Euonymus scale, Unaspis euonymi (Comstock) (Homoptera: Diaspididae), is a serious pest of ornamental plants throughout the world. This armored scale commonly infests species of Euonymus, a genus of broad-leaved, woody plants used extensively in landscapes. Infestations of euonymus scale are characterized by unsightly, waxy scale coverings that encrust the stems and leaves of host plants. Feeding damage is visually manifested as chlorotic halos, circular discolorations on the leaf surface. Heavy scale infestations can reduce photosynthesis, stunt plants, abscise leaves, and kill plants.
Euonymus scale is attacked by a variety of natural enemies, which rarely regulate scale populations. Structural simplicity and scant biological diversity in ornamental landscapes may contribute to outbreaks of euonymus scale because large numbers of natural enemies are absent from simplified habitats. This situation could be rectified by planting flowers rich in nectar and/or pollen to attract and conserve natural enemies in ornamental landscapes. However, little is known about how populations of euonymus scale natural enemies are affected by flowers. Furthermore, the ability of flowers to provide an acceptable level of control has yet to be determined.
In 1999, we established E. fortunei plots (1 m2) surrounded by four flowering plant species (one per plot border) in three levels of floral density: no flowers (mulch only), low flower density and high flower density. Initial results reveal an increase in parasitism rate of euonymus scale by the parasitoid, Encarsia citrina Craw (Hymenoptera: Aphelinidae), as well as an increase in density of this wasp in flowering versus mulch plots. However, flower density does not appear to affect these parameters. Results suggest that planting flowers with E. fortunei may increase the potential for biological control of euonymus scale in ornamental landscapes.
Species 1: Homoptera Diaspididae Unaspis euonymi (euonymus scale)
Species 2: Hymenoptera Aphelinidae Encarsia citrina
Keywords: conservation biological control, floral resources
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA