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Pest Information

Oak kermes

  • Latin Name: Kermes spp.
  • Common Name: Oak kermes
  • Other Names: N/A

Pest Details

Origin:

These are native insects in North America.

Biology:

There are as many as 32 species of oak kermes scales in North America, and they occur throughout the continent where oaks are present. While natural enemies do tend to contain these scales they can cause dieback and defoliation when present in heavy numbers. They also create a great deal of sooty mold that drips onto surfaces below. Each female lays up to 3,200 eggs in early spring, and these hatch within a month. This first generation matures by mid-summer and a second generation may occur in warmer climates. First and second instars overwinter in crevices on the bark of the host tree.

Identification:

The mature females create a wax cover that may be from 5 to 8 mm across. It is light brown to whitish and very bulbous in shape, with 4 or 5 distinct lines or indentations running across the scale, giving it almost a “brain” like appearance. The mature females are found at the terminal tips of twigs as well as at the base of leaves.

Characteristicts Important to Control:

Dormant or summer oils may be effective in killing the scales, as well as contact insecticides applied when the first instar crawlers are present, which may be from early to late summer. Applications need to concentrate on terminal twigs and foliage. Determining the effectiveness of the control effort is difficult. The wax scales adhere tightly to the plant, even when the actual insect is no longer living, and very close examination beneath the scale may determine whether the insect itself is dead or alive.

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