Submitted to: American Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2007
Publication Date: 12/18/2007
Citation: Showler, A.T. 2007. Subtropical boll weevil ecology. American Entomologist. 53:240-249.
Interpretive Summary: Although a great deal of research has been conducted on the boll weevil in temperate cotton, relatively little is known about its ecology in subtropical/tropical areas, which extend from South Texas to Argentina. Research on subtropical boll weevil food sources during the growing season and cotton-free overwinter season has shown that boll weevils in the subtropics can survive the winter without going into quiescent diapause, and that certain stages or sizes of cotton fruiting bodies enable boll weevil reproduction better than others. Subtropical ecology of the boll weevil is substantially different from temperate regions, and control measures can be developed which capitalize on knowledge of the pest’s subtropical ecology.
Technical Abstract: Although a great deal of research has been conducted on the boll weevil, Anthonomus grandis grandis Boheman, in temperate cotton, Gossypium hirsutum L., relatively little is known about its ecology in subtropical/tropical areas, which extend from South Texas to Argentina. Instead of diapausing during winter, boll weevils in the subtropics are active and reproductive year-round if host plants are available. Predators (excluding areas with imported fire ants) and cold winter temperatures are not key factors behind subtropical boll weevil population dynamics, but availability and quality of food are critical. During the growing season, boll weevil populations respond to the changing quality of cotton fruit, which influence boll weevil reproduction and longevity, and susceptibility of cotton fruit to injury. Weevils within fallen squares are often killed by desiccation, unless buried and insulated by in-season cultivation. Substantial numbers of boll weevils remain in the field after harvest, presumably in fallen cotton fruit. Although desiccation can kill them, weevils inside fruit on the soil surface during subtropical winters survive better than buried ones. Boll weevils can reproduce during subtropical winters on volunteer cotton and a few other plant species, but survival over winter is probably facilitated more by available food. Common subtropical foods that can sustain adult boll weevils over winter are orange, grapefruit, and prickly pear endocarps. Long-distance movement appears to be passive and opportunistic because boll weevils generally remain in the area, surviving in citrus orchards, and possibly other sources of food. Ecology-based spraying and cultural tactics are described.