The Effect of Field-Applied Insecticides on Beneficial Insects of Citrus in California

Abstract

The authors present observations made from 1907 to 1947 concerning the effect of field applied insecticides on beneficial insects. HCN tent fumigation, distillate and coal oil sprays and lime sulfur sprays as used in the period from 1907 through the succeeding 15 yrs. had little important influence on parasites and predators. The introduction of white oil sprays and combination treatment (oil spray followed by fumigation) in the twenties along with increased and more intensive treatment has been very destructive to many parasites and predators, some of which have almost completely disappeared. Recently, with the advent of DDT treatments in central California for thrips and scale control, summer applications (May through Aug.) have decimated the beneficial ladybird Rodolia cardinalis so that serious outbreaks of cottony cushion scale have developed. However, winter treatments of DDT, Sept. through March, have not caused serious outbreaks.