Old house borers attack softwoods only -- coniferous woods such as pine, fir, spruce and hemlock. It usually attacks stored lumber, after which the wood destroying beetle is introduced into homes as they are built. Log homes infested with old house borers is a very common occurrence.
The Old House Borer belongs to the beetle family Cerambycidae, a group also known as the "long horned" beetles. The key identifying characteristic of this family is long, thin antennae that ore often as long (or longer) than the body of the beetle. The adult old house borer can be from 5/8 inch to 1 inch in length, with the males typically being smaller than their female counterparts. The beetle's body has a slightly flattened appearance. Its color may appear dark gray, but is usually brownish black to black. The prothorax (behind the head) is rounded in shape and contains two raised, shiny black "bumps." The wing covers of the old house borer are black, with lighter gray colored areas forming bands that are usually present about one-half down the wing covers. Yellowish-gray hairs may be present on the head and the prothorax. It is not often that a homeowner (or pest control operator) actually finds adult old house borers in a structure. As will be explained later in this article, the sound of the larvae feeding inside timbers, exit holes and frass are the signs that point to an actual infestation.
The head of the old house borer larvae is round and is much larger than its tail, a shape which is typical of the Cerambycidae beetles which are known as "round headed borers." This larvae is grayish-white in color and grows from 3/4 inch to 1 5/8 inch in length. The head capsule is dark brown, and three simple eyes are found on each side of the head when viewed from the front. This characteristic sets the old house borer larvae apart from other long horned beetle larvae found infesting wood. Other long horned beetle larvae have only one such eye on each side of the head. The frass of the old house borer consists of very fine powder and tiny pellets that are tightly packed within the galleries. The holes of the larvae are oval shaped. This oval exit hole and the appearance of frass are usually the first indications of old house borer infestations.
Old house borer larvae feed until they reach about 200 mg. in weight. At this time, the mature larva tunnels to the surface of the wood and cuts an oval shaped exit hole. This exit hole is then sealed with packed frass. Just below this exit hole is a pupal chamber where the larva pupate. Even after emerging from the pupal stage, the adult beetle may remain in the pupal chamber for up to 10 months. The oval exit hole created by the emerging adult old house borer can be 1/4 inch to 3/8 inch in diameter.
Treatment for Old House Borers (Boracare, Jecta Gel, Fumigation)
In managing old house borer infestations, single pieces of lumber, furniture and the structure itself are treated in the same manner as treating for powderpost beetles. Unpainted wood should be treated with Boracare or injected with Jecta Gel. Surface treatments of Boracare may not always penetrate deep enough to kill all existing beetle larvae, meaning that new exit holes may still appear after application. Boracare and Jecta Gel will prevent re-infestation of timbers and furniture.
In cases of severe beetle infestation, a professional should be called on to fumigate the structure. After fumigation, a surface treatment of Boracare should be applied to prevent re-infestations of old house borers, powderpost beetles and other wood destroying pests.
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