Are green leaf volatiles important for parasitoid wasp attraction in the field?

Abstract: Green leaf volatiles (GLVs) are commonly emitted by plants under herbivore attack. A broad range of laboratory studies have shown that GLVs can be used by predators and parasitoids of these herbivores to find their prey or hosts. The aim of this study was to evaluate the function of GLVs in the attraction of parasitoid wasps to maize plants under field conditions. In an experimental field, we planted maize lox10 mutants impaired in GLV biosynthesis alongside wildtype plants and lox8 mutants, which are, similar to lox10 mutants, impaired in the jasmonic acid pathway, but produce normal levels of GLVs. The plants were infested with herbivorous Spodoptera frugiperda larvae, an important pest of maize that abundantly occurs in the area. A week later, plants were harvested and larvae were recollected to determine the degree of parasitism. Overall parasitism levels were low, but contrary to expectations, tended to be highest on non-emitting lox10 plants, implying that GLVs were not of key importance for parasitoid attraction in the field.