Magnolia Scale Fact Sheet

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Magnolia scale, Neolecanium cornuparvum (Thro), is one of the largest scale insects in Pennsylvania. It is native to the United States and is commonly found throughout the eastern part of the country. The magnolia scale removes fluids from the plant using its syringe-like mouthparts and may result in branch dieback or death of the plant if left unchecked.

Plants Attacked

Black sooty mold on magnolia leaves as a result of honeydew excreted by magnolia scale

The magnolias most commonly attacked are Star Magnolia (Magnolia stellata),
Saucer Magnolia (Magnolia soulangeana), Cucumbertree Magnolia (Magnolia acuminata) and Lily Magnolia (Magnolia liliiflora). It has also been reported that magnolia scale feeds on Daphne spp., Virginia Creeper (Parthenocissus quinquefolia), and Tuliptree (Liriodendron tulipifera).

Insect Identification

The over-wintering nymphs are dark gray-black and cluster together in large numbers on 1-2 year old branches of the host plant. In the early summer, the female magnolia scale develops a white waxy coating, which later disappears in August before newborn crawlers emerge. The mature female magnolia scale is 1/2" in diameter, smooth, elliptical, convex and dark brown to pinkish-orange in color. The male scale is much smaller (about 1/8"), and turns a translucent white color in early summer before developing into a tiny, pink to yellow gnat-like insect. Newly hatched crawlers are a medium brown color, getting darker after feeding commences.

Life History

Winter	Tiny, dark-colored nymphs over-winter on one-year or two-year old twigs.
Spring	The scale begins to feed and enlarge in size.
Summer-Fall	The male and female nymphs mature in late July-early August. The males emerge, mate with the females and die. In late August or early September, the females give birth to crawlers who wander for a short period before settling on a young twig, where they over-winter. There is one generation per year in Pennsylvania.

 

Damage Symptoms

A heavy infestation of female Magnolia scale on the twigs of magnolia	In mid-July, the white waxy covering on the female scales wears away as they near maturity

Magnolia scales are usually massed on the undersides of 1 and 2 year old twigs, with heavy infestations completely encrusting branches. Other indicators of a scale infestation include reduced foliage and flower production, undersized leaves and twigs, and a black sooty mold on the foliage. After digesting the plant fluid, the scale excretes a clear sticky liquid called honeydew, which provides an ideal substrate for the black sooty mold fungus to develop. Magnolia scale infestations often go unnoticed until the leaves and twigs of the host plant turn black with sooty mold. The honeydew also provides a food source, attracting ants, bees, wasps and flies.

Management Options

Biological	The larvae and adults of certain lady beetles feed on magnolia scale in late summer. Contact insecticides can kill beneficial insects and should not be used when they are present. In many cases magnolia scale come with the plant, so it is important to avoid purchasing infested plants.
Mechanical	Controls will be more effective if heavily infested branches are removed.
Chemical	In late fall and early spring the application of dormant horticultural oil will reduce the nymph population. In late August to early September, the application of insecticidal soaps or horticultural oil will help to manage the crawler stage. Controlling the crawlers is usually the easiest and most effective way of dealing with infestations. Contact insecticides do not readily control scale when their protective waxy covering is present. Control measures for magnolia scale.

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Authored by:
Katherine Mazzey, Penn State Extension Program Assistant
Michael Masiuk, Extension Agent, Penn State University - Allegheny County

Sources:
Hoover, G.A. (2000).Woody Ornamental Insect, Mite, and Disease Management. Penn
State College of Agricultural Sciences. pp. 38. http://woodypestguide.cas.psu.edu

Hoover, G.A. (2001).Juniper Scale. Entomological Notes, Department of Entomology,
Penn State University. http://www.ento.psu.edu/extension/factsheets/magscale.htm

Johnson, W.T. & Lyon, H.H. (1976). Insects That Feed On Trees And Shrubs, pp.354.
Comstock Publishing Associates. Cornell University Press.

Klass C. (1988). Magnolia Scale. Cornell University. Department of Entomology.
http://www.cce.cornell.edu/factsheets/pest-fact-sheets/old/wo.pst.magnolia.html

Shetlar, D. J. (2000). Magnolia Scale And Its Control. Ohio State University
Extension Fact Sheet. http://ohioline.osu.edu/hyg-fact/2000/2003.html

Townsend, L. (1996). Magnolia Scale. University of Kentucky Entomology.
http://www.uky.edu/Agriculture/Entomology/entfacts/trees/ef431.html