Studies on New Pesticide Formulations

Pesticides are required to satisfy the following conditions at present: (1) a high safety standard, (2) high efficacy, (3) low prices. Screening probability of new pesticides has decreased and it has become extremely difficult to develop new ideal pesticides. In such a situation, improvement in formulations and application technologies weigh a lot in order to satisfy the above conditions. Labor-saving on spraying is also desired. As a means to meet such demands, various studies have been done on new pesticide formulations. Developments of new pesticide formulations and new application fields for existing pesticides would be comparable to inventions of new pesticides. Besides, the cost and time required for such developments would be less than those for the developments of new pesticides. From the viewpoint of economization the evaluation of new formulations for existing pesticides will be more favorable. With this understanding, we have been working to develop various kinds of new pesticide formulations. Fenitrothion microcapsule (MC) has been developed for control of cockroaches, termites and insects that attack plywoods. The main way of action of fenitrothion MC against cockroaches was trampling. When trampled by cockroaches, fenitrothion was released burstly to kill them just like a land mine destroys a tank. Also an eating mechanism was involved to some extent. The contact efficacy depended on the strength of the MC and the diameter/thickness (D/T) ratio. To termites, the main way of action was biting and sticking to appendages, followed by self- and mutual-grooming. When used for plywood panels, fenitrothion was stabilized in alkaline phenol resin to give longer residual efficacy. Pyrethroid MC was applied to agricultural uses, in which the biological efficacy depended on D/T, phytotoxicity and rain fastness on T, fish toxicity and acute toxicity on D×T. Fenvalerate and fenitrothion concentrated emulsions were developed by using suitable water-soluble polymers as dispersing agents. Main characteristics of the formulation was the decrease in toxicity and irritation, and the decrease in drift phenomena. Procymidon dry flowable was formulated by the spray drying method. This formulation was less phytotoxic, and physicochemical properties were favorable. Solid EC was formulated by using hydrolized starch. Flo-dust was shown to be usable as wettable powder as well. Calcined synthetic hydrated silicone dioxide improved the residual efficacy of fenitrothion wettable powder for residual spray application. When polyethyleneglycol or polypropyleneglycol was used in the EC formulation without any emulsifiers, acute toxicity and irritation reduced. Thermal decomposition mechanisms of organophosphorous insecticides and pyrethroids were clarified and stabilization methods were proposed. In the near future, research on pesticide delivery systems and the developments of various kinds of functional formulations will become important in order to meet recently growing demands for a higher safety standard, higher efficacy, lower prices, more labor-saving, better formulation properties and the development of new application fields.