Insecticides for the control of the lucerne flea, Sminthurus viridis (L.), and the red-legged earth mite, Halotydeus destructor (Tuck), and their effects of population numbers

Abstract

Experiments are described which demonstrate effective insecticidal treatments for the control of the lucerne flea, Sminthurus viridis (L.), and the red-legged earth mite, Halotydeus destructor (Tuck.). As dual purpose insecticides, malathion/DDT, malathioli/lindane, and endrin all gave excellent results. The lower cost and lower mammalian toxicity of malathion/ DDT favour this mixture, which is now recommended for field use. Also effective against the lucerne flea were dieldrin, chlorthion, and "Diazinon". Lindane and "Dilan" gave good controlof the red-legged earth mite, but DDT was superior to both. None of the materials used for the control of the lucerne flea had an effective residual action, so that careful attention to the time of application of the insecticides was essential for optimum results. Treatment within 3-5 weeks of the rains which initiate hatching of the oversummering eggs is recommended. Eradication was not achieved by any of the treatments. The subsequent effect of insecticidal treatment on the population density of both pests is discussed. The numerical changes which followed the application of insecticides suggest that density-governing factors play an important part in the regulation of the numbers of both species.