Abstract:
Intraguild interactions are known to trigger competition among phytophagous
insects that depend on the same food source, which may have implications on
natural enemy performance. Here, we tested the hypothesis that intraguild
interactions between the greenhouse whitefly, Trialeurodes vaporariorum, and
the South American tomato pinworm, Phthorimaea absoluta on the host plant
tomato would affect performance of the pinworm ectoparasitoid Bracon
nigricans. In oviposition bioassays, P. absoluta females significantly laid more
eggs and were attracted to tomato plants infested with T. vaporariorum than
uninfested plants. Additionally, T. vaporariorum infestation decreased B.
nigricans parasitism on P. absoluta larvae and attraction to tomato plants. In
coupled gas chromatography-electroantennographic detection (GC-EAD)
recordings, antennae of P. absoluta and B. nigricans females detected 18 and
15 components, respectively from the herbivore-induced volatiles, which were
identified by GC-mass spectrometry (GC-MS) as green leaf volatiles (GLVs) and
terpenes. In dose-response behavioral assays, P. absoluta and B. nigricans
responses varied with the composition and concentration of blends and
individual compounds tested. Whereas P. absoluta was attracted to GLVs and
terpenes, B. nigricans avoided most of these chemicals, especially the GLV (E)-2-
hexenal and terpenes d-3-carene, and (E)-caryophyllene. The results suggest
that herbivore intraguild interactions can influence the behavioral ecology and
performance of natural enemies which may have evolutionary significance. Also,
these specific GLVs and terpenes can be exploited in the management
of P. absoluta.
