Plant volatile aldehydes as natural insecticides towards stored product beetles.

BACKGROUND: Infestation by stored-product pests causes serious losses in food and feed commodities. Among possible strategies against these pests, which aim to reduce the use of synthetic insecticides, including fumigants, natural insecticides produced by plants represent one of the most promising approaches for their ecochemical control. Three six-carbon and nine-carbon aldehydes, natural plant volatiles produced by the plant lipoxygenase pathway, were tested for their insecticidal activity against five species of stored-product beetles in feeding, fumigation and combined bioassays. RESULTS: The compounds (2E,6Z)-nonadienal, (2E)-nonenal and (2E)-hexenal were incorporated into feeding discs in feeding bioassays or evaporated from filter paper in closed glass chambers in fumigation tests. Beetle sensitivity to aldehydes differed according to the different treatments. The highest activity was obtained by (2E)-hexenal in fumigation tests, with the LC50 ranging from 4 to 26 mg L-1, while (2E, 6Z)-nonadienal was the most effective in feeding tests, giving LD50s ranging from 0.44 to 2.76 mg g-1 when applied to feeding discs. Fumigation tests in the presence of wheat grains confirmed that (2E)-hexenal was the most effective compound, with a calculated LC99 ranging from 33 to 166 mg L-1. CONCLUSION: The results of both feeding and fumigation tests indicated that natural plant aldehydes are potential candidates to control stored-product beetles.