Obscure Scale Control

Obscure scale is mainly found on oaks. They can also attack maple, hickory, walnut, and willow trees. Obscure scales attach to branches and feed on plant sap. Obscure scale can cause dieback of branches and limbs and may affect whole trees. These scale insects blend in so well with the bark that it is easy to mistake them for flakes of bark. Obscure scales are often a pest on stressed urban trees.

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(The following information is edited from http://lpm.uga.edu/ornamentals/obscurescale.html See this website for photos of the scale.)

Identifying Obscure Scale

Fully enlarged adult female obscure scale covers may reach 1/8 inch in diameter. They are circular, brown to gray, slightly convex, with central shed skins that are black when rubbed. Male covers are smaller and broadly oval. This scale insect develops in overlapping clumps. There is one generation a year.  

Look on three to four-year-old branches for overlapping gray scale covers. Scrape off covers to determine if scales are alive since covers of dead scales may remain attached. In midsummer, live adult female scales are light purple.

Watch in July for Obscure Scale Crawlers!

Immature scales overwinter and scale ‘crawlers’ appear in July. Crawlers are the young, mobile form of scale insects. Scout in mid-July to determine amount of crawler activity. Look under covers in the dormant season for the small, yellow immature crawlers to see if oil sprays are needed.

Obscure Scale Control

Crawlers are much easier to control with insecticides than adult scales. Spray summer oil in late July to kill newly settled crawlers. In the winter, concentrate dormant oil sprays on three- to four-year-old growth to reduce over-wintering scale populations.

Several parasites of obscure scale are active when the scale crawlers appear in July. Look for holes in scale covers to estimate the level of parasitism. Avoid synthetic insecticide sprays at this time to keep from killing these helpful scale parasites.

An orange fungus (Nectria) can grow on the scale (see photo). The fungus can also kill scales like obscure scale.

Read and follow all label directions when using any pesticide!

For more information:

Call your local <?xml:namespace prefix = st1 />Extension Agent at (800) ASK-UGA1 or locate your local Extension Office at http://www.caes.uga.edu/extension/statewide.cfm

Obscure Scale from University of Kentucky - http://www.ca.uky.edu/entomology/entfacts/ef432.asp

Pest Management Handbook (Follow all label recommendations when using any pesticide) - www.ent.uga.edu/pmh/