production. Brown rot is a serious disease, caused by the fungus Monilinia fructicola. Symptoms of infection consist of flower wilt, brown blossoms, mummified fruit, fruit drop and fruit that do not ripen. The fungus favors wet conditions and open wounds in fruit for infections. Scab is another serious disease of peach fruit that causes stunted growth, small dark green spots on fruit skin, premature fruit drop and fruit cracking. The fungus favors tree moisture and temperatures of 65 to 75 degrees Fahrenheit.

Control

• Spray insecticides before petals fall and as soon as peaches appear on the tree to control and prevent plum curculio beetles and the oriental fruit moth. Remove and destroy infected fruits to prevent brown rot from spreading to noninfected peaches. Alternately, chemical fungicides are effective for preventing infection. Increase air circulation by pruning dead branches to prevent peach scab, and destroy infected branches and fruit to control scab. However, damage is superficial and rarely warrants chemical control.