The development of sex pheromone-mediated mating disruption to control Coleophora deauratella (Lepidoptera: Coleophoridae): a major pest of red clover, Trifolium pratense L., in Canada

The red clover casebearer, Coleophora deauratella Leinig and Zeller (Lepidoptera: Coleophoridae), is an invasive seed predator of red clover (Trifolium pratense L.) in North America. Larval infestations have resulted in ≥80% seed loss in Ontario and Alberta, Canada. Insecticide trials illustrate the cost of application is not offset by seed yield, and there are currently no registered insecticides against this pest. An effective, relatively species specific, alternative to insecticide is sex pheromone-mediated mating disruption. Initial small-plot (0.25 ha) experiments to assess the potential for communication disruption of C. deauratella found the number of male C. deauratella captured in pheromone-baited traps was reduced by ≥99% in pheromone treated plots compared to untreated controls. The success of these initial studies, allows us to elucidate the mechanisms which may act on C. deauratella to disrupt mating. Field studies using both the full attractive pheromone blend (100:10 ratio of (Z)-7-dodecenyl acetate to (Z)-5-dodecenyl acetate) and the unattractive major component ((Z)-7-dodecenyl acetate) alone both successfully reduced trap captures compared to untreated control plots, but the mechanisms appear to differ. Further, laboratory electroantennograms on males pre-exposed for 1 hour to either the full pheromone blend or major component alone determined that adaptation to both pheromone compounds occurs.  Competitive attraction appears to be the main mechanism of disruption when the full pheromone blend is used, whereas non-competitive mechanisms, adaptation/habituation or sensory system imbalance, occur when the unattractive major component alone is used.