Bionomics of the cotton flowerweevil Amorphoidea lata motschulsky (Coleoptera: curculionidae)

The study confirmed that all Amorphoidea populations in the Philippines belong to only one species but they showed considerable geographical variation from Luzon to Mindanao. The life cycle of the cotton flowerweevil, A. lata Motschulsky, was completed in 10.06 to 16.83 days. Eggs were laid singly at the base of the petals/ovary sheath and hatched in 1.40 to 3.54 days. The larval stage ranged from 5.66 to 7.86 days with two distinct periods (feeding and resting/pre-pupal period). The pre-pupal and pupal stages, lasted from 2.28 to 3.25 and 3.0 to 5.43 days, respectively. Adults emerged during the day, with the peak of emergence at 10:00 A.M. to 11:00 A.M. Newly emerged adults did not mate but fed within 5 to 64 minutes and were active flyers. A. lata was observed in the different cotton growing areas of the country. During the 1989-90 cotton season, its distribution and abundance were reported in ten cotton growing provinces being present throughout the flowering period of cotton. Adult flowerweevil preferred to feed on the petals rather than on the stigma and anthers. Both adults and larvae inflicted injuries on cotton flowers/young bolls. Injuries caused by adults were through feeding and egg deposition on the flower, while larval feeding on the ovaries/young bolls resulted in premature shedding of young bolls. Friedman's ranked test showed no significant ovipositional preference among the varieties tested, indicating that female weevils laid their eggs on any cotton variety. Based on flower/boll infestation records, percent damage was relatively high in Ilocos Norte, Cagayan and Pangasinan. The peak of infestation was recorded from January to March and the lowest was in December. The peaks of larval and adult populations were also registered from January to March. Seasonal fluctuations in flowerweevil population and infestation were influenced by the main and interaction effects of relative humidity, temperature, and solar radiation at a given number of days after emergence during October, November and December, 1989 plantings, respectively