Fecundity of Boll Weevils unaltered following survival of LD50 dose of Malathion.

Authors: Armstrong, John; Greenberg, Shoil; SETAMOU, MAMOUDOU - TAES, WESLACO, TX.

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/2/2007
Publication Date: 7/5/2007
Citation: Armstrong, J.S., Greenberg, S.M., Setamou, M. 2007. Fecundity of Boll Weevils unaltered following survival of LD50 dose of Malathion. National Cotton Council Beltwide Cotton Conference, January 9-12, 2007, New Orleans, Louisiana. p. 356-360.

Interpretive Summary: The sublethal effects of malathion on female boll weevil reproduction has never been studied. Our study determined what a lethal dose was that would kill 50% of a female population and used it to determine what happened to the reproduction of boll weevils that survived that treatment by counting the number of eggs they oviposited, the number of eggs that actually emerged into larvae, and the total numbers of eggs inside the weevils that were fed artificial diet or cotton squares. Female boll weevils that survived a non-lethal exposure to malathion, and fed 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. Our findings that female boll weevils remain reproductive, if they survive nonlethal doses of malathion and are fed cotton squares, contributes 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 an LD50 value for a topical application of malathion 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.