Forest Pests: Insects, Diseases & Other Damage Agents

Bark Beetles and Weevils Ambrosia Beetles Forest Health Guide for Georgia Foresters Written by Terry Price, Georgia Forestry Commission Adapted for the web by the Bugwood Network

(Coleoptera: Scolytidae, Platypodidae)

There are many species of ambrosia beetles in the families Scolytidae and Platypodidae. Only a few are considered to be note worthy in the South. Some will breed in living trees but most prefer dying or recently cut trees, logs, and pulpwood. The principal ambrosia beetle that infests southern pines is Platypus flavicornis (Figure 1). This species will infest weakened, dying, or freshly cut pines and unseasoned pine lumber. It bores into the sapwood and heartwood of logs or lumber and makes hundreds of pin-size holes; each stained with fungal growth. The fungus is generally referred to as ambrosia and serves as food for the larvae and adults. The wood is not eaten. All species of ambrosia beetles require wood with moisture content of at least 48 percent.

Figure 1 photo by Tom Hall

P. flavicornis is a common insect that is attracted to pines recently attacked by bark beetles. Piles of whitish boring dust (frass) around a tree’s base indicate an ambrosia beetle infestation (Figure 2). The pinholes created by ambrosia beetles can degrade log and lumber values (Figure 3). Prompt utilization of dead and dying trees and rapid drying of lumber can reduce losses from this ambrosia beetle. Decked logs can be protected from attack by installation of water-misting systems.

Figure 2 photo by Terry Price

Figure 3 photo from USDA Forest Service - Wood Products Insect Lab Archives

Other species of Platypus ambrosia beetles breed in hardwoods, particularly oaks, poplar, beech, hickory, pecan, elm, sweetgum, and magnolia.

Adult ambrosia beetles sometimes attack erected log houses, particularly when the logs are rewetted or are freshly finished with stains that contain alcoholic solvents that attract these beetles. Offspring rarely survive from such attacks.

Another ambrosia beetle common in the South is the Columbian timber beetle Corthylus columbianus (Figure 4). Unlike P. flavicornis this beetle attacks healthy and weakened trees. Species preferred are yellow poplar, sycamore, maple, oak, elm and beech. Trees weakened by flooding are also attacked. This beetle degrades lumber by its boring and its introduction of a fungus that stains the wood. Silvicultural practices that promote tree vigor and the rapid utilization of damaged trees are essential in managing the Columbian timber beetle.

Figure 4 - Pupae and callow adult photo by Jack C. Nord

Figure 5 photo by G. Keith Douce

The black twig borer, Xylosandrus compactus, has established itself as a major twig-infesting insect in the South. It will infest a broad range of tree species including dogwood, holly, magnolia, sweetgum and oak. The adult beetles measure about 1/15 of an inch in length. Recently transplanted trees are most susceptible. Infested twigs should be pruned and destroyed as soon as possible.

The Asian ambrosia beetle, X. crassiusculus, has become established throughout much of the South. This beetle attacks a wide range of hosts including magnolia, sweetgum, cherry, persimmon, pecan and oak. Long strands of frass are often seen sticking out from infested trees (Figure 5).

There is no practical chemical control for X. crassiusculus and X. compactus. Infested plants or plant parts should be cut and burned.

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