Effects of horticultural oil and foliar- or soil-applied systematic insecticides on euonymus scale in pachysandra

Abstract

The relative abilities of horticultural oil, acephate, and imidacloprid to control euonymus scale (Unaspis euonymi) throughout the canopy of Japanese pachysandra (Pachysandra terminalis) were compared. Distribution of scales and the level of parasitism were also determined. Horticultural oil gave the greatest level of control (99%) when applied in the dormant season followed by an application that targeted mobile stages of the insects during the summer. Summer applications of acephate gave good control (66%), while imidacloprid was not effective. Most of the live and parasitized scales were observed in the middle and basal portions of the plant canopy. Rates of parasitized scales never exceeded 25% in the control plots. Rates of parasitism were too low to distinguish differences among rates of parasitism in the 4 treatments.