There are several types of larvae that damage wood in trees, lumber, furniture and homes. The most common are termites, powderpost beetles, round-headed borers and flat-headed borers. Wood-boring larvae primarily injure trees already weakened by severe stress factors, such as disease and storm damage. The wood-boring larvae are rarely seen, as they live their entire lives inside the wood.
Identify the boring cavity. For example, If it is oblong, it's the flatheaded wood borer. If metal such as steel or wire is pierced, its the lead-cable borer.
Identify the adult insect that will often visibly emerge from the boring cavity after it pupates. Then, you can tell which larvae are found inside.
Observe the grub directly by cutting through the wood to expose the channel, if the cutting will not do further damage. Larvae are much more similar in appearance to one another than in the adult stages. For example, roundheaded wood borer larvae resemble a grub found in your lawn or compost pile and termite larvae resemble a miniature version of the adult.
Identify the larvae by the boring dust or frass created. For example, powderpost larvae create white fine, dust-like powder resembling talcum powder or baking flour: Termite larvae create pepper-like pellets with ridges on their sides; and false powderpost larvae leave coarse powder similar to powdered borax soap.
Identify the larvae by the type of wood. For example, powderpost beetles attack hardwoods with high starch content and low moisture content: Deathwatch beetles primarily infest softwoods with high moisture content, especially Douglas-fir; and false powderpost prefer wine barrels.
Emerging winged adult wood-boring beetles found near or in homes tend to fly toward light, so you'll typically find dead adults on windowsills after they have tried to disperse. Wood-boring larvae are difficult to control because they are protected within the tree during most of their lives. Pruning dead or infested wood from trees helps prevent destructive borer populations. Insecticide applications for wood-borers should be made just prior to the appearance of the adult.
Before using any insecticide, read the label carefully for directions on application procedures, appropriate rate, first aid, storage and disposal. Make sure that the chemical is properly registered for use on the intended pest.