Beech Scale Discovered in Allegan County

Article by Shawn Kelly, Conservation District Forester for Allegan, Barry, and Ottawa Counties.

Allegan County is now the 25th county within the Lower Peninsula to play host to the exotic pest known as Beech Scale, which in conjunction with an exotic fungus has caused the mortality of millions of American beech trees in Michigan to date.

Until recently Kent County represented the southern most county suffering from this detrimental pest complex. Together, beech scale and the exotic fungus Neonectria faginata infest stands of beech leading to the fatal beech bark disease.  Wind dispersed beech scale colonize beech trees taking refuge on rough patches of bark and on branch scars protecting them from being washed away by rain and wind.  As scale populations build on the tree, the tree takes on a whitewashed appearance.  As the scale feeds on the tree, they pierce the tissue of the tree leaving an entry point for the nectria fungus to invade.  As the fungus moves in it kills the wood, blocking the flow of sap.  Affected trees decline in health and eventually succumb to the disease within three to six years. It is common for infected trees to break off in heavy winds before dying- a condition commonly referred to as “beech snap”.

American beech (Fagus grandifolia) is the only native species of this genus in North America.  Representing the extreme northern and western range of the species, Michigan has roughly 32 million beech trees that provide an important food source for both people and wildlife.  It has been reported that the disease is responsible for the loss of 2.5 million beech trees to date, and that number is expected to increase as the disease spreads by about six miles a year.

Currently the MIDNR is focusing on reducing infected trees in beech stands to slow the spread of the disease by salvage logging high timber value trees. Private landowners should focus on early detection because prompt treatment is the most effective way to protect beech trees in 
the landscape. However, even early treatment for beech scale may not prevent trees from becoming infected with the fungus that causes beech bark disease.  If certain infested trees cannot be treated their removal will retard the establishment of new infestations.  Because wind and rain can dislodge eggs and crawlers from the tree, washing trees (especially smaller ones) with a strong jet of water periodically from June to November also will reduce infestations of beech scale.  For further information on beech scale and beech bark disease contact your local Conservation District.

Photo Credit:  Bill Cook, MSU Extension.

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