Biology of the Black Cherry Aphid in the Willamette Valley, Oregon

A study of the biology of the black cherry aphid ( Myzus cerasi (F.)) was made during the 1956 season. Although it was possible to control this aphid early in the spring, heavy reinfestations often developed during the late spring and early summer. During this study there was evidence of considerable movement of the winged summer migrants from one cherry tree to another to feed and reproduce. It was believed previously that these forms migrated directly to alternate host plants during the summer. These aphids were not found on alternate host plants in 1956, although observations in the present study indicated that no males were produced on cherry. It was estimated, on the basis of a field-rearing experiment covering part of the season, that a total of 12 generations, plus a partial 13th, were produced during the entire season. In the same experiment the developmental period, from birth to reproduction, ranged from 11.3 days in the 9th generation to 35.9 days in the 12th generation. The average number of nymphs per female per day ranged from 1.1 to 1.9. The following new predators and parasites were recorded: Hippodamia 5-signata ambigua Muls., Cycloneda polita Csy., Syrphus vitripennis Meigen, Ephedrus nitidus Gahan, Aphidius (Lysiphlebus) knowltoni Smith.