POPULATION DYNAMICS OF OVERWINTERING BOLL WEEVILS, ANTHONOMUS GRANDIS GRANDIS (BOHEMAN) IN THE LOWER RIO GRANDE VALLEY OF TEXAS

Authors: Greenberg, Shoil; Sappington, Thomas; Coleman, Randy

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2004
Publication Date: 6/14/2004
Citation: Greenberg, S.M., Sappington, T.W., Coleman, R.J. 2004. Population dynamics of overwintering boll weevils, Anthonomus grandis grandis (Boheman) in the Lower Rio Grande Valley of Texas. In: Proceedings of the Beltwide Cotton Conferences, January 5-9, 2004, San Antonio, Texas. 2004 CDROM.

Interpretive Summary: The boll weevil is a major insect pest of cotton for which the National Cotton Council estimates annual crop losses and control costs of $300 million in the U.S. Control of this insect is critical to cotton production, and an important control strategy is the reduction of overwintering weevil populations. Survival and reproductive condition of overwintering boll weevils were studied in the subtropical Lower Rio Grande Valley of Texas. Weevils were captured in traps throughout the year, but the number of captured weevils decreased significantly after the cotton harvest until spring planting. In addition, weevils became less fit for survival and reproduction during the overwintering period. These findings will aid in the identification of opportunities for improved effectiveness and economics of control of overwintered boll weevils, and the successful expansion of boll weevil eradication programs into subtropical and tropical environments.

Technical Abstract: Survival, and morphological, physiological, and reproductive changes in overwintering subtropical boll weevils, Anthonomus grandis grandis Boheman, were studied. The number of boll weevils captured per trap declined significantly from the postharvest period to the beginning of the spring over two overwintering seasons: 2000-2001 and 2001-2002. The proportion of males and females trapped did not differ significantly. Ninety percent of captured weevils died by 47.6 days when fed, while 90% of unfed weevils died after 9 days. This trend was not affected by month of capture. Female weevil fat body ratings were significantly greater at the beginning of fall than in the spring. Most male weevils from September through March were rated as lean (82.5-100%). No differences in male reproductive parameters were observed in those captured during the cotton free-period compared with the middle of growing cotton season (June), except for testes size which was larger in the latter. The percentage of females with oocytes in their ovarioles, and the percentage containing oocytes with yolk, were significantly lower in September than in June. During October-March, we did not observe any females with chorionated eggs, whereas in June 96% females contained them. We found that weevil females can oviposit eggs in the Lower Rio Grande Valley during overwintering period after feeding 7-20 days on a reproductive diet of cotton squares. Females captured later in the winter fed at a higher rate than those captured in the early fall.