Effects of tobacco- and aphid-derived volatile compounds on the host-searching behavior and fecundity of <i>Aphidoletes aphidimyza</i> (Diptera: Cecidomyiidae): implications for pest control

The effects of volatile organic compounds (VOCs) from tobacco and Myzus persicae (Sulzer) (Homoptera, Aphididae) on the host-searching behavior and fecundity of Aphidoletes aphidimyza Rondani (Diptera, Cecidomyiidae), a key aphid predator, were investigated. The olfactory responses of A. aphidimyza adults to VOCs from healthy tobacco plants (HTPs), mechanically damaged tobacco plants (MDTPs), aphid-damaged tobacco plants without aphids (A-DTPs), aphid-carrying tobacco plants (A-CTPs), honeydew (H), and M. persicae (MPs) were assessed by electroantennography (EAG) and behavioral bioassays. A. aphidimyza exhibited significant differences in their preferences for different odor sources, as follows: A-CTPs > A-DTPs > MDTPs > HTPs > H > MPs. Their fecundity varied significantly following exposure to different VOCs from the tobacco-aphid system, being highest for A-CTPs and A-DTPs, which exceeded those of the other odor sources. Gas chromatography-mass spectrometry (GC-MS) identified 18 highly abundant VOCs from 6 odor sources. EAG revealed that the females detected these compounds in a concentration-dependent manner, exhibiting the strongest responses to n-hexanol, benzaldehyde, methyl salicylate, hexanoic acid, cis-3-hexenol, (E)-beta-farnesene, and (E)-6,10-dimethyl-5,9-undecadien-2-one, which elicited significant EAG responses at varying concentrations. Exposure to 50 μl/ml n-hexanol, cis-3-hexenol, (E)-beta-farnesene, 0.1 μl/ml methyl salicylate, hexanoic acid, or (E)-6,10-dimethyl-5,9-undecadien-2-one significantly increased the fecundity of A. aphidimyza. A 10:0.1:0.1:50:10:0.1 mixture of n-hexanol: methyl salicylate: hexanoic acid: cis-3-hexenol:(E)-beta-farnesene:(E)-6,10-dimethyl-5,9-undecadien-2-one (M3) significantly enhanced the behavioral responses and fecundity of A. aphidimyza, compared to those associated with individual VOCs or the blank control. These findings indicate that M3 elicited positive chemotactic responses in adult A. aphidimyza, and holds significant potential for precise aphid control using A. aphidimyza.