• Reversion of Permethrin Resistance in Field Strains and Selection for Azinphosmethyl and Permethrin Resistance in Pink Bollworm (Lepidoptera: Gelechiidae)

      Osman, Abdelgadir A.; Watson, Theo F.; Sivasupramaniam, Sakunlala; Silvertooth, Jeff; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991)
      Rearing of two field strains (Maratha, Yuma) of pink bollworm. Pectinophora gossypiella (Saunders). from Arizona under conditions free of insecticides resulted in reversion of resistance (in adults) in four and five generations. respectively. to levels close to that found in the susceptible laboratory strain. Permethrin resistance in these field strains is unstable and is apparently in its early phase of development. Results suggest that monitoring of pink bollworm resistance in field strains reared in the laboratory should be performed in the F₁ generation. Subsequent selection studies were performed on both larval and adult stages to investigate the capacity of the pink bollworm to develop resistance in both life stages. Fourteen generations of selection of larvae and adults with azinphosmethyl produced 1.9- and 1.6-fold tolerance. respectively. in the adult stage. Sixteen generations of larval selection with permethrin generated 9.7-fold resistance in adults. while 14 generations of adult selection produced 8.8-fold resistance in adults. Azinphosmethyl evidently possesses a low degree of selectivity for development of resistance in pink bollworm adults. Selection of larvae with both azinphosmethyl and permethrin seemed to generate higher levels of tolerance in larvae than in adults.
    • Susceptibility of Field Populations of Pink Bollworm (Lepidoptera: Gelechiidae) to Azinphosmethyl and Permethrin

      Osman, Abdelgadir A.; Watson, Theo F.; Sivasupramaniam, Sakunlala; Silvertooth, Jeff; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991)
      Responses of five field -collected populations of the pink bollworm. Pectinophora gossypiella (Saunders). from Arizona and southern California. were compared with those of a standard. susceptible -laboratory strain. Field strains showed less than twofold difference in response to azinphosmethyl at LD₅₀ but had variable levels (1.3- to 18.3-fold) of response to permethrin. Strains from Yuma and Phoenix (Arizona) and Westmoreland (California) had highest levels of resistance to permethrin.