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Diapause Response of the Boll Weevil (Coleoptera: Curculionidae) to Feeding Period Duration and Cotton Square Size

Dale Spurgeon, Charles Suh, Jesus Esquivel
Journal of insect science 2018 v.18 no.5 pp. 1-9
Anthonomus grandis grandis, Gossypium, adults, cotton, diapause, eclosion, ecology, females, longevity, males, overwintering, pesticide application, pests, temperature, Mexico, Texas
Distribution of the boll weevil, Anthonomus grandis grandis Boheman, in the U.S. has been greatly reduced by eradication efforts. Still, it remains a key pest of cotton (Gossypium spp.) in the New World, and has proven difficult to eliminate from Mexico and southern Texas. In those regions, improved knowledge of boll weevil overwintering ecology may benefit efforts by eradication and management programs. Adult diapause in the weevil is well documented, but the influences of the length of the feeding period between weevil eclosion and assessment of diapause remain unstudied. We examined diapause incidences and associated survival patterns of weevils fed for 7, 14, or 21 d after adult eclosion. Diapause status of females, based on dissection, was less influenced by feeding duration compared with males. For males, highest diapause incidence occurred after 14 d of feeding compared with 7 or 21 d. Feeding duration influenced host-free survival of both sexes and highest survival was observed after 14 d of feeding, although many weevils were long-lived (more than 80 d) after each feeding period duration. Also, males exhibited higher survival compared with females, and survival of both sexes was higher after feeding on large squares compared with smaller squares. However, the factor most influencing survival was temperature, with lower temperatures producing longer-lived weevils than higher temperatures. These results suggest an optimal feeding period for induction of diapause and maximized host-free longevity. These findings may permit improved timing of late-season insecticide treatments aimed at reducing overwintering populations, and thereby improve effectiveness of eradication and management programs.