Sassafras and Laurel Wilt Disease

sassafras
Two swallowtail butterfly species strongly prefer to lay their eggs on sassafras. Illustration by John Abbott, 1797. Courtesy of Wikimedia Commons.

The scent of a crushed sassafras leaf is unforgettable – sweet, pungent, fragrant. If you have never plucked one of the leaves and rolled it around between your fingers, you should.

“Sassafras is susceptible to laurel wilt disease,” says U.S. Forest Service research mathematical statistician KaDonna Randolph. “The disease has not reached the heart of the sassafras range, but it is spreading throughout the Southeast.”

A nonnative fungus-beetle duo causes laurel wilt disease. The beetle, known as the redbay ambrosia beetle, has mandibular mycangia – pockets of fungus in its mouth. The fungus that causes laurel wilt disease can survive in these pockets.

When redbay ambrosia beetles tunnel into healthy trees to lay eggs, the fungus is unleashed. It invades the trees’ vascular system and can kill the tree within a few weeks. Laurel wilt disease affects all members of the laurel family – sassafras, redbay, swamp bay, pondberry, and avocado.

Randolph studied sassafras and laurel wilt disease across the Southeast. Her study was published in the Southeastern Naturalist and uses data from the Forest Inventory and Analysis unit. FIA monitors plant communities across the U.S., and historically focused on timber resources. Timber is still a priority, but FIA also collects data on invasive plants, soil properties, lichens, carbon storage, and non-timber species such as sassafras.

Listen to a brief audio clip by author KaDonna Randolph describing this publication. • Text Transcript

The data showed that by 2014, almost 2 billion sassafras trees and saplings grew in the U.S. across 28 states. Most of the counties where sassafras grows are not infected with laurel wilt disease.

Less than 2 percent of sassafras trees grew in counties where laurel wilt disease had been detected. Less than 3 percent of trees were located next to a county with laurel wilt disease.

“Currently, less than 5 percent of sassafras trees are exposed to laurel wilt disease,” says Randolph. “However, the disease can be devastating – some studies have found that more than 80 percent of sassafras died within three years of the disease being detected.”

foliage
Sassafras leaves can be shaped like mittens, a trident, or an oval – and all three leaf shapes can be found on the same branch. Illustration by Franz Eugen Köhler, 1897. Courtesy of Wikimedia Commons.

Laurel wilt disease has been spreading slowly through Georgia and other states in the coastal plain since at least 2002. However, it has made discontinuous leaps to Alabama, Arkansas, and Louisiana. If such a leap brought the disease to the interior eastern U.S., it could devastate sassafras and permanently change forests.

“Landowners and forest managers within the range of sassafras should be diligent,” says Randolph. “Watch for laurel wilt disease and consider the changes that may occur in forests if it becomes established.”

Should laurel wilt disease make that deadly leap, Randolph’s study will function as a benchmark for sassafras health and keep us from forgetting what was lost.

Read the full text of the article.

For more information, email KaDonna Randolph at krandolph@fs.fed.us.

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