Saturday, June 29, 2019

An update: red bay trees that died back from laurel wilt disease in 2008.

Three months before the red bay tree by the
pond turned brown, seemingly overnight,
two pileated woodpeckers gave warning
that bugs were infesting the tree.


Back in 2008, we were shocked when all the red bay trees (Persea borbonia) in our yard suddenly turned totally brown. One day they looked fine, the next day their leaves were all dead. After doing some research, I found that the cause for this was the laurel wilt disease, which was carried by the redbay ambrosia beetle, a tiny insect that entered this country in pallet wood from Asia in Savannah, Georgia in 2004. The beetle carries a fungus that blocks the xylem cells so the water stops flowing through the trees. This is why the symptoms are so sudden, because without the flow of water, the tree cannot function. The fungal disease is known as the laurel wilt disease. Other members of the Laurel family (Lauraeae) that are susceptible to this disease include both natives such as sassafras and spicebush, and non-natives such as avocado and camphortree. Here is a link to the article I wrote back then: Red Bay Trees are Dying.

2008. A red bay out in the front meadow died.
2008. A tree on the west bank of the pond died back. 2008. A red bay out back died back. We weren't aware that it was out there until it suddenly turned brown.

After eleven years, it's time for an update

Well, there are still red bay trees that have been sprouting since 2008, which is fortunate for the two butterfly species that depend upon this plant as their primary larval food source here in northern Florida, palamedes swallowtail (Papilio palamedes) and spicebush swallowtail (Papilio troilus). But after a couple of years, most of them die back again.
Yes, our red bays are still larval host plants. Note the new growth that is stimulated after so much of the leaf has been eaten.  At least some of these leaves had been eaten before this sucker died back.

One red bay is twenty feet tall


But maybe there's hope for the future of this wonderful tree, because one red bay is twenty feet tall, has a girth of about two inches at ground level, and has fruit. Maybe it has immunity to the laurel wilt disease or maybe it was just over looked by the beetles so far. I hope it survives because it has developed immunity and all its offspring will be immune as well.
The top of this 20-foot tall red bay looks lush. 
One red bay has grown much larger than the suckers that sprout, but then die back in a year or two. Is this tree a hope for the future of a red bay comeback or just lucky for now? This red bay has matured enough to produce fruit.

"You don't know what you've got 'til it's gone..." —Joni Mitchell


Before this disease hit, I had not been really aware of the red bays. I didn't appreciate that its evergreen leaves were fragrant, or how much it added to the habitat areas in the yard. I look forward to a day when Mother Nature will bounce back with new immunity from this Asian invader.

So Carpe Diem and learn to appreciate the nature in your yard every day possible, because you never know what's in the future.

Green Gardening Matters,
Ginny Stibolt

For more background on Laurel Wilt and the Redbay Ambrosia Beetle, click this link: Biology, Ecology, and Management of Laurel Wilt and the Redbay Ambrosia Beetle

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