Ambrosia Beetles

By Kenton Shepard

Ambrosia beetles are small beetles, averaging around 1/8” or less, depending on species. They typically infest live and freshly-cut hardwood and softwood trees. Their excavations are not a structural problem.

Two species of Ambrosia beetle

Life Cycle

In early spring they bore a primary tunnel into trees or fresh logs for a short distance before branching off into secondary tunnels in which the eggs are laid twice a year, March and October. From hatching to emerging as adults takes 7 – 10 weeks.

Source

Main tunnel with secondary egg chambers

They don’t feed on wood, but on fungi ("ambrosia") which grow on the walls of the tunnels which are inoculated with the fungi by the beetles. Several generations may continue to extend the galleries as long as the tree retains sufficient moisture for the growth of fungi. The fungi stain wood and problems with ambrosia beetles are cosmetic.

Courtesy of Permachink Inc. 

Fungal stains from Ambrosia beetle infestation

INSPECTION CONCERNS

Newly emerging adults exit through  the original entry hole. Small hole size and staining define Ambrosia beetle infestation.