Green Peach Aphid
Resurgence of this aphid on peaches following sprays of broad-spectrum foliar insecticides is attributed to the destruction of natural predators and to insecticide resistance.
Description and life cycle
The green peach aphid is recognized by three longitudinal dark green stripes on the pale green body. This species has a complex life cycle, with five distinct morphological forms and two different behavioral forms. Its primary host and overwintering source is peach trees. 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. After several generations of wingless adults, winged aphids appear during June, and all aphids leave peach trees during June and July. These migrant aphids do not affect peaches because they infest other crops and weeds. Large numbers of green peach aphids may develop on weeds in the ground cover of peach orchards. Aphids return in the fall to peach trees to overwinter.
Monitoring and management
Trees should be inspected weekly from petal fall until the terminals harden off. For nectarines the treatment threshold is one colony per tree, and for peaches the threshold is five or more colonies per tree. Large trees can tolerate higher levels of infestation. Currently available insecticides provide excellent control of green peach aphid. Neonicotinoid compounds (e.g., Assail, Calypso, Provado, Actara) or Movento are the most effective insecticides; thorough coverage of lower leaf surfaces is necessary. Predators such as syrphid fly larvae and ladybird beetles often contribute to biological control of this aphid.
The green peach aphid is a known vector of the quarantine stone fruit disease plum pox (Sharka), which was recently identified in some south-central Pennsylvania peach and nectarine orchards. Plum pox disease is one of the most devastating diseases of stone fruit in Europe. For more information, see the Special Section: Plum Pox (p. 145).