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Wood-Boring Beetles Not the Primary Cause of Sugarberry Mortality

dying-sugarberry-tree
This dying sugarberry tree in North Augusta, South Carolina has a sparse canopy and branch dieback. Photo by Michael Ulyshen, USFS.

In the past decade, sugarberry trees (Celtis laevigata) have been rapidly declining throughout South Carolina and Georgia.

Alongside University of Georgia researcher Emilee Poole, USDA Forest Service scientists Scott Horn, Michael Ulyshen, and others studied the distribution and biology of the wood-boring beetle Agrilus macer to determine its role in recent sugarberry mortality.

Using sugarberry samples from southewestern South Carolina, the scientists investigated the distribution and abundance of A. macer egg masses within trees. They also isolated fungal samples from beetle attack sites. The beetle’s known range was determined by reviewing museum specimens throughout North America.

The team found A. macer to be widely distributed throughout the Southeast, with the highest densities in Texas and Louisiana. Before the recent mortality event, A. macer was unknown to Georgia and had not been recorded in South Carolina since 1934.

“It’s incredible to learn that a beetle nobody knew existed in a certain place is so common,” says Horn. “These findings make solving a mystery like this so exciting.”

The researchers learned that the fungi associated with A. macer larval galleries did not significantly impact tree health. This suggests that the beetle is a secondary pest on sugarberry trees. The primary cause of mortality is still unknown.

Read the article in the Annals of Forest Science. This factsheet produced by Clemson University Cooperative Extension includes more information on sugarberry and the borer.

For more information, email Scott Horn at scott.horn@usda.gov or Michael Ulyshen at michael.d.ulyshen@usda.gov.

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