Proper aphid species identification in apples can reduce grower concern. Throughout the United States, at least three different “green” aphid species overwinter in apples. The green apple aphid, Aphis pomi, may be the most common species, but the spirea aphid, Aphis spirecola, has become more numerous in key apple-producing regions. These two aphid species are nearly impossible to distinguish from each other based on external morphology and are often considered by growers and crop consultants as one pest. Researchers have determined that these species differ in their susceptibility to insecticides used to routinely control aphids. The wingless forms of these aphids are green, about three millimeters long with black cornicles (“tailpipes”), legs and antennal tips. The winged form has translucent wings, a black head and thorax, and is also about three millimeters long. One other commonly encountered green aphid in apple trees is the apple grain aphid, Rhopalosiphum fitchii. This aphid is most conspicuous on the swollen buds of apples early in the spring. The wingless form is yellowish green with a dark-green line running down the middle of the back and a few cross-lines running perpendicular to the center line. Unlike the previous species, the cornicles and legs are pale green. The apple grain aphid is not a concern as it rarely damages apple foliage or fruit and leaves apple trees for other summer hosts by apple bloom time. For young trees with lots of vigor and new growth, the presence of green apple or spirea aphid can cause concern especially in blocks with a prior history of aphid problems. These aphids can build up large populations in apples (and pears) rapidly in the spring. Aphid feeding can cause severe leaf curling, shoot deformation, stunted tree growth, reduced fruit set, and bumpy surfaces on fruit surface. Also, these aphids will produce copious amounts of honeydew. A black, sooty mold may colonize the honeydew on the surface of the fruit leading to surface discoloration or russeting and negatively impacting fruit quality. Commercial growers may routinely treat their apple blocks in the dormant and delayed-dormant tree stages with sprays of refined petroleum oils mixed with insecticides.

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