New Bug Wants to Kill Your Trees
Pray that you never discover this sight in your garden – weird, little things that look like toothpicks sticking out of the trunks and branches of your trees. Because if you do, your trees are in big trouble.
These "toothpicks" are actually small columns of sawdust pushed out by an insect that bores into trees called the Asian ambrosia beetle (aka granulate ambrosia beetle). First reported in the Carolinas in the 1970s, this Asian invader has spread throughout the Southeast and Gulf Coast. It targets many of our most cherished trees – crepe myrtle, Japanese maple, flowering cherry, redbud, pecan, and many fruit trees. It's bad news, Grumpiana.
How It Kills
The small female beetle, above, bores into the tree to excavate a gallery to lay her eggs. But the holes don't kill the trees. What does is the ambrosia fungus she brings into the tree to cultivate and feed her young. Over time, the fungus spreads and clogs up the tree's vascular system, preventing the transport of nutrients and water. The tree wilts and dies.
Protecting Your Trees
Anecdotal evidence suggests that Asian ambrosia beetles prefer trees that are stressed from drought or another cause or have injuries to the bark. It therefore makes sense to keep your trees healthy and vigorous. Because Asian ambrosia beetles become active in early spring, applying a long-lasting insecticide, such as Ortho Home Defense or Spectracide Triazicide, to the trunks and branches in February may help. Follow label directions carefully, keeping in mind that these products are toxic to bees and fish. Spray again in May.
Once the beetles get inside your tree, no insecticide can reach them. If there are only a few and your tree is otherwise healthy, it may outgrow the fungus and survive. However, once you see dozens of "toothpicks" sticking out like in the photo up top, it's likely curtains for your tree. Cut off all infested branches. Cut to the ground all infested trunks. Burn the wood or put it out with the trash.