Effects of low rates of pesticides on the control of pests and diseases of apples

Abstract

Fungicides and insecticides used at the recommended rate, and reduced recommended rates were applied at low volume (100 L ha-1) to apple trees in field experiments in South Australia from 1985 to 1988. At harvest the incidence of fruit damaged by fungi and insects was assessed on Golden Delicious, Red Delicious, Jonathan and Granny Smith cultivars. Mixtures of penconazole and mancozeb applied at the recommended rates of 800 mL and 4.5 kg ha-1 respectively as well as 25% and 10% of the recommended rates controlled apple scab completely in 1986, but were less effective in 1987. Azinphos-methyl applied at the recommended rate of 2.7 kg and 25% of the recommended rate reduced codling moth infestation to commercially acceptable levels of <2 % on Red Delicious only in 1987. Considerable cost savings are possible by using low rates of pesticides. Our results suggest that the use of low rates is more applicable to low valued cultivars such as Jonathans and orchards with low levels of pest and disease.