Hydrated Lime as an Insect Repellent

Some vegetable growers and the popular press commonly offer testimony as to the effectiveness of hydrated lime as an insect repellent. At the Fifth Annual Virginia Sustainable Agriculture conference, several noted producers and writers told how hydrated lime applied to the foliage of vegetable crops repelled a wide variety of insects including aphids, flea beetles, Colorado potato beetles, squash bugs and cucumber beetles. Numerical evidence to support this claim seems to be lacking in the scientific literature.

In 1992, experiments were conducted on eggplant, summer squash and bell peppers to determine the effectiveness of foliar-applied, hydrated lime as a plant protectant and an alternative to pesticides. Three treatments were tested on each crop: an untreated control, a standard chemical insecticide (Asana) and hydrated lime (50 pounds/acre). Five to eight weekly applications of the insecticide and lime were made, depending on the crop and insect problems present. Insects were counted and fruit was harvested on a weekly basis.

Hydrated lime was effective at repelling flea beetles on eggplant. However, the attribute was overshadowed by increased plant defoliation by Colorado potato beetle feeding, which reduced yields (61%) in the hydrated lime treatment compared with plants protected with the chemical insecticide. Yield was also reduced 25 percent for summer squash where hydrated lime was applied versus the insecticide treatment. This yield reduction was attributed to higher infestation levels and increased plant damage by the squash vine borer. The lime also failed to significantly reduce populations of aphids on eggplants and summer squash; cucumber beetles and squash bugs on summer squash; or European corn borers in peppers, compared to the untreated controls. The chemical treatment reduced populations of aphids, cucumber beetles and European corn borers.

Based on one year's results, hydrated lime did not appear to be a practical substitute for commercial pesticides on these commodities. Details of this study can be found in Volume 18 (1993) of the Entomology Society of America's Insecticide and Acaracide Tests.

Written by: Jude Boucher and Roger Adams, University of Connecticut Integrated Pest Management
Reprinted from the Grower, February 1993

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