Weeds in Orchards as Important Alternate Sources of Green Peach Aphids1 in Late Spring2

Abstract

As the population of green peach aphids (GPA), Myzus persicae (Sulzer), declined on peach trees, another population increased on lambsquarters, Chenopodium album L., and pigweed, Amaranthus retroflexus L., on the floor of the orchard. In 1973 and 1974 we estimated that roughly 3–16 million aphids/acre were produced on the floor of a peach orchard. The same weed hosts inspected 1–6 miles away from peach orchards indicated a substantial decrease in the number of GPA. However, a survey in the fruitgrowing area showed that apple orchards in proximity to peach orchards had as many GPA on the same weed hosts as in peach orchards. Orchard grass used as a ground cover will greatly minimize the number of suitable weed hosts of the GPA.