Naturalist Fact: Redbay Ambrosia Beetle

Redbay ambrosia beetle (Xyleborus glabratus)

The redbay ambrosia beetle is an invasive pest first detected in 2002 near Savannah’s Port Wentworth. Originating in Asia, this tiny beetle (2 mm) is thought to have been introduced via infested wooden packing materials at the port. Like several other invasive species, this ambrosia beetle has spread quickly and its effects can now be seen on redbay trees throughout the Georgia Coast and into Florida and South Carolina.

Fungus introduced to redbay trees by the invasive ambrosia beetle causes laurel wilt in the tree.

Unlike native ambrosia beetles, this beetle attacks healthy redbay trees by boring into the wood just under the bark, creating galleries in the sapwood where it will lay its eggs. However, it is not the boring, or even the beetles themselves that will kill the tree. The female carries spores of a fungus (Raffaelea lauricola) in a pouch in her mouth which she inoculates into the sapwood as she bores. The developing and adult beetles feed on the fungus while the fungus grows within the tree. As the fungus grows, it blocks water and nutrient movement within the tree, causing laurel wilt and eventually, the death of the redbay tree.

As you explore the maritime forest here on Little St. Simons Island, you will see sapling redbay trees, with the majority of their leaves brown with wilt. Currently, scientists have not found a method of fighting back against the redbay ambrosia beetle. As the beetle and fungus spread, the redbay could be affected across its entire range. An important host plant to three species of swallowtail butterflies, a decline in the redbay could also mean hardships for palamedes, Schaus, and spicebush swallowtails in the coming years.

For more on the palamedes swallowtail, read our previous Naturalist Fact of the Week.

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Naturalist Fact: Palamedes Swallowtail

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The Palamedes Swallowtail belongs to the Swallowtail butterfly family (Papilionadae) of which several members are common in the Southeast. The Palamedes Swallowtail is restricted to the Atlantic Coastal Plain, and adults can be found nectaring in suburban gardens, along roadsides, and in moist wooded areas.

It is one of the larger butterflies in the area with a wingspan of 3.5 to 5.5 inches. Its black wings are decorated with a yellow band running across the wing and yellow spots along the margin of the wing. It also has two blue hindwing eyespots ringed with black and a splash of orange, which distinguishes it from the similar Black Swallowtail.

Unlike most other swallowtails, the Palamedes Swallowtail is restricted to a single host plant—the Red Bay tree (Persea borbonia). The female is known to lay eggs only on this tree, usually a single egg is laid upon a new-growth leaf.

Unfortunately, the Red Bay populations along the South Carolina coast, Georgia coast, and into Florida are in serious decline due to an invasive ambrosia beetle (Xyleborus glabratus) that is believed to have been introduced via the port at Savannah in 2002.

For more info on the Red Bay and the red bay ambrosia beetle, stay tuned for the next Naturalist Fact of the Week!

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