Oviposition of diamondback moth Plutella xylostella females is affected by herbivore-induced plant volatiles that attract the larval parasitoid Cotesia vestalis

A mixture of four volatile compounds, (Z)-3-hexenyl acetate, alpha-pinene, sabinene and n-heptanal, emitted from cabbage plants infested by diamondback moth [DBM; Plutella xylostella (L.)] larvae attracts Cotesia vestalis (Haliday), a major parasitoid of DBM larvae. The volatiles may affect other organisms, such as DBM conspecifics, other herbivores and carnivores. Here, we studied whether the volatiles affect the oviposition behavior of DBM females. In a climate-controlled room, five pots of komatsuna plants (Brassica rapa var. perviridis L. cv. Rakuten; leaf vegetable) were placed in an acrylic box. For the treatment, we placed a bottle-type dispenser of the volatiles (0.01% in a triethyl citrate solution) next to the center pot. For the control experiment, we used a container with plants and triethyl citrate only. The presence of the volatiles did not affect the number of eggs per plant. Interestingly, DBM females laid more eggs on the adaxial leaf surfaces in the treatment compared with the control. This is the first study showing that plant volatiles affect the oviposition site preference of herbivores on leaves. The results are discussed in relation to the application of attractants for DBM control in commercial greenhouses.