Nature Lab

Each month, we highlight research MDC uses to improve fish, forest, and wildlife management.

Forest Pest Management

Laurel Wilt

Missouri’s beloved sassafras trees face a new threat. Laurel wilt — an invasive, tree-killing disease — has been found within 10 miles of the state’s southeastern border in western Tennessee.

“This disease kills sassafras as well as its close relatives — spicebush and the federally-endangered pondberry,” said MDC Forest Entomologist Robbie Doerhoff.

Laurel wilt is a lethal vascular wilt disease that rapidly kills entire clumps of sassafras and its relatives. The disease is spread to new areas when the tiny, wood-boring redbay ambrosia beetle (Xyleborus glabratus) deposits spores of the fungus Raffaelea lauricola in healthy trees.

“Because nearby sassafras trees are often connected underground through root grafts, you might see entire clumps of wilted or dead sassafras as laurel wilt spreads through the roots,” Doerhoff said. “Leaves may cling to affected trees for months after death.”

Other signs to look for are dark staining in the sapwood under the bark and tiny ambrosia beetle exit holes in the bark.

“Please be on the lookout for laurel wilt this summer,” Doerhoff urged. Email photos of dying sassafras, include the location, to Forest.Health@mdc.mo.gov.

Laurel Wilt at a Glance

Cause

The redbay ambrosia beetle (Xyleborus glabratus) and the fungus it carries, Raffaelea lauricola, are native to Asia. Scientists suspect the beetles first entered the U.S. around 2002 through a major shipping port in Georgia.

Treatment

None for infected trees, although research on preventative treatments is underway. Dead and dying trees should be destroyed to slow further spread of the disease.

Ecological Impact

Spicebush swallowtails and other insects, as well as many kinds of birds and mammals, use sassafras, spicebush, and pondberry as food and/or host plants.

Look for These Signs

• Sassafras leaves that rapidly wilt and turn reddish-brown in mid-to-late summer
• Entire clumps of wilted or dead sassafras trees
• Tiny exit holes in the bark
• Dark staining in the sapwood

Learn more at short.mdc.mo.gov/Zzx