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Mineral Film Foils Cotton Pests

By Ben Hardin
March 19, 2001

A nontoxic white mineral called kaolin may one day equal insecticides at preventing boll weevils and other pests from attacking cotton plants. In laboratory and small-scale field tests, Agricultural Research Service scientists found that the weevils tended to overlook plants coated each week with a spray mixture of the light-reflective kaolin and water. The weevils usually went elsewhere to feed and lay their eggs.

Cotton farmers normally spray entire fields five to seven times in boll-weevil-infested areas. Farmers begin spraying when pinhead-sized cotton buds, called squares, appear, and they continue spraying until bolls are formed and ready to bloom.

Entomologist Allan Showler at the Kika de la Garza Subtropical Agricultural Research Center, Weslaco, Texas, envisions spraying portions of fields with kaolin, possibly diverting the weevils to cotton trap crop areas sprayed with insecticides. The idea may become more practical when researchers find a way to curb rain from washing off kaolin, so it can be applied fewer times per season.

Showler found that most boll weevils avoided physical contact with cotton squares that had been sprayed with a commercial kaolin formulation. He concluded that the kaolin likely made the squares less visually appealing.

Kaolin is now federally registered for use in suppressing insect damage to a number of fruit and vegetable crops. Growers meeting organic standards have also accepted it.

ARS scientists Michael Glenn and Gary J. Puterka at Kearneysville, W.Va., conceived the idea of using inert films made from kaolin to ward off insects and disease. Research and development resulted in seven patent applications filed jointly by ARS and Engelhard Corporation of Iselin, N.J.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

Scientific contact: Allan Showler, ARS Kika de la Garza Subtropical Agricultural Research Center, Weslaco, Texas; phone (956) 969-4812, fax (956) 969-4800,