Certain essential plant oils, widely used as fragrances and #avors in the perfume and food industries, have long been reputed to repel
insects. Recent investigations in several countries con"rm that some plant essential oils not only repel insects, but have contact and
fumigant insecticidal actions against speci"c pests, and fungicidal actions against some important plant pathogens. As part of an e!ort
aimed at the development of reduced-risk pesticides based on plant essential oils, toxic and sublethal e!ects of some essential oil
terpenes and phenols have been investigated using the tobacco cutworm (Spodoptera litura) and the green peach aphid (Myzus persicae)
as model pest species. In this paper I review (i) the range of biological activities of essential oils and their constituents; (ii) their toxicity
and proposed mode-of-action in insects; (iii) their potential health and environmental impacts as crop protectants; and (iv)
commercialization of pesticides based on plant essential oils