What caused this small, toothpick-like mass of sawdust to protrude from the trunk of this stressed peach tree?
The small toothpick-like mass of sawdust protruding from the tree is often called a “frass toothpick” or “frass noodle”. The structure was created by an adult female ambrosia beetle (likely Xylosandrus spp.) tunneling into the tree.
Ambrosia beetles are members of nature’s cleanup crew. They typically attack stressed, dying, and dead trees, though some species will attack live, healthy trees. Both native and non-native ambrosia beetles are prevalent in SC. Adults are usually about 1/8 inch long, but some can be up to 1/4 inch long. They range in color from reddish brown to dark black. They are rarely seen because they spend most of their life cycle in galleries burrowed within the tree. When temperatures warm to 70 °F, adult females emerge from an infested tree and find a new tree to invade. The female uses her specialized mandibles to chew into tree bark, through the phloem and into the xylem, where she continues forming a gallery (tunnel). As the female burrows, she pushes excrement and wood particles out of the entrance hole, which sticks together and forms toothpick-like structures. The entrance holes are perfectly round and about 2 mm wide. As the female excavates the gallery, she also introduces fungal spores, which rub off her body and onto the insides of the gallery. The fungi grows inside the gallery and serves as a food source for her future brood. The ambrosia fungi help break down the wood.
After the gallery is ready and the fungus has colonized the walls, the female lays a mass of tiny, white, translucent eggs. The size of the egg mass is dependent on the gallery space and the amount of “ambrosia
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