Pure and Applied Chemistry

Abstract: Plants respond to insect attack by releasing complex blends of phytogenic volatile organic compounds. Selection of a host plant by the leafminer Liriomyza huidobrensis is influenced by such volatile chemicals (allelochemicals) released by the host plant. In the case of potato plants, the allelochemicals identified are mainly volatile monoterpenes and sesquiterpenes. A potato plant that is already infested by other individuals of the same species of insects shows a quantitative difference in emission of such allelochemicals, which in turn plays an important role in the host preference behavior exhibited by the insect. Olfactometer tests (using whole, potted potato plants as well as excised leaves) showed that L. huidobrensis adults were more attracted to already infested plants for feeding and egg-laying than they were to uninfested plants, demonstrating that volatile chemicals from infested plants function as kairomones in this insect-plant relationship. However, when the potato plants were grown in soil treated with aqueous neem extract, this relationship was disturbed and the insects did not exhibit any consistent feeding or egg-laying response to neem-treated infested or uninfested host plants. This indicates that neem compounds disturb secondary metabolite production in the potato plant, which in turn has an influence on insects that use volatile plant allelochemicals as cues for host identification and location. Results of this study can help in a better understanding of neem as an environment-friendly botanical pesticide for use in sustainable agriculture.