There’s a new bug in town: Novel insect threatens white pine

By on June 29, 2016

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Numerous reports of eastern white pine in poor health have emerged from several counties in western N.C. Image: B. Heath, NCFS.

Numerous reports of eastern white pine in poor health have emerged from several counties in western N.C. Image: B. Heath, NCFS.

First impressions are lasting, and a newly-known insect is making a memorable one. Since mid-May, reports of eastern white pine in poor health emerged from several counties in western North Carolina. Trees in Ashe, Madison, Transylvania, Haywood, Mitchell and Swain counties had branch dieback, crown thinning, cankers (diseased areas of dead tissue), excessive resin outflow, and some have died. The underlying cause is a tiny scale insect, Matsucoccus macrocicatrices, which was first discovered in North Carolina in 2013.

The Matsucoccus scale was first recognized in the Southeastern U.S. in 2006 in Virginia on trees with lower branch dieback, cankers and some mortality. In 2012, a researcher noticed declining eastern white pine trees near a hemlock study site in northern Georgia and the Matsucoccus scale was subsequently identified. This tiny insect was previously only known to exist in Massachusetts, New Hampshire and parts of Canada. Follow-up surveys found the insect in other southern states, including North Carolina in 2013, where it was discovered in Jackson, Macon, Madison and Transylvania counties. Scientists are unsure whether this is an insect that has simply gone overlooked for years because of its tiny size and cryptic nature or if this is the newly-expanded range of an insect formerly known only from northeastern North America.

The tiny Matsucoccus scale is responsible for decline in health in eastern white pine in western N.C. Image: M. Cram, USFS.

The tiny Matsucoccus scale is responsible for decline in health in eastern white pine in western N.C. Image: M. Cram, USFS.

The Matsucoccus scale is typically found under lichen, in branch crotches, and embedded in cankers of eastern white pine trees. While it has been associated with several fungal species, the one most commonly found with the scale is Caliciopsis pinea which causes cankers from which large amounts of resin outflow. Caliciposis pinea and the disease it causes has been known to occur in North Carolina since the 1930s. It most often affects dense stands, suppressed trees and trees on sites with poor soils.

The reported impact in North Carolina is scattered and appear to affect trees on the forest edge more frequently.  Reports from other states indicate understory trees and lower branches may also be at-risk.

 

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