Population biology of and the impact of Araneae, on the blackmargined aphid and the yellow pecan aphid (Homoptera:Aphididae) in Texas

Abstract

Field studies were conducted at College Station, Texas in 1984-1986 to examine the population biology of the yellow pecan aphid complex. Populations of blackmargined aphids (M. caryella) were highly variable among pecan leaves. Leaves exposed to prior aphid feeding had fewer aphid-days than leaves in the control cages in early- and mid-season, but the reverse occurred in late-season. Blackmargined aphids were smaller as populations increased. There was no relationship between leaves exposed to heavy prolonged aphid feeding and water potential of the pecan tree. Studies on distribution of aphids on a pecan leaf cluster showed that yellow pecan aphids and blackmargined aphids reproduced and colonized their population on the younger and larger leaves better than the older and smaller leaves of the same cluster. Prior aphid feeding by either of these two aphid species caused the leaves to become less suitable for growth and development of the other aphid species. Thirty two genera from eleven families of spiders were collected from pecan trees, but only 16 genera from 5 families fed on blackmargined pecan aphids in nature. Spider feeding test's studies showed that generally a spider fed on more M. caryella under the laboratory conditions than under field conditions.