(Lumber, poles, woodwork and manufactured products) Adults of a round-headed borer, commonly called the old house borer Hylotrupes bajulus, are strong fliers and are attracted to odors from recently processed softwoods (Figure 36). They infest only pine, spruce, or fir when wood moisture content ranges from 30% to 10%. Old house borers do not resemble adult buprestids, but the 1/4 to 3/8-inch oval exit holes, powder in tunnels, and chewing sounds of larvae are very similar and often confused.
Adults emerge during June and July in most locations. Eggs are laid in small cracks on wood surfaces during June through possibly September. In the South a minimum of 2 to 3 years is required from egg laying until adults emerge. Infestations in houses less than 2 years old mean the logs/lumber were infested before construction. Logs infested before treatment may remain infested when non-penetrating chemical treatments allow larvae to survive in untreated log centers. These larvae emerge as adult beetles that chew holes without ingesting treated wood. These beetles may survive to lay eggs in untreated wood exposed in exit holes or in cracks as partially seasoned logs continue to dry. Unless a deeply penetrating treatment has been used, insecticides must be applied to exterior walls either before or with the scheduled water-repellent preservative treatment required for prevention of decay fungi. Insecticide surface treatments will not kill larvae deep in wood and are not recommended for interior surfaces; finishes further limit effectiveness. Injection treatments into exit holes may be effective for limited infestations inside homes. Heavy, widespread infestations may need to be fumigated (Figure 37). Fumigants provide no residual protection, do not penetrate “wet” logs very well, and often fail to control beetles in log houses. But fumigation may give immediate control and is accepted by financial institutions when houses are being sold.
The most important group of insects that attack wood in use other than termites are three closely related families of beetles (Lyctidae or true powderpost beetles, Bostrichidae or false powderpost beetles and Anobiidae the deathwatch beetles). They are all generally referred to as powderpost beetles. The larvae can reduce wood to a mass of powdery or pelleted frass. The damage caused by these 3 families can be identified by the type frass produced as well as types of wood infested (Table 1).
Anobiid beetles naturally occur throughout the South and may attack untreated wood in exterior logs or exposed wood in crawl spaces (Figure 39). About 260 species of anobiids occur in the United States. Wood must have moisture contents above 13% (but preferably below 20%). Pine and yellow poplar are often attacked, but many other hardwoods also are susceptible. Cedar and western softwoods are not attacked by the most common anobiid species in the south. The furniture beetle, Anobium punctatum, attacks only well-seasoned wood that has not been sandpapered, painted or varnished. The female requires a rough side in order to lay eggs. The eastern deathwatch beetle, Hemicoelus carinatus, has been recorded from ash, basswood, maple, beech and elm and in sills, joists, beams and flooring. Attacks by this beetle may be confused with that of a lyctid beetle but its emergence holes will be a little larger and the frass is somewhat coarser (see Table 1). Anobiid infestations in recently processed logs
Powder of anobiids feels gritty and lyctids like talcum powder. Anobiid adults may emerge from infested wood placed in centrally heated or air conditioned spaces, but wood moisture will be too low for survival of small larvae thus reducing the possibility of reinfestation by emerging adults. This is not true for lyctids. Lyctids will often reinfest the wood for many years. To kill lyctids before using infested wood, move wood from 60 to 80ºF temperatures and store at OºF or below for at least 48 hours for 1-inch-thick wood. Bostrichids (false powderpost beetles) differ from the lyctids and anobiids in that they bore into wood to lay eggs instead of ovipositing in surface cracks or pores. The most common bostrichid in the eastern United States is the redshouldered shothole borer, Xylobiops basilaris. It prefers to breed in hickory, persimmon pecan and elm. Infestations of powderpost beetles are often discovered when frass appears on wood surfaces. One should not panic at this stage. Powderpost beetles work slowly often requiring many years for the damage to be severe. If hardwood flooring is infested one should try to determine whether or not the infestation is widespread or just limited to a few boards. Oftentimes replacing a few boards will solve the problem. If the infestation is widespread, the flooring finish can be removed and the boards treated with borates. Since anobiid infestations often occur in pine joists, sills, rafters and subflooring they can often be treated easily with borates. Borates will not penetrate wood surfaces that have been painted or sealed with varnish or acrylic. Such wood surfaces must be sanded before an effective treatment with borates can begin. The two borate formulations that are currently available for use are Bora-Care® and Tim-Bor®. Bora-Care® is recommended for well-seasoned wood and Tim-Bor® for green logs and lumber. |
Forest Pests: Insects, Diseases & Other Damage Agents |
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