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Baseline data on susceptibility levels to azinphosmethyl and permethrin were generated on five field-collected populations of the pink bollworm, Pectinophora gossypiella (Saunders), from Arizona and Southern California, relative to a standard susceptible laboratory strain. The field strains showed less than 2-fold resistance to azinphosmethyl but exhibited variable levels (1.3- to 18.3-fold) of resistance to permethrin. Resistance of pink bollworms to permethrin seems to be correlated with the pattern of insecticide-use prevalent in the localities studied. Strains from Yuma, Phoenix and Westmoreland exhibited highest levels of resistance to permethrin. Synergism of permethrin with an oxidase inhibitor, piperonyl butoxide (PBO), and an esterase inhibitor, S,S,S-tributyl phosphorotrithioate (DEF), produced less than 2-fold synergism in the Yuma strain. Results suggest that nonmetabolic factor(s) may be involved in permethrin resistance of the Yuma field strain since neither PBO nor PBO/DEF combination suppressed resistance completely. It is possible that pink bollworm resistance is at least partially conferred by the khr-gene. Rearing of two field strains collected from Marana and Yuma under insecticide-free conditions resulted in reversion of resistance 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. Monitoring of resistance in field strains should be performed preferably in the F₁ generation. Subsequently, 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. Selection of larvae with both azinphosmethyl and permethrin resulted in higher levels of resistance in larvae than in adults. Results suggest that azinphosmethyl possesses a low degree of selectivity for development of resistance in pink bollworm adults. Fourteen to 16 generations of selection with azinphosmethyl and permethrin produced ca. 2- and 9-fold resistance, respectively, in the adult stage. A laboratory-selected strain showing ca. 13-fold resistance was used in reciprocal crosses with a susceptible laboratory strain. The F₁ results suggested that inheritance of permethrin resistance was autosomal and partially dominant. Chi-square analysis of responses of backcross progeny indicated that resistance seems to be conferred by a major gene under the influence of minor gene(s).

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The sampling dynamics of the pink bollworm (Pectinophora gossypiella (Saunders)) were studied during the cotton growing seasons of 1976, 1977, and 1978. Different sampling methods were employed each year to compare sampling intensity and to compare whole plant samples with susceptible boll samples. Analysis of variance data indicated that significant differences in mean boll infestation levels occurred between small areas of a field (ca. 1 acre), but that these differences were masked when larger units (ca. 10 acres) of a field were used as the sample area. From these data it was found that samples yielded the most accurate pink bollworm infestation estimate when taken from as large an area of the field as possible. Data indicated that accuracy improved only 2 to 3 percent when sample size increased from 60 bolls to 100 bolls. Bolls taken from whole plant samples were as accurate as susceptible boll samples if there was an equal number of bolls in each sample. Sample accuracy was nearly stable for fields 20 to 40 acres in size. A sequential sampling plan for pink bollworm was developed using the binomial distribution. Decision levels were established using the 6 and 12 percent boll infestation levels with α and β levels of 0.2. Approximately 50 percent of the sampling time can be saved over conventional 100 boll samples with very little loss of accuracy for a spray-no spray decision based upon an economic threshold value of 15 percent pink bollworm infestation.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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