Biology of magnolia scale

Magolia scale, Neolecanium cornuparvum (Thro), is one of the most conspicuous scale insects in North America. It feeds solely on trees in the genus Magnolia and is native to the eastern and southern portions of the United States. Although it feeds on native magnolias, magnolia scale does not ordinarily reach pest levels on native magnolias that are growing in an appropriate environment. It can, however, become a pest on non-native magnolias, and several factors, such as tree stress due to inappropriate growing conditions, may have predisposed these plants to attack by magnolia scale. Due to increased plantings of non-native magnolias that grow well in cooler climates, but pushing the bounds of cold tolerance for these trees, and because of the tendency to grow these plants in native clay soils and shade that is not appropriate for trees, magnolia scale has become a growing problem in Wisconsin over the past 10 years. Little is known about the biology of this insect, particularly in northern states, such as Wisconsin, where the climate is very different than in the scale’s native range. Magnolia scale biology was observed during regular intervals during 2006-2008. The size, color, consistency of the exoskeleton and associated components, molting events, presence of males, presence of eggs, and presence of parasitoids, as well as any other associations, were noted each week. This poster presents the results of these observations.