DDT for the protection of stored potatoes

Abstract

At the strengths used, DDT, derris and pyrethrum-piperonyl butoxide as dusts and DDT-impregnated Chapman sacks and sugar-bags were all efficacious in protecting stored tubers when the initial infestation was less than 4 P.er cent. DDT dusts, ranging in concentration from 0.5 to 2 per cent., and containers treated in DDT emulsions ranging in concentration from 0.5 to 2.5 per cent. arrested infestations varying from 8 to 35 per cent. satisfactorily. The higher levels of DDT were more efficacious, however, when the initial infestation exceeded 20 per cent. Results with pieces of DDT-impregnated burlap and DDT-treated paper strips placed among the tubers were not conclusive. A 2 per cent. DDT dust applied at the rate of 1 lb. per bag, and a dipping strength of 2 per cent. DDT emulsion for impregnating containers, were considered the most efficacious for general application in the field. Second-hand lightweight hessian sugar-bags provide a satisfactory alternative to the standard Chapman sacks for storing tubers. Multiple-layered paper bags are not suitable for storing tubers under Queensland conditions. Quantities of DDT are transferred to tubers when DDT-impregnated containers are handled. DDT residues on tubers, whether acquired from the container or from dust application, persist during storage but are reduced to within safe limits during handling from store and preparation for the table.