STARCH-ENCAPSULATED PESTICIDES FOR SLOW RELEASE

Advantages of controlled-release pesticide systems may include a less active agent and fewer applications, more effective control of the target organism, reduced toxicity to nontarget organisms, and reduced environmental pollution. Such systems are being developed and a few are being marketed based on containment of the pesticide within either a polymer matrix or coating. This paper reports results of a research program which was carried out in order to develop a simple procedure to encapsulate a broad range of biologically active materials within a starch matrix. Besides the simplicity of the procedure, the availability of starch and its low cost, the coating material will biodegrade and will leave no residue in the environment. The procedure consists of oxidatively crosslinking starch xanthate in an aqueous system in the process of the biologically active material. Incorporating a small amount of latex with the starch xanthate before crosslinking slows the rate of release of the pesticide. Also, the particulate product can be readily coated with an oxidatively coupled starch xanthate-latex layer to further reduce the rate of release of the active agent. Results of a test program (slow release) with starch-encapsulated pesticides are tabulated.