Effect of Lorsban, Dowco 214, and Xrd 473 on Pyrethroid Resistant Tobacco Budworms, 1989

Formulated insecticides were evaluated for toxicity to tobacco budworms in the laboratory by application to cotton terminals (cv. ‘STV 213’ ) in water pics using a laboratory spray table. Tobacco budworms used in these tests were obtained from a cotton field near Glen Allan, MS, which had experienced cypermethrin control failure in 1986. Two budworm cultures were established on artificial diet: a 4 × resistant culture maintained in the laboratory without further cypermethrin exposure, and an 18 × resistant culture which was established from the original 4X resistant line by cypermethrin application pressure in the laboratory over 12 generations. Resistance levels were determined by topical bioassays of larvae. The spray table was calibrated to deliver 6 gal/acre at 2 mph with 30 psi at one TS6 nozzle. Each treatment consisted of 3 replicates of 20 terminals/replicate. Controls were treated with water only. One 3rd instar tobacco budworm was placed on each terminal 30 min after spraying and held under ventilated cups at 85 F and 55-60% RH. Mortality was determined at 48 h and 120 h after spraying; larvae were moved to artificial diet after 48 h. When tests involved XRD 473, surviving insects were placed on artificial diet and held until pupation, emergence, or death.