Resistance of Aphis gossypii (Homoptera: Aphididae) to Insecticides in Hawaii: Spatial Patterns and Relation to Insecticide Use

For 16 populations of the cotton aphid, Aphis gossypii Glover, from Hawaii, comparisons of LC50s showed up to 3.6-fold resistance to endosulfan (an organochlorine), 390-fold resistance to esfenvalerate (a pyrethroid), 9.2-fold resistance to methomyl (a carbamate), and >2,000-fold resistance to oxydemeton-methyl (an organophosphate). Analysis of variance showed significant intra-island variation in susceptibility to each insecticide. Variation among islands was significant only for endosulfan. Total numbers of annual insecticide sprays per site ranged from 0 to 102. LC50s for endosulfan were positively correlated with the previous use of endosulfan; LC50s for oxydemeton-methyl were positively correlated with the previous use of organophosphates. Results suggest that variation in insecticide susceptibility was caused by local variations in insecticide use.