Volatile organic compounds released by wheat as a result of striped shieldbug feeding and insect behaviour

The most popular plant protection method is chemical; however, this is often connected with repeated treatments. Therefore, eco-friendly strategies need to be investigated. A good alternative is to use the natural repellent properties of plants. The aims of this study were to determine how adult striped shieldbugs (Aelia acuminata L.) feeding on spring wheat plants affect the emission of volatile organic compounds (VOCs) and to determine the reaction of these insects to synthetic blends of VOCs. Using GC/MS for VOC analysis, we find that Aelia acuminata L. (1 or 2 adult pairs) significantly induced VOC emissions from wheat plants. In comparison with controls, larger amounts of (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, β-pinene, β-myrcene, (Z)-3-hexen-1-yl acetate, 1-hexyl acetate, 4-heptanone, (Z)-ocimene, linalool, linalool oxide, benzyl acetate, methyl salicylate, indole, β-caryophyllene and (E)-β-farnesene were released as a result of the biotic stress, with two pairs of insects causing a significantly stronger plant reaction. On the basis of the VOCs identified and their emitted concentrations for two pairs of feeding adult striped shieldbugs, two blends of VOCs were prepared in three concentrations: blend I—(Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, (Z)-3-hexen-1-yl acetate and 1-hexyl acetate, and blend II—(Z)-ocimene, linalool, benzyl acetate, methyl salicylate, β-caryophyllene and (E)-β-farnesene. Using an olfactometer (Y-tube) to study insect behaviour, it was found that the male striped shieldbugs were not attracted to any of the blends at any concentration. Female shieldbugs were attracted to blend I at concentration 1. As for the remaining concentrations of both blends, females and males were repelled, with the higher the concentration the stronger the insect reaction.