Effect of wheat plant volatiles on aphids and associated predator behavior: selection of efficient infochemicals for field study

Semiochemicals are involved in tritrophic interactions and affect the behaviors of both herbivores and beneficial insects. Many volatile molecules from the wheat plant [Triticum aestivum L. (Gramineae)] have previously been identified. To understand their effects on aphids and related auxiliaries. [Methods] The impact of four of these volatiles ; methyl-salycilate, cis-3-hexenyl acetate, hexenol, and 1-hexanol, was tested on the wheat aphid [Sitobion avenae (Fabricus)(Homoptera:Aphididae)] and two major predators of this pest encountered in field crops, the hoverfly (Episyrphus balteatus (DeGeer) (Diptera: Syrphidae)] and the multicoloured Asian ladybird [Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)].Different doses of these chemicals were tested by performing four arm-olfactometer and wind-tunnel assays. [Results] The results show that methyl-salycilate seemed to be attractive only toward H. axyridis but 3-hexenyl acetate and hexenol were attractive to both S. avenae and H. axyridis. However, these positive responses decreased with increased dose of the tested compounds. 3-hexenyl acetate also induced positive response in E. balteatus but 1-hexanol was more attractive to aphids than to their natural enemies. [Conclusion] In conclusion, these results highlight the potential benefit of combining methyl-salycilate,3-hexenyl acetate and hexenol in push and pull traps aimed to control S. avenae. Contrary to the three aforementioned compounds, 1-hexanol did not seem to have much potential as a semiochemical for the biological control of aphids. Key words wheat, volatiles, infochemicals, aphid, predator, behaviour