Tree-Killing Invasive Beetle Advancing in US

Insect Carries a Fungus That Ravages Forests and Threatens Avocado Industry

Two redbay ambrosia beetles on a US dime. Kelsea Young, Clemson University

Discovered near the port of Savannah, Georgia, in 2002, the invasive redbay ambrosia beetle and its symbiotic laurel wilt fungus have already destroyed an estimated 500 million redbay, sassafras, spicebush, camphor, and swamp bay trees.

The beetle–fungus duo also poses an imminent threat to the US and Mexican avocado industries because the fungus is deadly to all plants in the laurel family, which includes avocado trees.

“Laurel wilt has caused widespread and severe levels of redbay mortality in the Southeastern coastal plain,” said the Mississippi Forestry Commission. The ambrosia beetle is “believed to have been introduced in wooden crating material imported through the shipment of goods from its native range in southeast Asia,” the agency noted.

Redbays are small trees that are common in forest understories in the US and worldwide.

According to a Clemson University factsheet on ambrosia beetles, researchers have recently confirmed the beetle's presence as far north as New York’s Long Island, with one expert noting that it “can spread like a fire.” The US Forest Service, which tracks laurel wilt damage, says 312 US counties are currently affected.

The fungus clogs the trees’ water-conducting tissues, causing the trees to dehydrate, wilt, and die within a few weeks. The spread of the fungus is particularly alarming, as 90% of the US avocado supply comes from Mexico, and a significant number of avocado orchards are in California and Florida.

Ramping Up a Response

A typical redbay tree. Santafesandy/iNaturalist

In response to the growing danger, scientists are working on solutions. A team from the University of Florida's Institute of Food and Agricultural Sciences (UF/IFAS) recently secured a $5 million grant to combat the disease. And researchers are looking in Mexico and Guatemala for avocado trees that are naturally resistant to laurel wilt. These initiatives are crucial for protecting the lucrative avocado industry, which fuels long-term economic growth for both the US and Mexico.

With the beetle continuing its march and threatening one of the world’s most popular fruits, the fight against the laurel wilt fungus is more important than ever.