Location: Chemistry Research Unit
Title: Density-related Volatile emissions and responses in the red flour beetle, Tribolium castaneum Authors
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2011
Publication Date: April 8, 2011
Citation: Duehl, A.J., Arbogast, R.T., Teal, P.E. 2011. Density-related Volatile emissions and responses in the red flour beetle, Tribolium castaneum. Journal of Chemical Ecology. 37:525-532. Interpretive Summary: Red flour beetles are a major pest of stored products and the pest of greatest concern in flour mills. With the phasing out of methyl bromide fumigation, better sampling is needed to target integrated pest management control strategies. To seek out better chemical attractants based on the insect’s biology, experiments were conducted to determine if chemicals other than the previously identified aggregation pheromone 4,8-dimethyldecanal were emitted by the beetle as attractants. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, ARS, USDA in Gainesville, FL, examined the chemicals emitted by beetles in cultures at different densities and the responses of beetles to these chemicals to determine what the most attractive blends of chemicals emitted from other beetles were. Volatiles collected from groups of red flour beetles at different densities showed a clear relationship between density and rate of volatile emission; they also revealed an inverse correlation between emission of aggregation pheromone and emission of benzoquinones. The beetles detect benzoquinones and are be repelled by them, suggesting that increasing concentrations of these compounds may trigger dispersal. These relationships increase the knowledge base on red flour beetle chemical communication but indicate that other chemicals released by the beetle do not synergize attraction to the aggregation pheromone.
Technical Abstract: Intraspecific attraction depends both on the response of the attracted individual and on the cues provided by the attracting individual. These attracting cues are related not only to current conditions but are also a reflection of individual and population life history. By placing Tribolium castaneum (Herbst.) adults in flasks at increasing densities and monitoring the changes in volatile chemical emission over time these relationships were examined. Only certain chemicals were quantified: methyl benzoquinone, ethyl benzoquinone and 4,8-dimethyldecanal, all of which are known to impact the biology of T. castaneum. The flasks were used as sources for both quantification of the chemicals and for bioassays. Additional bioassays conducted with synthetic 4,8-dimethyldecanal, a known aggregation chemical, evaluated attraction with respect to population density. T. castaneum density affected both the release of volatile chemicals and the responses of conspecifics to those chemicals. The results indicated that while there were important effects of beetle density on chemical emission and response, none of the chemicals evaluated emerged as promising synergists to the current aggregation pheromone 4,8-dimethyldecanal. The benzoquinones released in response to stress and density acted as anti-aggregation pheromones along with their accepted function as a defensive secretion.