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Oak Pests - A Guide to Major Insects, Diseases, Air Pollution and Chemical Injury


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LECANIUM SCALES
Eulecanium spp.

Importance. -- The lecanium scales are distributed throughout the United States. High scale populations severely reduce vitality, weaken the tree, and cause branch or crown dieback. They have been of greatest concern to shade and ornamental red and white oaks.

Identifying the Insect (figure 39). -- The body of the adult female is circular to ovoid, strongly convex or tortoise-shaped, and about .2 to .3 inch (4 to 7 mm) in diameter. Young females may be tan or mottled with black, but older females are reddish or dark brown. After their eggs hatch, the female body shells remain loosely attached to the bark. Scales commonly overlap and encircle portions of infested twigs.

Identifying the Injury. -- Trees of poor vigor or with branch and crown dieback should be examined closely for scale insects. Lecanium scales are most prominent on twigs during the spring and early summer.

Biology. -- Eggs are produced underneath the female in late spring. Eggs hatch in early summer and the immature insects seek feeding sites on the underside of leaves. In late summer, they migrate to twigs where they overwinter. They complete their development in the spring. There is usually one generation per year.

Control. -- Parasites and predators are effective in controlling infestations. However, insecticides are often used and are most effective against immature scales.

 

Figure 39

Figure 39. -- (a) Lecanium scale insects on a branch.
 
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