DIET-MEDIATED TERMINATION OF BOLL WEEVIL DORMANCY

Authors: Spurgeon, Dale; Suh, Charles

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2003
Publication Date: 5/15/2003
Citation: SPURGEON, D.W., SUH, C.P. DIET-MEDIATED TERMINATION OF BOLL WEEVIL DORMANCY. NATIONAL COTTON COUNCIL BELTWIDE COTTON CONFERENCE. 2003. pp. 1511-1514. (CD-ROM)

Interpretive Summary: The boll weevil is one of the most destructive insect pests that attack cotton. A key to the boll weevil's ability to infest and damage U.S. cotton has been its ability to survive the winter in a state of dormancy. This dormancy has been described as a diapause, which implies that the dormancy is triggered by environmental conditions preceding the onset of unfavorable conditions rather than by the unfavorable conditions themselves. Most studies of boll weevil diapause have focused on the factors promoting the dormancy, and little effort has been devoted to understanding how the dormancy is terminated. In this study, when weevils were exposed to cotton flower buds (squares) after feeding on cotton fruit (bolls) for 14 d, males did not terminate the diapause while the numbers of females in diapause declined. When weevils were starved for 1, 3, or 5 weeks between feeding on bolls and exposure to squares, more males terminated the diapause as the starvation period was increased. Female weevils terminated diapause at rates that were similar among the different starvation periods. Females that did not terminate the diapause also did not feed frequently. These results show that termination of the diapause is controlled somewhat differently in male and female weevils. Because of the possible relationship between feeding and diapause termination, the influence of activities that consume large amounts of energy, such as flight, should also be examined in relation to diapause termination.

Technical Abstract: Most studies of diapause in the boll weevil (Anthonomus grandis Boheman) have focused on factors influencing its induction. A more complete understanding of this survival mechanism also requires knowledge of the factors controlling diapause termination. Termination responses of diapausing weevils exposed to a known reproductive diet (cotton squares) were evaluated. In separate experiments, the reproductive diet was provided either immediately after a 14-d diapause induction period, or after 1, 3, or 5 weeks of starvation following diapause induction. Male weevils did not terminate diapause when exposed to the reproductive diet immediately after the diapause induction period, while the proportion of diapause in females decreased from 0.92 to 0.67 after the diet switch. When weevils were starved between diapause induction and exposure to the reproductive diet, males terminated diapause more frequently as the duration of starvation increased, while females terminated diapause at comparable rates after all durations of starvation. Females remaining in diapause despite exposure to the reproductive diet more often declined to feed than females terminating the diapause. Feeding responses of males were less consistent and more difficult to interpret. Our results indicate marked differences in the termination responses of the respective weevil sexes, and suggest the potential roles of energetically expensive activities such as flight should be examined for their influence on the propensity of weevils to feed and terminate diapause.