|Armstrong, John - Scott|
Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2006
Publication Date: 12/1/2006
Citation: Greenberg, S.M., Armstrong, J.S., Setamou, M., Sappington, T.W., Coleman, R.J., Liu, T. 2006. Circadian rhythms of feeding, oviposition, and emergence of the boll weevil (Coleoptera: Curculionidae). Journal of Insect Science. 13(6):461-467. Interpretive Summary: The boll weevil is a primary insect pest of cotton in non-eradicated areas of the USA, Mexico, and South America, and control of it is critical to cotton production. Better knowledge of the boll weevil's biology, ecology, and behavior is required to develop environmentally-safe and efficient strategies for controlling them. In this study, we estimate circadian rhythms of boll weevil emergence, feeding, and oviposition depending on different photoperiod, because daily cycle of light and darkness is the main environmental cue organisms use to synchronize circadian rhythms to the 24 h day. These findings will be vital to an understanding of the boll weevil ecology and evaluation of its reproductive strategies. Circadian rhythms of emergence, feeding, and oviposition of the boll weevils were still unknown prior to this study.
Technical Abstract: Circadian rhythm of feeding, oviposition, and emergence of boll weevil adults were determined at 5 different photophases (24, 14, 12, 10 and 0 hours) and a constant 27 deg C temperature, 65% RH in the laboratory. Squares from petri dishes, where they were exposed to boll weevil females, were removed and examined for feeding and oviposition punctures every 4 hours in the day (0700-1900 h) and every 12 h in the night (1900-0700 h) during eight consecutive days. Cohorts of randomly selected egg-punctured squares were sampled from ovipositing females at 0700, 1100, 1500, and 1900 during 24 hours and under different photophase treatments, and maintained in petri dishes at 271 +/- 1 deg C, 65% RH. Dishes were observed twice daily (1900 and 0700 h) for adults emerging in the day or night. Circadian rhythm of oviposition was not effected by the length of the photophase. The boll weevil has round the clock circadian rhythm of oviposition, with a daytime preference. We observed that 82.4-86.0% of the boll weevil eggs were deposited between 0700-1900, and 14.0-17.6% between 1900-0700 h during a 24 h period. Feeding of boll weevil females significantly increased from 1900 to 0700 at photoperiods 24:0, 14:10, and 0:24 L:D, h, but feeding was not significantly different at photoperiods 12:12 and 10:14 L:D, h. The circadian rhythm of emergence depended significantly on the time of oviposition and the length of the photophase. Investigation of boll weevil circadian rhythm provides a better understanding of boll weevil ecology and reveal better weak links that will control and improve on targeting their reproductive strategies.