Pesticide formulation concentrates should maintain their physicochemical stability from the time of preparation until field application. Literature information on pesticide stability is lacking at present, especially after field storage under the conditions of the operational spray programs for forest pest control. The present study provides information on the influence of water hardness, pH, formulation ingredients, carrier media, storage periods, and temperature fluctuations, on phase separation, pesticide hydrolysis, degradation and metabolism, in some simple formulation concentrates prepared in the laboratory, and in some complex formulation concentrates obtained from pesticide companies.
The investigation indicated that the greater the hardness of water, the greater the stability of the active ingredients. Formulants increased the storage stability of pesticides. Polymeric formulants of larger molecular mass provided greater stability to pesticides than the surfactants of smaller molecular size. The longer the storage period, the lesser the stability of pesticides. Highly water-soluble pesticides degraded to a much greater extent than the sparingly soluble ones. Degradation occurred much more in aqueous media than in non-aqueous media, and the type of metabolites formed differed in the two media. Commercial formulation concentrates made up of several ingredients provided metabolites different from those found in the simple formulations prepared in the laboratory. Pesticide degradation occurred to a much greater extent after storage of the commercial formulation concentrates under outdoor conditions at extreme fluctuating temperatures, than after storage in the laboratory at a constant temperature.