Entomology Publications Entomology 12-2006 Circadian rhythms of feeding, oviposition, and emergence of the boll weevil (Coleoptera: Curculionidae) Shoil M. Greenberg United States Department of Agriculture J. S. Armstrong United States Department of Agriculture Mamoudou Setamou Texas A & M University - Weslaco Thomas W. Sappington United States Department of Agriculture, [email protected] Randy J. Coleman United States Department of Agriculture Follow this and additional works at: http://lib.dr.iastate.edu/ent_pubs See next page for additional authors Part of the Biology Commons, Entomology Commons, and the Physiology Commons The ompc lete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ ent_pubs/227. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Entomology at Iowa State University Digital Repository. It has been accepted for inclusion in Entomology Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Circadian rhythms of feeding, oviposition, and emergence of the boll weevil (Coleoptera: Curculionidae) Abstract Circadian rhythm of feeding, oviposition, and emergence of boll weevil adults were determined at five different photophases (24, 14, 12, 10, and 0 hours) and a constant 27°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 during daylight (0700–1900 h) and every 12 h at night (1900–0700 h) over 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 27 ± 1°C, 65% RH. Dishes were observed twice daily (1900 and 0700 h) for adults emerging at day or night. Circadian rhythm of oviposition was not affected 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 and 1900 h, and 14.0%-17.6% between 1900 and 0700 h during a 24-h period. Feeding of boll weevil females in photoperiods 24: 0 h (complete light) and 0: 24 h (complete darkness) did not significantly change between 0700–1900 h versus 1900–0700 h, while the daily cycle of light and darkness in other photoperiods significantly increased the feeding punctures from 0700–1900 compared with 1900–0700 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 reveals potential weak links for improving control technologies targeting their reproductive strategies. Keywords Anthonomus grandis, emergence, circadian rhythm, oviposition, photophase Disciplines Biology | Entomology | Physiology Comments This article is from Insect science 13 (2006): 461, doi:10.1111/j.1744-7917.2006.00116.x. Rights Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The onc tent of this document is not copyrighted. Authors Shoil M. Greenberg, J. S. Armstrong, Mamoudou Setamou, Thomas W. Sappington, Randy J. Coleman, and Tong-Xian Liu This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ent_pubs/227 Insect Science (2006) 13, 461-467 Circadian rhythms of boll weevil 461 Circadian rhythms of feeding, oviposition, and emergence of the boll weevil (Coleoptera: Curculionidae) SHOIL M. GREENBERG1 , J. SCOTT ARMSTRONG1 , MAMOUDOU SETAMOU' 2 , THOMAS W. SAPPINGTON3 , RANDY J. COLEMAN1 and TONG-XIAN LIU2 1USDA-ARS-SARC-BIRU, 2Texas A&M University Agricultural Experiment Station, Weslaco Texas and 3USDA-ARS- CICGRU, Ames, Iow, USA Abstract Circadian rhythm of feeding, oviposition, and emergence of boll weevil adults were determined at five different photophases (24, 14, 12, 10, and 0 hours) and a constant 27oC 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 during daylight (0700-1900 h) and every 12 h at night (1900-0700 h) over 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 27 ± 1oC, 65% RH. Dishes were observed twice daily (1900 and 0700 h) for adults emerging at day or night. Circadian rhythm of oviposition was not affected 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 and 1900 h, and 14.0%-17.6% between 1900 and 0700 h during a 24-h period. Feeding of boll weevil females in photoperiods 24: 0 h (complete light) and 0: 24 h (complete darkness) did not significantly change between 0700-1900 h versus 1900-0700 h, while the daily cycle of light and darkness in other photoperiods significantly increased the feeding punctures from 0700-1900 compared with 1900-0700 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 reveals potential weak links for improving control technologies targeting their reproductive strategies. Key words Anthonomus grandis, emergence, circadian rhythm, oviposition, photophase DOI 10.1111/j.1744-7917.2006.00116.x Introduction legless white grubs develop through three instars and a pupal stage within the fruit. The adult emerges inside the The boll weevil, Anthonomus grandis grandis (Boheman), fruit and chews its way out. The complete life-cycle re- is a key pest of cotton in non-eradication areas of the USA, quires 15-20 days. Both adult and immature weevils Mexico, and South America. Female weevils oviposit eggs damage cotton. Adults cause damage via feeding and in cotton squares (flower buds) and young bolls, where oviposition punctures on fruiting structures, while the grubs feed within the fruit. When bracts of damaged squares open, which is referred to as flaring, damaged Correspondence: Shoil M. Greenberg, USDA-ARS-SARC- squares are usually aborted by the plant and drop to the BIRU, 2413 East Highway 83, Weslaco, Texas, 78596, USA. Tel: ground. 956 9694806; fax: 956 969 4888; email: sgreenberg@weslaco. The activity rhythms of many insects are governed by ars.usda.gov abiotic factors, but light is the basic factor that sets the www.blackwellpublishing.com/ins 461 Insect Science 13, 461-467 462 S. M. Greenberg et al. timing of the activity phase in nearly every case (Harker, Experimental conditions 1961; Edwards, 1964; Tshernyshev, 1996). The daily cycle of light and darkness is the main environmental cue organ- Five different photoperiods were used [10:14; 12:12; 14: isms use to synchronize circadian rhythms to the 24-h day. 10; 24:0; and 0:24 (L:D) h] and all photophases were A circadian rhythm of activity is a major characteristic of initiated at 0700. Temperature in all cases was maintained insects affecting their ecology (Neville, 1967; Pittendrigh, at 27±1oC and relative humidity at about 65%. Homoge- 1972; Roberts, 1965, 1974; Beck, 1980; Tshernyshev, neous groups of 10 weevil females were entrained to each 1984), and it is important to correctly select the optimal of the five photoperiods for 5 days prior to studies. photoperiod for their maintenance. The time of peak activ- ity is determined by physiological processes that trigger Circadian rhythm of feeding and oviposition. behavioral reactions in insects. The objectives of this study were to determine the effects of photoperiod on circadian Females were individually placed in Petri dishes (150 rhythms of: (i) feeding; (ii) oviposition; and (iii) emer- mm×15 mm) with a 4-cm circular screened (nylon) win- gence of boll weevil adults. dow on the top. Five uninfested squares were exposed to boll weevil females at 0700, 1100, 1500, and 1900 h during the 24-h period. For feeding and oviposition, five groups of Materials and methods 10 females were held in environmental chambers pro- grammed for the five different photoperiods as described Boll weevil culture and cotton squares above. Squares were removed and examined for feeding and oviposition punctures every 4 hours from 0700 to 1900 All boll weevils for these experiments were reared and 12 hours from 1900 to 0700 for 8 consecutive days. under similar conditions in the laboratory from field- Unsealed punctures were considered as feeding punctures. collected infested squares. Approximately 1 000 infested Oviposition punctures were distinguished by a frass plug squares were collected from the ground in cotton fields in and/or a waxy substance either closing the puncture or the Lower Rio Grande Valley of Texas during May-June present on the periphery of the puncture. Everett and Ray 2003. Squares were carefully dissected, and those con- (1962) reported a correlation between the numbers of such taining live third instars were reclosed and held within sealed punctures and the numbers of eggs that the weevils screen cages in an environmental chamber at 27 ± 1oC, deposited. We used the numbers of sealed punctures as a 65% RH, and a photoperiod of 13:11 (L:D) h. Tempera- relative estimate of egg numbers. ture and humidity were monitored by a Fisher-brand Traceable Relative Humidity Meter with temperature Circadian rhythm of emergence readout (Fisher Cat.