Use of HIPV lures to evaluate natural enemy abundance, diversity, and phenology 

When deployed as baits within standard delta traps, herbivore-induced plant volatiles (HIPVs) facilitate efficient monitoring of adult parasitic Hymenoptera, green lacewings, predaceous Hemiptera, and hover flies in orchard systems. Squalene, geraniol, 2-phenylethanol, methyl salicylate, acetophenone, and phenylacetaldehyde were screened as promising new attractants of these and other natural enemies in Washington orchards. Differing trap types were also assayed for their potential to enhance/exclude certain taxa. Tens of thousands of specimens were caught during the 2009 growing season, representing a total of 78 morphospecies, across eight insect orders. Numerically, trap-catch was dominated by lacewings and parasitic Hymenoptera. While only five species of green lacewings were caught, at least 52 morphospecies of parasitic Hymenoptera were recorded. Trends in natural enemy phenology were assessed in relation to pest phenology. Although HIPVs are generally thought to involve just three trophic levels (plant, herbivore, and natural enemy), our data also show that parasitoids of natural enemies are responding to HIPVs, which indicates that four or more trophic levels are likely involved. HIPV-based trapping represents a powerful new method of assessing natural enemy abundance, diversity, and phenology in tree fruits and should help us better understand their population dynamics.