I have some very bad news. It concerns two of our most common but easily-overlooked shrubs/small trees: the redbay (Persea borbonia) and sassafras (Sassafras albidum). They don’t directly affect people’s lives, except that sassafras is the source of the flavoring for root beer and gumbo file, and redbay is occasionally used in cooking. They do play a role in the ecosystems of east Texas, and we may be about to receive an unpleasant lesson in the interconnectedness of things.
Just 14 years ago, a small insect, the redbay ambrosia beetle (Xyleborus glabratus), somehow made its way from Asia to Georgia. It carries, and is dependent upon, a fungus: laurel wilt (Raffaelea lauricola). The beetle burrows into members of the Laurel family, which includes redbay and sassafras. In so doing, it infects the tree with the fungus, which kills the tree within a short time. It has had a devastating effect on these species in South Carolina, Georgia and Florida.
Why do we care? Well, do you enjoy seeing the large and lovely Palamedes swallowtails? Or the spicebush swallowtails? In their larval form, they feed exclusively (as far as I know) on members of the laurel family—all susceptible to the laurel wilt. If we lose all the redbay and sassafras, will we lose these magnificent butterflies? And what else would we lose? These swallowtails are major pollinators of the Chapman’s orchid. Are they the only pollinators?
A number of species of birds feed on the fruit of these two species. How important will the impact be on birds if we lose them?
What other species may be dependent on these trees?
What can be done to control laurel wilt? At this point—nothing. Researchers are looking for a solution, for the beetle/fungus duo also attacks a commercially important species—the avocado. The avocado industry is worth millions of dollars to the Florida economy, and according to one estimate, 10% of the tree canopy in Miami-Dade County consists of avocados. There appears to be nothing to stop this plague from spreading though Texas and into Mexico, so if you like your guacamole, wish those researchers luck.
I am guessing that it is the redbay/laurel wilt complex that is killing the redbay trees and the sassafras at Watson Preserve. It has been confirmed in Hardin County, and that is the next county over. There is no barrier to its spread. I’ve seen dead redbays south of Kountze, and between the preserve and the town of Warren. These trees appeared to be healthy this spring—their death has been sudden.
I have lots of questions, but no answers. I shall attempt to find out for sure if this new pest is the cause of death of our redbay and sassafras. I’m betting it is. This is one time I’d like to be wrong. Meanwhile, enjoy the beautiful Palamedes and spicebush swallowtails while you can. They face a fight for survival the likes of which they’ve never seen before.