Could my Oak Tree have Kermes Scale?

Is your Oak tree looking sick, scraggly, droopy, or all of the above? It could be due to the insect Kermes scale.

What’s that?

Kermes scale is an insect pest of red and white oak trees, as well as the pin and Gambrel oaks. Northern Red Oaks often become infested with the Kermes scale, in particular, and are projected to be subject to heavy infestation here in Colorado during 2016.
The tan to brown female “scales” are 1/4” in diameter, round, immobile, and are covered with a protective convex shell that is an integral part of their bodies. Adult female scales are often found at the base of leaf stems and are fiendishly difficult to spot because they look very similar to the tree buds. Their eggs hatch in September and October, and crawlers then move to over-wintering sites on the tree’s branches and trunks.

Kermes scale is aggressive and can cause significant damage in oaks, and treatment is necessary when infestations advance to cover most of the tree – of course, the earlier treatment is implemented, the better prognosis for the tree.

How do I know if I have it?

The symptoms of Kermes scale infestation include:

leaves changing color,
sap oozing, and
twig dieback.
Heavy infestations cause “flagging”, in which the leaves on branch tips turn off-color, droop and often drop off.
Infested trees have reduced growth and vigor.
And as an additional pain point, yellowjackets may be attracted to and feed on the adult female scales.

examining an oak infected by Kermes scale in Boulder's Central Park

Kermes scale insects on oak twig

Kermes scale insect on oak twig.

Kermes scale insects on oak twig

Ugh! My tree looks like it does have this! What should I do?

ArborScape recommends a two-step approach for treating this infestation – a topical spray application, followed by systemic injection. Over-wintered scales can be treated with dormant horticultural oils in Spring, to smother any surviving scales, and crawler sprays should be applied in early Fall when eggs hatch and crawlers are seen on twigs.

Don’t want to try to diagnose and treat it yourself? ArborScape can provide a free assessment and treatment plan within 3 business days!
Call 303-806-TREE or click here to set up your evaluation now >>

ArborScape Staff

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