GRANULATE [ASIAN] AMBROSIA BEETLE TRAPPING
CAUTION This information was developed for North Carolina and may not apply to other areas.
THE GRANULATE [ASIAN] AMBROSIA BEETLE Xylosandrus crassiusculus (Mot.), Coleoptera, Scolytidae (or Curculionidae, tribe Scolytini)
This tiny beetle is a pest of woody ornamental, fruit and nut trees throughout North Carolina and can cause significant damage in nursery and orchard settings. Asian ambrosia beetles have many reported hosts. Among the most common are styrax, ornamental cherry, pecan, peach, plum, cherry, persimmon, Japanese maple, golden rain tree, dogwood, sweet gum, Shumard oak, Chinese elm, magnolia, fig, and azalea.
Female beetles bore into the sapwood of stems and young trees. Although attracted to damaged, stressed, or transplanted trees, this beetle will also attack seemingly healthy, thin-barked hardwoods or branches usually from 1-2 inches in diameter. Visible symptoms include wilted foliage and strands of boring dust protruding from small holes. Heavy infestations may result in tree death (which usually occurs during leafing-out stage).
In areas with a history of Asian ambrosia beetle damage, protective sprays have been the best means of protection. Scouting and trap monitoring are important. Use of ethyl alcohol traps can indicate when beetle flight begins in the early spring. Protective sprays may be applied soon after beetles appear in traps even though beetle captures in traps peak later in the season. Traps do not catch enough beetles to prevent plant damage and are only a monitoring device. An estimate is to use two traps for an acre and one additional trap per acre, but fewer traps could be used.
Commercial traps are available, but homemade traps in several designs offer a useful alternative. For a study comparing trap designs, link here (p.158). Below is a design from James Baker of NC State University. It uses a two liter inverted soft drink bottle mounted about three feet above the ground on a wooden tomato stake. Traps are typically placed around the outside of susceptible plant blocks in a nursery. Be sure to use only ethyl alcohol (ethanol) in the trap. They should be in place by February in some areas and should be checked every two or three days.
For links on the biology and control of Asian ambrosia beetle,
Lacking a specific lure for this beetle, these ethanol traps may also collect other species of beetles.
Also helpful may be the Texas A&M key to female Xylosandrus
ambrosia beetle is attracted to ethyl alcohol traps along with other
bark beetles. Nurserymen need to
be able to distinguish the Asian ambrosia beetle from these other beetles to help make treatment decisions.
The following diagrams are useful in making this determination. They are not intended as a key for identifying other
species of bark beetle, but may help you determine the genera of Xyleborus and Xyleborinus. At least 15x magnification
will be needed to see these features.
Bark beetles are found in the family Scolytidae.The Asian ambrosia beetle is in the tribe Xyleborini and genus Xylosandrus.
on middle and hind leg broadly widened, evenly curved outside edge, with
many teeth. … Xyleborini (go to 2)
1’) Tibia on second and third leg straight or slightly widened, and with few or no teeth… (something else)
2 )Front coxae separated …. Xylosandrus (go to a or b below)
a) rear end surface dull when dry… Xylosandrus crassiusculus (Granulate
[Asian] Ambrosia Beetle)
b) rear end surface shiny when dry…(something else)
2’)Front coxae touching … (go to 3)
3 )Scutellum triangular, flat… Xyleborus
3’)Scutellum conical, pointed…Xyleborinus