VAMIDOTHION TOLERANCE IN A STRAIN OF THE WOOLLY APPLE APHID, ERIOSOMA-LANIGERUM (HAUSMANN) (HEMIPTERA, APHIDIDAE)

Two groups of apple trees were artificially infested with the woolly a pple aphid, Eriosoma lanigerum (Hausmann). One group was infested with a strain sensitive to vamidothion while the second group was infested with a strain thought to be resistant to this insecticide. Both group s were sprayed with vamidothion. There were initially fewer colonies o f E. lanigerum on the trees infested with the sensitive strain compare d with those with the resistant strain. After spraying there was a sig nificant reduction in the number of colonies on trees with the sensiti ve strain but not on those infested with the resistant strain. It ther efore appears that strains of E. lanigerum are at least tolerant to va midothion.