Survival and Control of the Boll Weevil, Anthonomus grandis, Around Overwintering Habitat in the United States
Feb 22, 2019
A field and a laboratory experiment were performed to evaluate factors that influence the overwinter survival of boll weevil, Anthonomus grandis Boheman, populations. Spring surveys of boll weevil densities were conducted as indicators of overwintering survival in 1994, 1995, 1996 and 1997 in four Arkansas counties. Approximately 1000 traps were placed adjacent to defined overwintering habitats near cotton fields. Traps near forested habitats consistently contained the highest average boll weevil catches among habitat types, while grassy field borders generally had the lowest mean trap captures. Trap captures near tree-line and brushy field border habitats were moderate. Larger and more significant differences between habitat types occurred during springs following colder winters. In the laboratory experiment, diapause-conditioned boll weevils were subjected to freezing temperatures within containers submerged in a cold circulation bath and held for one to eight hours. Results showed that temperature, duration of exposure, moisture and substrate were significant factors in boll weevil mortality. Mortality increased with temperature reduction and exposure time. The presence of dry substrate significantly improved weevil survival over those in empty containers at -10.0 and -12.5oC and over those in moist substrate at -5.0 to -12.5oC. Over 70% of weevils were able to survive temperatures of -2.5oC for eight hours, in either moist or dry substrate, while high (>75%) mortality occurred at -10oC or colder temperatures in moist substrate, even for short (1 hour) exposures. These results indicate that temperature and litter type within overwintering habitat microsites are important indicators of boll weevil survival.