Population dynamics of pink bollworm on cotton was studied through male moths captured in the traps baited with sex pheromone ‘gossyplure’ and by its damage to the flowers and green bolls during 1978 and 1979 crop seasons. The number of pink bollworm male moths captured in traps were low up to August. Maximum moth population was recorded from the second fortnight of September to the second week of November. The population started declining after the first fortnight of November, indicating that most of the larvae had entered diapause due to the short photoperiod and low temperature. Incidence of pink bollworm on flowers was high up to the last week of August, after which it declined. While on green bolls its infestation started in the beginning of August and continued to increase up to the end of the season. A linear and highly positive correlation was found between the male moth catches in traps and the larval damage in flowers and bolls (r = 0.84 and 0.95 in 1978 and 1979 crop seasons, respectively).

Diapause in the pink bollworm, Pectinophora gossypiella, is a quantitative genetic character that is in turn regulated by external environmental factors. A naturally occurring non-diapause strain of the insect from south India and two diapause strains from Arizona (U.S.A.) were used in crosses to study the inheritance of diapause. The F progeny expressed a diapause response intermediate between the two parents and no clear dominance was evident for the non-diapause character. It was not possible to classify the phenotypes of backcross and F2 progeny in accordance with simple Mendelian ratios. Comparisons of reciprocal crosses indicated that the progeny from male parents of the Indian strain usually had a lesser incidence of diapause. Such sex related differences were more evident in F2 progeny and backcrosses. It is therefore concluded that diapause in the pink bollworm is inherited in a complex way and that non-diapause is not completely dominant over the diapause trait. The study also indicated that incomplete dominance for non-diapause involves a sex-linked gene.