Ambrosia Beetles Are Behind Those Tubes

ambrosia beetle frass tubes

Sawdust tubes pushed out by ambrosia beetles as they bore into a tree. Photo: E. Nibali

Q: These things like spaghetti pasta were sticking out of our tree that suddenly died. They crumbled when I touched them. Did they attack the tree and kill it?

A: These are sawdust tubes pushed out by ambrosia beetles as they bore into your tree. The tubes are rarely seen this time of year. However, because of abnormal rainfall, some trees are producing ethyl alcohol, a reaction to stress. Alcohol production signals ambrosia beetles to attack. The beetles introduce a fungus into the tree, which clogs up its xylem (the water and nutrient transport system). Since your tree is already dead, it’s hard to say exactly what killed it. Its roots may have rotted or drowned from standing water or saturated, poorly draining soil. The ambrosia beetles may have merely pushed it over the edge. The beetles are not necessarily a death sentence. When numbers are low and a tree is fairly healthy, a tree can recover.

Learn more about ambrosia beetles on the Home & Garden Information Center website.

By Ellen Nibali, Horticulturist, University of Maryland Extension Home & Garden Information Center. Ellen writes the Garden Q&A for The Baltimore Sun.

Have a plant or pest question? University of Maryland Extension’s experts have answers! Send your questions and photos to Ask an Expert.

4 Comments on “Ambrosia Beetles Are Behind Those Tubes

  1. Ambrosia beetle is what was initially blamed for the SODS (Sudden Oak Death Syndrome) that killed so many tan oaks and coast live oaks since the mid 1990s. They were just secondary pathogens that infested trees that were already infested with Phytophthora ramorum.

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  2. I had always wondered what these were, I never thought it was beetles digging into the tree…is there a special repellent to keep these certain beetles away?

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    • These beetles are attracted to stressed trees so, it is important to maintain good tree health to the extent that you can. Provide adequate water during dry periods, don’t over-mulch, and take steps to avoid physical injuries to the tree (mower, string trimmer damage). We do not recommend a repellent.

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