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Weekly “What is it?”: Swamp bay

 

The galls on swamp bay leaves are caused by small insects called psyllids. While unsightly, they are not harmful to the plant. Photo credit: Carrie Stevenson, UF IFAS Extension

Swamp bay (Persea palustris) trees are among my favorites. After working in wetlands for years and observing the fascinating adaptations that plants must make to thrive there, I have a soft spot for wetland species. Swamp bays are super easy to recognize in the wild, too, because their leaves are almost always full of galls. The galls are created by a type of small flying insect called a psyllid (Trioza magnolia). The leaves are curled up because an adult psyllid lays eggs on the leaves, and the developing larvae roll the leaves around themselves to form a sort of cocoon. While the galls disfigure swamp bays and aren’t their most beautiful feature, they do not harm the tree. These galls are so common that their presence is an easy way to identify the tree and differentiate it from the similar red bay.

Swamp bays are common in wet forested areas, but are dwindling in number due to laurel wilt disease. Photo credit: Carrie Stevenson, UF IFAS Extension

There are a number of tree species that go by the common name, “bay” tree—from sweet bay magnolias (Magnolia virginiana) and bay laurel (Laurus nobilis) to swamp and red bays (Persea borbonia)— but they are different species. All being in the laurel family, though, they do have similarities; particularly in their growth habitat and scented leaves, which have culinary uses. The bay leaves you buy in the spice section of the grocery store are typically bay laurel, while local cooks often pick leaves from nearby sweet or red bay trees to flavor soups and gumbo.

Swamp and red bays are related to the avocado, all of which have fallen prey in the last decade to a disease called laurel wilt.  Laurel wilt is a fungal disease caused by an exotic species of ambrosia beetle. Damage from this disease has killed many of our native red bays in the southeastern US, moving outward from their accidental introduction in south Georgia almost 20 years ago.