Granulate Ambrosia Beetle Control

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If you have woody ornamentals and trees in your landscape you may have noticed damage from the granulate ambrosia beetle. This pest was introduced from Asia in the early 1970s. It has since spread throughout the Southeast. An infestation can be identified by toothpick-like strands (or frass) protruding up to 1.5 inches from trunk of the host plant. These strands of boring dust are produced by the female beetle as she begins to excavate her gallery. The strands are fragile and are easily broken off by wind or rain leaving only pencil-lead sized holes. Individual plants may contain from one to hundreds of individual beetles. Ambrosia beetles become active around the first of March in the North Carolina Piedmont and usually peak by early April. Timing is dependent on local weather conditions and beetles can attack trees much earlier during warm spells. Ambrosia beetles remain active through the summer and into the fall. Trees located in nurseries are attacked primarily during the spring but trees within the landscape may be attacked all summer. Females bore into twigs, branches, or small trunks of susceptible hosts. They excavate tunnels in the wood, introduce ambrosia fungus, and lay eggs to produce a brood. It is the growing fungus on which the beetle grubs feed, not the wood.

picture of Adult Granulate Ambrosia beetle

Adult Granulate Ambrosia beetle

picture of Ambrosia Beetle damage to cherry tree.

Ambrosia Beetle damage to cherry tree.

Homeowners have few products available that contain the active ingredients permethrin or bifenthrin that may be sprayed on the trunk. However, these only work as prevention and will not work once the beetle is inside the tree. Whenever you decide to use pesticides be sure to also follow the label and recommended dose. It is best to maintain healthy plants to reduce and outgrow any damage from Ambrosia beetles. For more information on insect pests and other topics please contact Colby Griffin, colby_griffin@ncsu.edu or 919-496-3344.