During the past week, I have heard two reports of what is apparently Asian ambrosia beetle.  Infestations by this insect can be identified by toothpick-like strands protruding up to 1.5 inches from the host plant. These strands of boring dust are produced by the female beetle as she excavates her gallery.  In many cases this insect results in the death of vulnerable young trees, and our control options are very limited.

This beetle is a serious pest of both ornamental and fruit trees, especially those with thin bark or trees that are damaged, stressed, or recently transplanted.  They also attack otherwise healthy trees.  Plants reported to have been damaged include styrax, ornamental cherry, pecan, peach, plum, cherry, persimmon, Japanese maple, golden rain tree, dogwood, sweet gum, Shumard oak, Chinese elm, magnolia, fig, azalea, and others.

Female beetles bore into the sapwood of young tree trunks or branches, usually from 1 to 2 ˝ inches in diameter.  Symptoms include wilting foliage and strands of boring dust projecting from boring holes.  See picture at  http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note111/infested.gif   These strands of dust often project directly out from the stem.  Boring holes are about the size of a pencil lead, perhaps slightly smaller.

Infested plants or plant parts often need to be removed.  But wait.  Entomologists currently think it’s better to leave the infested plant in place for 3 to 4 weeks.  Current thinking is that by leaving the affected plant, it acts as a decoy or trap for other beetles in the area, possibly protecting other trees from attack. 

Once trees are infested the insect cannot be killed within the plant.  There are few pesticide alternatives.  Once a tree is attacked, it MAY be possible to protect nearby trees with an insecticide spray.  This approach involves putting a protective insecticide on the trunk and lower branches to prevent infestation.  This type of protection will last a few weeks at best, depending on the nature of the product and the environmental conditions.

Potentially effective products include pyrethroid insecticides containing active ingredients such as permethrin or cyfluthrin.  Because of changing ingredients in certain brands, it is difficult to give you a brand name that you can look for.  If you choose the insecticide approach, you will need to take your glasses and look carefully at the label for “active ingredients” and make sure that the product gives directions that include the use you need.  For example, the label should specify if it is suitable for use on food crops (fruit trees) or ornamental trees.

For more information on Asian ambrosia beetle, consult the insect note at  http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note111/note111.html or call your Extension office for a copy.

Recommendations for the use of chemicals are included for your convenience.  The use of brand names and any mention or listing of commercial products or services does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any, chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.