The Insecticidal Efficiency of DDT Deposits Applied to Apple Foliage as Solutions or Emulsions

Abstract

The toxicity of deposits of DDT on leaves as a contact insecticide is affected by factors tending to reduce the deposits. Among these is penetration of DDT into the leaf-tissue where it is lost for this purpose. A study was made of the influence of formulation upon penetration as judged both by chemical recovery of DDT from the surface of treated apple leaves and by the toxicity of deposits on such leaves to the stored-products pest, Tribolium confusum Duv. Penetration was shown to increase from suspension through emulsion to solution and also, relatively, as the concentration of DDT in a given formulation was reduced. The rate of loss of these superficial deposits by weathering was found to fall off regularly with time of exposure. The DDT inside the leaf was not available as an insecticide for the insect used in these tests.