Biology and Control of the Leaf Curl Plum Aphid in Northern California

Abstract

In 1953, the leaf curl plum aphid, Aphis helihcrysi Kalt., caused considerable damage to plums in the foothill areas of California. Biology and control studies were undertaken in 1954 and continued through 1957. The aphid, although having a very extensive host range, is closely associated with plum in California. It overwinters as an egg located between or behind the buds. The eggs hatch about the petal fall stage of the plums, and the stem mothers give rise to small green apterous forms which tightly curl the leaves. The aphids continue to reproduce within the curled leaves, infesting new growth until early June. At that time, alates are produced which leave the plums for an unknown alternate host. In late fall, alates return to the plums and give rise to small brown oviparae which mate and lay the overwintering eggs. Oil-dinitro treatments were effective in controlling the overwintering eggs, but injured some plum varieties. Oil-phosphate sprays at the delayed dormant stage also controlled the eggs and did not injure the trees. With the exception of Thimet, no phosphate tested gave control of the aphids once they were within the curled leaves.