Although green peach aphids are not always a serious problem every year, this could be one of those seasons that are favorable for their growth, and the colonies of greenish, smooth-looking aphids can start showing up in peach blocks around this time. They cause curled leaves that may turn yellow or red in severe cases. Green peach aphids suck the sap from the new fruits and twigs, and are also found on plum, apricot, cherry, and many ornamental shrubs. Also, keep an eye out for black cherry aphid in your cherry trees after shuck fall. By midway through the growing season, the majority of leaves are hardened off and psylla development then may be limited primarily to the water sprouts.
Honeydew injury occurs when excess honeydew drips onto and congregates on lower leaves and fruit.
The honeydew is a good medium for sooty mold growth. When it occurs on the fruit, it russets the skin and makes the fruit unsaleable. However, to obtain commercially acceptable fruit in New York, pear psylla generally must be controlled with insecticides. For psylla control, we have historically recommended an application of an effective insecticide when nymphs start to build to the level of 1-2 per leaf after petal fall. More than one application of some material is often necessary.