Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2006
Publication Date: August 1, 2006
Citation: Showler, A.T. 2006. Short-range dispersal and overwintering habitats of boll weevils (Coleoptera: Curculionidae) during and after harvest in the subtropics. Journal of Economic Entomology. 99(4):1152-1160.
Interpretive Summary: Adult boll weevils are known to overwinter in subtropical habitats, but the timing of dispersal from harvested cotton fields and the extent to which one overwintering habitat is preferred over others have not been evaluated. This study found that boll weevils do not emigrate from harvested cotton fields in a single pulse, but instead they tend to gradually concentrate in and around treelines during the fall, then concentrations fall in the treelines by spring and increase in citrus orchards and specific "hot spots." The increased understanding of when boll weevils disperse and concentrate in specific habitats will assist in monitoring overwinter populations as well as offer potential targets for off-season control tactics.
Field experiments in the subtropical Lower Rio Grande Valley of Texas determined the extent of adult boll weevil dispersal from cotton fields during harvest operations and the non-cotton-growing ('overwinter') period between 1 September and 1 February. Using unbaited large capacity boll weevil traps placed at intervals extending outward from commercial field edges, boll weevils were not moved in substantial numbers during harvest much beyond 30m, primarily in the direction of prevailing winds. Traps placed in fallow cotton, citrus, lake edge, pasture, treeline, sorghum, and sugarcane habitats during the overwinter period collected the most boll weevils in the fallow cotton fields and adjacent treelines during the fall. However, the greatest abundances of boll weevils were found in citrus orchards in the spring, before newly-planted cotton fields begin to square. One of the three lake edges also harbored substantial populations in the spring. Egg development in females was not detected November-April, but in cotton fields most females were gravid May-August when cotton fruiting bodies were available. Mated females as determined by discoloration of the spermatheca, comprised 80-100% of the female population during November and December declined to 50% in February, indicating a reduction in physical activity, until percentages increased in March and April.