BIOLOGY AND ECOLOGY OF COTTON PESTS EMPHASIZING MANAGEMENT OF BOLL WEEVILS
Title: Reproductive potential of field-collected overwintering boll weevils (Coleoptera: Curculionidae) fed on pollen in the laboratory
Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2008
Publication Date: June 15, 2009
Citation: Greenberg, S.M., Jones, G.D., Adamczyk Jr, J.J., Setamou, M., Liu, T., Armstrong, J.S., Coleman, R.J., Eischen, F.A. 2009. Reproductive potential of field-collected overwintering boll weevils (Coleoptera: Curculionidae) fed on pollen in the laboratory. Insect Science. 16(4):321-327.
Interpretive Summary: The boll weevil overwinters in the southern United States in the adult stage. Survival of overwintering boll weevils is a critical determinant in the severity of infestation in the subsequent cotton season and is a principal element in the present area-wide eradication programs. Alternative foraging resources play a significant role in adult boll weevil survival, especially during cotton free periods. Boll weevils are primarily a pollen feeding insect. Plant pollens may provide energy and nutrients that increase boll weevil survival during the absence of cultivated cotton. Boll weevil ingesting and digestion of pollen may be one of the principal evolved survival mechanisms in fall and winter of the Lower Rio Grande Valley of Texas when cotton is not available. But boll weevil females without access to cotton,
resorb their eggs and enter into reproductive diapause. The effects of pollen feeding on overwintering boll weevil females reproductive maturity and potential to transfer them to cotton fruit has not yet been thoroughly investigated. The reproductive potential of overwintering boll weevil females collected in different months is an important consideration in determining the success of any control strategy. Basic research designed to address the unanswered questions of reproductive potential overwintering boll weevil females will contribute to the existing boll weevil eradication, containment, and management programs, and will be vital for the successful expansion of such programs into subtropical and tropical regions.
The reproductive potential on cotton squares of overwintered boll weevil, Anthonomus grandis grandis (Boheman), females collected from pheromone traps in September, November, and January and after feeding them one, three, and five weeks on plant pollens was determined in the laboratory at 27ºC, 65% RH, and a photoperiod 13:11 (L:D) h. Timing of pollen feeding overwintering boll weevils did not significantly influence egg and feeding punctures, puncture ratios (egg to total punctures) during the months of parent weevil collections and when provided cotton squares on a daily basis. However, all these parameters are significantly different when we compared mean data between months of boll weevil collections regardless of the timing of pollen feeding. During the cotton-free period in the Lower Rio Grande Valley, boll weevil females are entering in reproductive diapauses. When weevils were provisioned daily with cotton squares, the preovipositional periods of female parents captured in September, November, and January were 5, 9, and 14 days, respectively. The rate of feeding by females was significantly less during winter (January) than fall (September), and this may have affected the rate of diet-mediated termination of dormancy. No differences in male reproductive parameters were observed during the cotton-free period compared with males captured during mid-season cotton growth (June), except for testes size. The number of oocytes in the ovarioles, and the number of oocytes containing yolk in boll weevil females were significantly lower during September, November, and January compared with June. Female parents collected in September produced a significantly higher percentage of eggs yielding adult progeny than did female parents collected in January. Life table calculations indicated that females collected in September increased an average 1.2-fold higher each generation (Ro) than females collected in November and 10.7-fold than those in January. The reproductive potential of overwintering boll weevil females collected in different months is an important consideration in determining the success of any control strategy.