Cool-Season Cover Crops in the Pecan Orchard Understory: Effects on Coccinellidae (Coleoptera) and Pecan Aphids (Homoptera: Aphididae)

In mature pecan orchards under minimal or commercial management, cool-season understory cover crops of hairy vetch, Vicia villosa Roth, and rye, Secale cereale (L.), sustained significantly higher densities of aphidophagous lady beetles than did unmown resident vegetation or mowed grasses and weeds. In cover-cropped understories, mean densities of aphidophagous coccinellids were nearly 6 times greater than in unmown resident vegetation and approximately 87 times greater than in mown grasses and weeds. During late winter and spring, rye harbored abundant bird cherry-oat aphid, Rhopalosiphum padi L., whereas hairy vetch sustained pea aphid, Acyrthosiphon pisum (Harris); blue alfalfa aphid, A. kondoi Shinji; and thrips, Frankliniella spp. The following aphidophagous lady beetles were abundant in cover-cropped understories: (1) convergent lady beetle, Hippodamia convergens Guerin-Meneville; (2) Olla v-nigrum (Mulsant); and (3) seven-spotted lady beetle, Coccinella septempunctata L. In the orchard under minimal management, there was evidence that the rye/vetch mixture led to enhanced densities of convergent lady beetle in the pecan trees. However, no other effects on coccinellids were seen. There was no evidence of improved biological control of pecan aphids. (C) 1991 Academic Press, Inc.