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(News article for March 2020)
Have you noticed toothpick like growths sticking out of the trunk of your tree? These are caused by granulate ambrosia beetles, Xylosandrus crassiusculus, and those “toothpicks” are columns of beetle frass.
The granulate ambrosia beetles (GAB) is a small, wood boring beetle that can be devastating to landscape trees and fruit trees. As they bore into the tree, they inoculate the tunnels with fungi to feed their larvae. The fungi, rather than the beetle tunnels, are what damages the tree. Once you start seeing the frass columns protruding out of the trunk, it is too late. Larger trees can handle GAB infestations, but small trees probably won’t make it.
Young trees and stressed trees are more likely to become infested with GAB so the best control measure is to keep your trees as healthy as possible and protect them from physical damage. Trees with smooth bark and potted trees seem to be more susceptible. If you notice GAB on one of your trees, you can try spraying a pyrethroid insecticide (bifenthrin, permethrin, etc.) on surrounding trees to prevent further infestation. Heavily infested trees should be removed and burned.
Resource
Layton, B. (2020) Granulate ambrosia beetle. Bug’s Eye View, Vol 6, No. 3. Mississippi State University.
Jessie Hoover is a County Agent with the LSU AgCenter covering horticulture in East Feliciana, West Feliciana, St. Helena, and Tangipahoa parishes. For more information on these or related topics contact Jessie at 225-683-3101 or visit The LSU AgCenter Website.
Photos of granulate ambrosia beetle frass columns sticking out of a fig tree.
The LSU AgCenter and the LSU College of Agriculture