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Joseph F. Boggs, Ohio State University Extension, Hamilton County/Southwest District; Curtis E. Young, David J. Shetlar, James A. Chatfield, Erik A. Draper, Pamela J. Bennett, Gary Y. Gao, |
Other Sucking Insects
A number of species of soft scales seemed particularly abundant during the 2001 season. These included cottony maple leaf scale (Pulvinaria acericola), calico scale (Eulecanium cerasorum), Fletcher scale (Parthenolecanium fletcheri), and magnolia scale (Neolecanium cornuparvum).
Cottony maple leaf scale ovisacs were observed on the underside of sassafras leaves in southwestern Ohio in June. The ovisacs are conspicuous, elongated, white, cottony egg masses that may contain more than 2,500 eggs. By early September, crawlers had emerged from these ovisacs and settled along the leaf veins on the underside of the leaves. These observations illustrated both the wide host range of this insect and the vulnerability of this scale to late season control measures. Despite its common name, this scale will infest a wide range of host plants including dogwood, hollies, andromeda, honeysuckle, and sourgum.
Calico scale (Eulecanium cerasorum) continues to become more common in Ohio (7, 8). As with last season, this insect was found on dogwood, magnolia, and sweetgum in southwestern Ohio and on honeylocust and sweetgum in the northeastern part of the state. Additional hosts of this soft scale include maple, magnolia, tuliptree, and ornamental fruit trees. The scale normally does not kill trees, but it is capable of producing large quantities of honeydew that may be colonized by sooty molds, giving the host an unsightly appearance.
This globular blackish-brown soft scale is about 1/4 inch in diameter, and it is easy to recognize because of the distinct rows of squarish, white patches on the back. Its life cycle is similar to European fruit lecanium scale. Calico scale has one generation per year and overwinters on twigs as partially grown nymphs. As the spring progresses, the nymphs feed, molt, and mature into globular adults. In late spring to early summer, eggs are laid, and the hatching nymphs migrate to the undersides of leaves. In late summer to early fall, the nymphs molt to second instars and move from the leaves to stems, branches, and the trunk where they overwinter. Effective control strategies include insecticide applications made in July or August, targeting the first instar nymphs on leaves, or dormant oil applications made in early spring to kill overwintering second instar nymphs.