Adherent Starch Granules for Encapsulation of Insect Control Agents

Abstract

Granule carriers for insect control agents have been used for many years, especially for control of soil-borne pests. Granular baits have not been practical for foliar application because they do not stick well and are susceptible to removal by wind or rain. A simple and economic technique to prepare adherent granules has been developed. The granules are made of starch which, when applied to wet surfaces and allowed to dry, will adhere even in the presence of additional water. Granules were formulated by mixing pregelatinized starch with a water-organic solvent solution. Solvents tested included methanol, ethanol, n-butanol, 2-propanol, acetone, and l,4-dioxane. The resulting mass, after drying, easily crumbled into particles that could then be sieved to desired particle sizes. Assays that measured resistance to wash-off demonstrated that granules made with 2-propanol were retained on both glass and cotton leaf surfaces, whereas granules made with water alone washed off easily. Granules made with 2-propanol and Bacillus thuringiensis Berliner showed no loss of insecticidal activity when compared with granules made with water alone. A field study testing adult Diabrotica virgifera virgifera LeConte attraction to traps baited with p-methoxycinnamaldehyde encapsulated within starch granules demonstrated a sustained rate of release of the attractant over a 12-d period. Possible benefits of an adherent pesticidal bait formulation are discussed.