Submitted to: Insect Science and Its Application
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2006
Publication Date: 6/1/2006
Citation: Armstrong, J.S., Setamou, M., Showler, A.T., Greenberg, S. 2006. Sublethal effects of malathion on boll weevil (Coleoptera: Curculionidae) fecundity when maintained on cotton squares and artificial diet. Insect Science and Its Application. 13:287-292. Interpretive Summary: The non-lethal effects of malathion insecticide on female boll weevil reproduction has never been studied. Our study determined the dose required to kill 50% of a female population and used it to determine the impacts on reproduction of boll weevils that survived that treatment. Female boll weevils that survived a non-lethal dose of malathion and fed on optimal size cotton squares laid as many eggs as did the untreated weevils, but the diet (cotton fruit or artificial diet) used to maintain the weevils influenced the results of the assays. Our findings that female boll weevils remain reproductive, if they are exposed to non-lethal doses of malathion and feed on cotton fruit, contribute toward a greater understanding of the impact of malathion on boll weevil reproduction in the field and will be important in the ongoing effort to eradicate the boll weevil from the United States.
Technical Abstract: We determined a LD50 value for malathion applied topically to 3-d-old female boll weevils and used it to treat groups of mated females reared from field-infested cotton squares. Survivorship, oviposition, egg development, and body fat condition were compared to nontreated control weevils fed cotton squares or artificial diet. A significant separation in the survivorship of malathion treated females versus controls occurred over 96 h of observations regardless of whether the weevils were fed squares or artificial diet. However, female survivors maintained on artificial diet oviposited significantly less than those reared on cotton squares, regardless of being treated with malathion or acetone. Mean numbers of nonchorionated eggs, chorionated eggs, and the total numbers of eggs were greater in square-fed weevils than in weevils fed artificial diet. Eighty-nine percent of surviving females were lean and reproductive when fed cotton squares in both treatments, while 25% of those fed artificial diet were lean and reproductive. Female boll weevils that survive a non-lethal exposure to malathion, and feed on optimal size cotton squares, oviposit as much as the controls, but the diet used to maintain the weevils can influence the results of the assays.