Comparative Development, Reproduction, and Oviposition of Pink Bollworm (Lepidoptera: Gelechiidae) on a Resistant Okra-Leaf Cotton and Commercial Upland and Pima Cultivars

Selected life-history characteristics of pink bollworm, Pectinophora gossypiella (Saunders), were studied in three upland (‘Deltapine 90’,‘DES-119’, and ‘WC-12NL’), Gossypium hirsutum L., and one American Pima (‘Pima S-6’), G. barbadense L., cottons in three separate trials during 1990 and 1991. Larval developmental times (egg hatch to larval cutout from bolls) were shortest on ‘Pima S-6’ bolls in all three trials (overall mean 205 ± 4 degree-days [12 and 32.5°C lower and upper thresholds, respectively)), and longest on WC-12NL, a nectariless, okra-leaf cotton with known resistance to pink bollworm, in one of three trials (overall mean, 248 ± 5 degree-days). Prepupal (range of overall means, 56–58 degree-days) and pupal (145–150 degree-days) developmental times were not affected by cotton type. Larval survival averaged from 40 to 50%, and did not differ among cottons. Prepupal (range of overall means, 90–96%) and pupal survival (80–88%) was significantly higher on ‘WC-12NL’ bolls and lower on ‘Pima S-6’, respectively, in separate trials. Significantly fewer ‘Pima S-6’ bolls were infested with pink bollworm eggs early in the season and fewer ‘WC-12NL’ bolls were infested during the middle part of the season in 1990 and on the last sample date in 1991. The mean number of eggs per infested boll (range of overall, means, 5.3–9.4) did not vary over the season for a given cotton in either year, but significantly fewer eggs were laid on ‘WC-12NL’ bolls in both years compared with the other cottons. Fecundity of adults from larvae reared on the four cottons varied between trials and was significantly greater on ‘Pima S-6’ in one trial. Ambient temperatures, measured within the canopy in 1991, varied only slightly between the four cottons, with weekly heat-unit accumulations differing by <5 degree-days. Resistance of WC-12NL’appeared to be largely manifested through reduced oviposition on bolls. Accelerated larval development and slightly higher fecundity of moths on ‘Pima S-6’ suggest that this cotton, in comparison with several upland cultivars, may be more susceptible to pink bollworm in the field. The site-specific accuracy of predictive models for pink bollwornl phenology and population growth might be enhanced through parameter adjustments for different cottons.