Southern Lyctus Beetles
Order:
Coleoptera
Family: Lyctidae
Scientific Name: Lyctus planicollis LeConte
The Southern lyctus beetle, Lyctus planicollis, is found throughout the United States and Mexico. The lyctid powderpost beetles are commonly referred to as the true powderpost beetles when comparing them to the anobiids (death-watch or furniture beetles). They are classified as wood-destroying insects and are the most destructive beetles to hardwoods; however, they are considered less important than anobiids in terms of their destruction of wood in homes.
Lyctids are usually brought into structures in wood that contains their eggs and larvae. They usually infest the wood while it is either drying or in storage, prior to installation. Typically, they are found in hardwood floors, timbers, and plywood, as well as hardwood articles such as crates, furniture, antiques, and tool handles.
These black-colored beetles are 1/5” (5mm) long, with the males being much smaller than the females. The general body shape is long, narrow, and flattened, with sides being relatively parallel. The pronotum, which along with the mandibles is visible from above, is distinctly wider just behind the head. The antennae have a two-segmented club, with the last segment being wider than long. The elytra (wing covers) have rows of fine setae (hairs).
The mature whitish larvae are “C”-shaped and often less than ¼ inch (6mm) in length. They have three pairs of legs, and the thorax is distinctly larger than the rest of the body. The spiracle on the last abdominal segment is three times larger than any of the other abdominal spiracles.
Biology and Habits
This species attacks only the sapwood of hardwoods (oak, hickory, and ash). The female deposits 15-50 eggs deep into exposed wood pores. The incubation period is 1-3 weeks, at which time the newly hatched larvae tunnel along the grain of the wood. As the larvae molt and mature, they tend to meander through the wood, but never break through the surface layer.
Normal larval development requires 2-9 months depending on the wood’s moisture content (10 to 20 percent is ideal), starch content, and temperature. After pupation (12-30 days), emerging adults bore immediately to the surface and out of the wood. The entire life cycle is usually 9-12 months. However, under less favorable conditions, it may require 2 ½ to 4 years.
Adults
are most abundant in late winter to early spring.
During the day, adults hide in cracks and holes in the wood.
At night, however, they are active fliers and are attracted to
light, which is why they can often be found on window sills.
Control
Signs of infestation include the appearance of small round exit holes 1/32” to 1/16” (0.8 – 1.6 mm) in diameter in infested wood. More compelling evidence is the accumulation of piles of flour-like wood powder (frass) near these adult emergence holes. Determining whether an infestation is active is often the most difficult task. This can be accomplished by knocking out all loose frass and marking existing exit holes, and then reinspecting the wood 1-2 months later for frass and additional holes.
Beetle reinfestation can be prevented by finishing the wood with varnish, paint, shellac, sealer or wax. This seals the pores and cracks in the wood surface used by the female for oviposition.
Nonchemical controls include reducing wood-moisture content below 10 percent and storing wood at lower temperatures. Heat can be used in some situations; however, its success is determined by temperature, humidity and time. Physical removal of infested wood is an option when the infestation is limited, and the wood is accessible.
Several residual insecticides are available for direct wood treatment. However, such applications are limited when the wood has been finished. The newest residual products contain sodium octaborate tetrahydrate, which can provide a greater degree of wood penetration depending on the wood-moisture content.
If
properly performed, fumigation is the best method of ensuring that the
infestation has been eliminated.
(Courtesy of the National Pest Control Association.)