Southeastern Apple Production
ENTOMOLOGY
|
|
Southeastern Apple ProductionENTOMOLOGY |
|
Green apple aphid (GAA) and spirea aphid (SPA) are similar in appearance and behavior, and management for both species is the same. Hosts of GAA and SPA include apple, pear, quince, and hawthorne. These aphids may be abundant during the spring and early summer months, occuring mostly on young trees, water sprouts, and vigorous terminals. Unlike rosy apple aphids, these species remain on apple year-round.
Wingless aphids are a uniform green, except for the head, which is pale brown. Wings of the winged aphid are transparent. Eggs are glossy black and difficult to distinguish from eggs of the rosy apple aphid.
 Winged and wingless adults |
 Adults with eggs |
 Adults on leaf |
GAA and SPA overwinter as eggs on the bark of the previous season's growth, usually on rough areas such as leaf and pruning scars, spurs, or terminals. Eggs begin to hatch around the silver tip growth stage. These early spring nymphs, all females, are known as stem mothers. Stem mothers mature and feed on the opening buds and developing leaves, then give "birth" to living nymphs without mating (a process called parthenogenesis). These nymphs feed, mature, and produce living nymphs. Winged aphids (alates) eventually appear, and for the rest of the summer the population consists of winged and wingless parthenogenetic females that produce living nymphs. The winged aphids fly to other apples or other host plants and reproduce. In the fall, winged aphids produce nymphs that develop into true sexual forms. After mating with males, females lay overwintering eggs, which hatch the following spring.
Aphids suck sap from leaves, particularly near the growing tips. Heavy aphid feeding can cause curling and discoloration of developing foliage, and young trees may suffer reduced growth. The most extensive problems occur when high aphid populations develop on terminals and watersprouts and the area underneath becomes covered with honeydew. A sooty-mold fungus often develops on the honeydew, discoloring the fruit and lowering its quality. Aphids may also feed on immature apples, causing stunting and deformation, and on mature apples, causing russeting.
 GAA-infested shoot |
GAA and SPA are common apple pests. From the first cover spray through mid-July, sample 10 new shoots ('water sprouts') from each of 10 sample trees and record the number of terminals infested with one or more wingless aphids. Implement control measures when more than 50 percent are infested. Mature trees can usually tolerate high GAA/SPA populations without adversely affecting fruit quality or yield, but tighter control is more important on young trees.
Lady
beetles, syrphid flies,
and aphid
lions are important
biological control agents in helping to maintain aphid populations below
economically damaging levels.
 Lady beetle larvae feeding on GAA |
Insect and Mite Management Overview
Insect and Mite Index
Southeastern Apple Production
Mountain
Horticultural Crops Research & Extension
Center
455 Research Drive
Mills River, NC 28759
Phone: 828.684.3562 ~ Fax: 828.684.8715
Email: jim_walgenbach@ncsu.edu
Web Crafters: Anne S. Napier and
Steve Schoof
Email:
steve_schoof@ncsu.edu
Updated March 26, 2007