Buckwheat Flower Volatiles Attract Peristenus spretus and Enhance Its Field-Level Parasitism of Apolygus lucorum

Volatile compounds play indispensable roles in the interactions among host plants, herbivores and natural enemies. Previous studies showed that the addition of buckwheat strips in cotton fields could attract Peristenus spretus, the dominant parasitoid of Apolygus lucorum, and enhance its parasitic activity. Through the combined analysis of Y-tube olfactometer, solid-phase microextraction (SPME), gas chromatography-mass spectrometer (GC-MS) and electroantennography (EAG), we found that male and female P. spretus responded to compounds present in buckwheat flowers. The five major components of buckwheat flowers, cis-3-hexenyl acetate (Z3HA), 4-methylanisole, 4-oxoisophorone, p-methylphenol and 2-ethylhexyl salicylate, all had a significant attraction to P. spretus adults and led to positive electroantennogram responses, especially for 10 mg/mL 4-oxoisophorone, indicating the components played a key role in the selection behavior of P. spretus to buckwheat flowers. Additionally, field trials showed that the five volatiles could significantly increase the parasitism by P. spretus. Our study screened the key active components of buckwheat flower volatiles that have an attractive effect on P. spretus, revealing its behavioral selection mechanism and emphasizing the important role of plant volatiles on host selection and parasitism of parasitic wasps, providing a theoretical basis for the development of attractants for P. spretus and the reduction of pesticides in the field to promote conservation biological control (CBC) of A. lucorum.