Insecticide resistant cotton aphids, Aphis gosypii Glover, were indicated to be present in New Mexico cotton fields in 1991. Studies continued in 1992 indicated a lower level of resistance to some insecticides. Efficacy varied considerably in 1993 with Bidrin^®, Monitor^®, and Lannate^® being less effective, Thiodan^® with increased but ineffective efficacy, and Furadan^® being less effective. Furadan, Lannate, Lorsban^®, and Orthene^® were the most effective products. Various tank mixes with each other and with various pyrethroids were also effective at higher rates. The numbered compound TD-2231 40WP was not as effective at a rate of 1.13 pound (lb) formulation (form)/acre (a) as in 1992. Prentox^® PBO 8E used alone at 0.25 lb active ingredient (ai)/a was very effective, but did not significantly increase the effectiveness of Lorsban or Capture^® at the rates tested. CGA-25944 was slow acting, but gave 89% control by 6 days after treatment.

Sidedress application of Temik^® 15G in late season at 10 lb form/a resulted in the lowest accumulation of "aphid days" (1,318), and significantly (Pò0.05) increased lint yields. Yield benefits were also obtained with multiple applications of Bidrin in the same test which resulted in even lower (445) aphid days.