An Ecological Study of Aphids 1 on Strawberry in Southern California

Abstract

Population growth trends of aphids and their natural enemies were studied on a summer planting of ‘Torrey’ variety and a winter planting of ‘Sequoia’ variety strawberries in southern California. Leaflets were sampled at weekly intervals from Sept. 21, 1967, through June 25, 1968, from a summer planting and from Dec. 3, 1968, through June 24, 1969, from a winter planting. The melon aphid, Aphis gossypii Glover; potato aphid, Macrosiphum euphorbiae (Thomas); and the strawberry aphid, Chaetosiphon frogaefolii (Cockerell) were the most common species present, with the strawberry aphid the most abundant, especially during the spring months. The braconid Lysiphlebus testaceipes (Cresson) was the most common primary parasite reared from aphid mummies, and Alloxysta bakeri (Kieffer) and Asaphes sp. were the two most numerous hyperparasites. Altogether, 4 primary and 8 secondary parasites were reared from the 3 species of aphids. The pathogenic fungus Entomophthora planchoniana Cornu was a primary mortality factor affecting the aphid populations, especially the strawberry aphid.