Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/18/2006
Publication Date: 11/28/2006
Citation: Cosse, A.A., Bartelt, R.J., Zilkowski, B.W., Bean, D.W., Andress, E.R. 2006. Behaviorally active green leaf volatiles for monitoring the leaf beetle Diorhabda elongata, a biocontrol agent of saltcedar. Journal of Chemical Ecology. 32:2695-2708. Interpretive Summary: The leaf beetle Diorhabda elongata has been successfully introduced into the U.S. from China as a biocontrol agent for saltcedar. Saltcedars were originally imported from Eurasia as ornamentals and for erosion control of streambanks and river channels. However, these fast-growing shrubs or small trees are invasive and have become a major component of Western riparian ecosystems causing serious environmental and economic damages. We have identified several volatile compounds that are emitted by the saltcedar plant, especially when the beetles are feeding on the foliage. A blend of four of these compounds was highly attractive to adult beetles in the field. Combining the host odor blend with the earlier reported pheromone of this beetle resulted in even stronger attraction. As such, the combined blend is a useful attractant in detecting the presence of D. elongata in newly colonized areas. This would be a very useful tool in the saltcedar biocontrol program.
Technical Abstract: Biological activity and chemistry of host plant volatiles were investigated for Diorhabda elongata, Brullé (Coleoptera: Chrysomelidae), a biological control agent for the invasive weedy tree, saltcedar (Tamarix spp., Tamaricaceae). Gas chromatographic-electroantennographic detection (GC-EAD) analysis of volatiles collected from adult D. elongata feeding on saltcedar foliage or from saltcedar foliage alone showed fifteen antennally active compounds. These compounds were more abundant in collections from beetle-infested foliage. Antennally active compounds were identified by GC-mass spectrometry (MS) and confirmed with authentic standards. The emissions of the most abundant GC-EAD active compounds, green leaf volatiles (GLV), were quantitated by GC-MS. A blend of four GLV compounds mimicking the natural blend ratio was highly attractive to male and female D. elongata in the field, and a combination of GLV and male-produced aggregation pheromone attracted greater numbers of D. elongata than did either bait alone. A preliminary experiment with a blend of seven additional GC-EAD active saltcedar volatiles did not show any behavioral activity. The combination of the pheromone and the green leaf odor blend could be a useful attractant in detecting the presence of biocontrol agent, D. elongata, in newly colonized saltcedar areas.