One generation is completed in two to three weeks. Adult aphids in a colony are generally wingless until crowded conditions induce the formation of winged individuals that can disperse to new hosts. The winged aphids often fly to a different plant species which is called the secondary host. By late-July, most of the rosy apple aphids have left the apple trees. The wasp egg hatches within the aphid and the young wasp larva consumes the aphid.
Parasitized aphids turn brown or black.
In time, the wasp larvae emerge as adults from the aphids, leaving behind empty aphid skins. These predators feed on many different aphid species in addition to other insect pests. A cool, wet spring favors aphid development because these conditions are unfavorable for the aphid's natural enemies. Varieties sensitive to rosy aphids should be sampled first. Chemical Control Good control depends on proper timing of insecticide applications.