Host plant volatiles as tools for monitoring and manipulating natural enemies

Field-scale deployment of host plant volatiles (HPVs) has shown much potential in recent augmentative and/or conservation bio-control studies. When loaded within slow-release lures, HPVs allow researchers to monitor or manipulate the spatial distributions of natural enemy populations. In Washington’s apple orchards, we screened HPV “cocktails” for their attractiveness to the resident insect taxa. Our findings revealed parasitoid biodiversity not previously known to exist within northwestern orchards, and also showed how remarkably abundant certain species were. In 2009, trap-catch was dominated by lacewings and parasitic Hymenoptera, though thousands of syrphids and predatory Hemiptera were also caught. Early work indicated that our most attractive lure blend consisted of geraniol, 2-phenylethanol, and methyl salicylate. To discern whether all components of this blend were attractive, we assayed the independent and interactive effects of this blend’s three components. Our findings indicated that sensitivity to certain combinations of these compounds was specific to each insect taxon, suggesting that HPV-based trapping strategies can be tailored to a taxon of interest. These data also provide useful assessments of the phenology of some of the most abundant natural enemies. In 2010, further screening of promising materials demonstrated that phenylacetaldehyde and acetophenone were highly attractive compounds to certain insect taxa, including pollinators. Identification of natural enemy complexes revealed that HPVs may be widely exploited by the natural enemies of natural enemies, which would have implications for bio-control strategies focusing on natural enemy herding.