Lachancea thermotolerans, a Yeast Symbiont of Yellowjackets, Enhances Attraction of Three Yellowjacket Species (Hymenoptera: Vespidae) to Fruit Powder.

Previously, we showed that the symbiotic yeast Lachancea thermotolerans (Filippov) (Saccharomycetales: Saccharomycetaceae) is attractive to its Vespula (Hymenoptera: Vespidae) yellowjacket hosts when grown on media supplemented with grape juice. We hypothesized that "Concerto", a commercial strain of this yeast, could be combined with fruit powder to form a shelf-stable bait for trapping yellowjackets. Using molecular techniques, we first confirmed that Concerto yeast is indeed the species L. thermotolerans. We then tested whether: 1) Concerto yeast produces volatiles similar to those produced by L. thermotolerans isolated from yellowjackets, 2) Concerto yeast enhances attraction of yellowjackets to fruit powder, 3) a Concerto yeast/fruit powder bait interacts synergistically with a yellowjacket semiochemical lure, and 4) a synthetic analog blend of Concerto-produced volatiles attracts yellowjackets. Using gas chromatography-mass spectrometry, we demonstrated that the chemical composition of Concerto-produced volatiles closely resembles that produced by a yellowjacket-isolated strain of L. thermotolerans. In field experiments, addition of Concerto to fruit powder doubled its attractiveness to yellowjackets. Addition of the Concerto/fruit powder bait to a heptyl butyrate-based wasp lure revealed a weak additive effect. A three-component synthetic analog blend of volatiles identified from the Concerto/fruit powder bait attracted Vespula pensylvanica (Saussure), but no other yellowjacket species. Our results suggest that commercial L. thermotolerans in combination with fruit powder could be used as a yellowjacket bait, and that addition of yeast-produced volatiles to a commercial wasp lure may improve its attractiveness to V. pensylvanica. Further research should determine why the synthetic volatile blend failed to attract Vespula species other than V. pensylvanica.