Synthetic Herbivore-induced Plant Volatiles Increase Field Captures of Parasitic Wasps

Field evidence for attraction of parasitic wasps from the families Encyrtidae and Mymaridae to grapevines baited with synthetic versions of three herbivore-induced plant volatiles (HIPV) is presented. In a replicated experiment conducted in a juice grape vineyard, sticky cards in blocks baited with controlled-release dispensers of methyl salicylate (MeSA), methyl jasmonate (MeJA) or (Z)-3-hexenyl acetate (HA), trapped significantly greater numbers of Metaphycus sp. (Encyrtidae) than cards in unbaited blocks during May–September. Significantly greater numbers of Anagrus spp. (Mymaridae) were trapped in MeSA and MeJA-baited blocks than in unbaited blocks, during August–September. Greater numbers were recorded in HA-baited blocks in September only. Previous studies showed Encyrtidae and Anagrus spp. were not attracted to sticky cards baited with vials of MeSA, MeJA or HA. Possible reasons for attraction in this study are discussed including the possibility that synthetic, gaseous HIPV from controlled-release dispensers may stimulate plants to produce natural blends of parasitoid-attracting volatiles.