Laurel wilt pest begins to spread into Georgetown County

GEORGETOWN, SC - Laurel wilt, a disease which sounds the death knell for redbay trees wherever it appears, has spread to yet another coastal SC county, Georgetown.

Researchers with the South Carolina Forestry Commission (aided by lab staff of the USDA Forest Service) say laurel wilt’s movement is having a devastating impact not only on redbays, but possibly other plants in the laurel family.

Redbay are ecologically and culturally important to the South.  The tree is ubiquitous across coastal urban and suburban landscapes.

And it’s the tree of choice for the caterpillar of the Palamedes swallowtail, a very large black and yellow butterfly which depends entirely on redbays to complete its lifecycle.  Laurel wilt’s impact on the butterfly, however, has yet to be determined.

Ironically, insect preferences are at the center of the problem.  Laurel wilt is delivered by the non-native redbay ambrosia beetle (Xyleborus glabratus).  Its female bores through the bark of the tree carrying a fungus on her mouthparts.

Once the beetle is inside the tree, she carves out tunnels in which she’ll lay eggs.  The fungal spores grow in these tunnels, blocking the movement of water from the tree roots causing the tree to wilt and eventually die.

The fungus is extremely fast-acting and trees typically die within a month after being infected.

Before its appearance in Georgetown County, laurel wilt was known to be killing redbays in twelve other (mainly coastal) South Carolina counties, according to Forestry Commission entomologist Laurie Reid.

“We’re pretty sure the insect and its fungal companion spread geographically when infested wood, often in the form of firewood, is transported by humans,” Reid says.

So, homeowners with dead redbay trees are encouraged to keep the wood waste on their property.  They can help slow the spread of laurel wilt by cutting, chipping, or burning (in accordance with state and local laws) the wood on-site.

Experts hope these measures will slow the spread of laurel wilt across the American Southeast.  It’s been found in 30 counties in Georgia and 31 in Florida, but so far very few in North Carolina, Alabama, and Mississippi,

“Simply put, dead trees should not be transported off-site to a landfill or taken elsewhere to be used as firewood,” the Commission’s Reid warns.

Symptoms of laurel wilt include drooping reddish or purplish foliage.  Evidence of ambrosia beetle attack can be found in the trunk.  Often strings of chewed wood, called toothpicks, can be seen sticking out of the entry holes.  Removing the bark from a tree suspected of having died from laurel wilt will reveal black streaking on the outer wood.

Symptoms like these tipped off the staff of Hobcaw Barony, a wildlife refuge owned by the Belle W. Baruch Foundation. 

Death of redbays there are a teaching opportunity for the research-oriented site and something they are prepared for, according to George Chastain, Executive Director.

“With our focus on research and conservation (at Hobcaw Barony), we are keenly aware of the impacts non-natives are having on our forest and marshes.  Invasive plants, animals, insects and diseases continue to alter our ecology and threaten native species,” Chastain says.  “The spread of laurel wilt is just one example of the many challenges we face as natural resource managers.”

Camphor and sassafras trees, part of the laurel family, are suffering sporadically too on the 17,500-acre institute’s land, giving Georgetown Co. the dubious distinction as the thirteenth county to which laurel wilt has spread in South Carolina.