Green peach aphids overwinter as wingless females and/or eggs underneath peach buds. Eggs hatch and young nymphs develop into stem mothers, which produce living young. Aphids have a high reproductive potential, although wind, rain, cold weather, and predators are important in regulating populations. After several generations of wingless adults, winged aphids appear during June, and all aphids leave peach trees during June and July to fly to alternate hosts. In the fall, aphids return to peach trees to overwinter.
The aphid is soft bodied, 1/16 inch long, and yellowish green. It is characteristically pear shaped with fairly long antennae and a pair of cornicles ("tailpipes") at the end of its body.
Aphids cause direct injury by extracting sap from plants. Toxins emitted by feeding aphids cause curling, distortion, occasional foliage discoloration, and premature leaf drop. Feeding aphids also excrete copious amounts of honeydew as a waste product, upon which grows a black, sooty fungus that causes smutting of leaves and fruit. Finding hundreds or thousands of aphids per plant is not uncommon.
Trees should be inspected weekly from petal fall until the terminals harden off. If more than two colonies per tree are found, an insecticide containing imidacloprid should be applied. Thorough coverage of lower leaf surfaces with an insecticide is necessary to control green peach aphid.