Pesticide encapsulation using a starch-borate complex as wall material

A new technique has been developed for encapsulating pesticides for controlled release. The method consists in mixing starch, pesticide, and water; adding alkali to gelatinize the starch; and treating the mixture with boric acid. The solid product is a starch–borate adduct, entrapping the pesticide within small cells. Initially, the adduct is a rubbery gel which, when treated with alcohol or ground with additional pearl starch, yields particles suitable for drying to the 10–35‐mesh range. When the starch is used to break up the gel, the technique is useful for retaining water‐soluble compounds. Water‐insoluble pesticides, emulsifiable concentrates, and wettable powders are encapsulated and recovered in high yields. Acid‐labile pesticides such as diazinon are stable in the borate gel. The process was scaled up successfully by use of a double planetary mixer.