Southern Exposure: Long-Term Field Testing of Wood Protectants

When researchers are looking to evaluate the performance of wood protectants, the harsher the environment the better. Which is why Forest Products Laboratory (FPL) researchers put specimens to the test in the Harrison Experimental Forest (HEF) in Saucier, Mississippi, and have been doing so for 80 years.

Generations of FPL researchers have used the HEF field site for sub-tropical field testing. Here Oscar Blew is rating posts at the HEF (1950’s).

Located about 35 miles north of the Gulf of Mexico, this sub-tropical field site receives about 60 inches of rainfall a year and has a mean temperature of 68 degrees Fahrenheit. The wood decay hazard in this area is rated “severe” according to the American Wood Protection Association Use Class Rating System and there is significant subterranean termite activity. When in ground contact, untreated wood rarely lasts 12 months in the HEF, to which researchers respond “challenge accepted.” Continue reading

Termites of the Frozen Tundra: How Do They Survive?

One look at our snowy landscape in Wisconsin and it would be easy to assume termites couldn’t survive here. These wood-destroying critters are a common concern for people living in warmer climates, but amazingly, certain species of subterranean termites have been introduced and become established in the northern United States and Canada, as well.

map for termite distribution

Simplified map showing distribution of eastern subterranean termites along its northern range. (Only selected populations are shown to highlight major zones of activity.)

Termites’ ability to adapt to a colder climate was studied in the 1970s and 1980s by Forest Products Laboratory (FPL) researcher Glenn Esenther. Today, FPL entomologist Rachel Arango is still fascinated by the phenomenon.

“Insects are poikilothermic, which basically means that body temperature is determined by the external environment,” explains Arango. “So, temperature is a major factor in species distribution.”

Figuring out how certain populations of subterranean termites can tolerate lower temperatures is important for predicting the potential spread and economic impact of termites, as they are already responsible for billions of dollars in damage to structures annually in North America.

Arango and her termite team will directly compare northern and southern populations of eastern subterranean termites in hopes of better understanding how some are able to survive in colder regions. Concurrent tests between Wisconsin and Mississippi populations will include studying basic differences in cold tolerance, behavioral investigations, and research into genetic differences.

“We hope to identify some of the physiological changes that might increase cold tolerance,” says Arango.

Arango expects the research will be beneficial not only for understanding termites, but for broader research into invasive species, as well, particularly as global climate conditions change.

Results are expected by May 2019. For more details on the study, see this Research in Progress report.

Fighting Termites with…Shrimp?

Every year, millions of dollars go towards safeguarding wood against its six-legged nemesis — the termite. Although usually associated with southern United States, research has shown that these wood-munching insects can infect wood as far north as Wisconsin. Among the chemical sprays and concrete barriers used to combat termites are an array of copper-based, anti-termite wood preservatives.

Termites in a laboratory setting.

Unfortunately, in addition being bad for termites, the copper in these preservatives may also be detrimental to the environment. Some researchers have posited that copper-treated wood may also be linked to the destabilization and premature failure of metal fasteners. Environmentally and structurally safe alternatives (that can meet the demands of green construction) are becoming high on the eco-friendly consumer’s priority list.

When formulating these new treatments, researchers at the Forest Products Laboratory (FPL) may need to enlist the help of another ten-legged animal — the shrimp. Chitosan, a compound known to deter wood decay fungi and some species of insects, can be synthesized from chitin, a waste product generated during industrial shrimp processing. In addition to being environmentally friendly, production of this “shrimp cocktail” is relatively inexpensive.

Although chitosan’s effectiveness against termites is currently unknown, a new FPL study, in cooperation with Mississippi State University, hopes to find out just how much chitosan-laden wood termites can handle. After determining how the insects react to different concentrations of compound, researchers will see if the termites adapt to the chitosan, and if they do, attempt to uncover the biological processes underlying these adaptations. This in-depth evaluation will even include studying the DNA and RNA profiles of the termite digestive tract.

termitedigestome

The termite digestive tract. The hindgut portion can host up to 1 billion microbes per termite.

 

The termite gut can contain 10 million to 1 billion microbes per termite. Recent studies have shown that a termite’s diet can influence the composition of this microbe community and the termite’s wood-degrading enzymes. By analyzing the genetic profiles of the microbes as the termites consume the chitosan, researchers hope to better understand expression of protein(s) or protein product(s) that are responsible for any resistance to the compound.

In addition to verifying the utility of chitosan as a termiticide, the 5-year-long project will offer insight into other aspects of wood preservation. The genetic profiles alone will provide future studies with a wealth of knowledge, and shed more light onto the mechanism of wood degradation by termites.

The information could also be used to improve current approaches to wood protection, further our overall understanding of wood conversion to energy, and may assist in the development of future value-added products.

For more information, please see the Research in Progress publication Effect of Chitosan on the Termite Digestome.

 

Detecting Termites from Afar

Bridges, homes, and other wooden structures in remote areas can require the time-consuming task of professionals physically traveling to and from the structures for periodic termite infestation inspections.

Convinced there had to be a better way, researchers from the Forest Products Laboratory (FPL) investigated the use of remote sensing technologies to monitor the structural components of bridges and homes and transmit the findings to the internet cloud for interpretation. Early detection of termite activity could dramatically reduce the costs of remediation and repair.

Termites in a laboratory setting.

Researchers constructed stainless steel tanks to house termite colonies and commodity size dimension lumber members. The tanks were used to survey and test a variety of termite detection systems under laboratory conditions in order to evaluate their usefulness in remote locations in termite-prone areas.

Overall, results indicated that the simplest and cheapest independent  variables to measure and send were: temperature, relative humidity, dew point, and wood moisture content using off-the-shelf, commercially available sensor systems.

Above ground termite bait stations were determined to be the best method of housing the various sensors to permit ease of subsequent baiting if any termite activity was detected.

Researchers conclude that it is feasible and cost effective to remotely monitor valuable wooden structures, like historic covered bridges, against termite infestation and potential structural damage.

For more details on this study, see this report from the proceedings of the 2015 International Research Group Annual Meeting.

Besting the Bug: Termite Tips From FPL

Aside from a few areas, in Wisconsin, thanks to the long, cold winters, termites haven’t presented too many problems. That doesn’t stop researchers from the Forest Products Laboratory (FPL) in Madison, Wisconsin, from researching the best methods of termite control and eradication. Today, FPL employees are working on sophisticated methods of pest control, but here are a few tried-and-true tips from FPL’s Wood Handbook.

Nv2OX60aRmFwjUWt_3lxNsvHPOxrHbg9hn4Iel69rR8,iSImOncvpbBTtgth-Qbkbh78tzqvx6lmAvSwscdOmLE

Termites, viewed under magnification in a laboratory setting. Notice the winged termites that can easily be mistaken for “flying ants”

About 56 species of termites are known in the United States, but they can be grouped into two categories: ground-inhabiting (subterranean) termites and wood-inhabiting (non-subterranean) termites.

Subterranean termites are responsible for most of the damage to wood in the United States, particularly in the South. The hazard of infestation is the greatest beneath buildings without a full basement (i.e. a slab or crawl space) or in any substructure wood component close to the ground.

Subterranean termites will develop their colonies in the moist ground (termites need constant moisture from either the wood they eat or the ground that they nest in) and build tunnels through earth and around obstructions to reach their food source—your home.

In spring, the termites grow wings, fly for a short time, lose their wings, mate, and start new colonies. “Flying ants” can be an indication of a colony, but not all “flying ants” are termites, and so the insects in question should be carefully examined. Another telltale sign of termites are they earthen tubes they build over the surfaces of a foundation or other open area to reach a wood source. Be on the lookout for these little dirt “runways.”

The best protection for wood in areas where subterranean termites are prevalent is to prevent the insects from gaining entry into the building. During construction, make sure that foundations are made of concrete or pressure treated wood. If you use brick, stone or concrete block, only cement mortar should be used, as termites can dig through some types of mortar.

And the more concrete the better—it’s a good idea to cap the foundation with 4 inches of reinforced concrete, ensure any posts supporting floor girders are made of concrete, and ensure basement floors are made of concrete as well. Untreated posts in a basement should rest on concrete piers too.

With a crawl-space type of foundation, wood floor joists should be kept at least 18 inches (and girders 12 inches) from the earth, with a polyethylene vapor barrier covering exposed soil and extending partially up the foundation wall. This will help keep structural members dry. Above ground, gutters, downspouts, and proper grading should be used to keep water away from the structure.

Insecticides can, and should, also be used on soil before a slab is poured. Furthermore, insulation containing cellulose used as a filler in expansion joints should be impregnated with an approved chemical that is toxic to termites. Sealing the top 1/2 inch of the expansion joint with roofing-grade coal-tar pitch also provides effective protection from ground-nesting termites.

The principal method of controlling an existing infestation is to treat the soil adjacent to the foundation walls with a soil insecticide. Contact between the termite colony in the soil and the wood must be broken. You can also block the “runways” from the soil to the wood or repair leaks or drainage problems that keep the structure wet. In any case, professional consultation is required, and homeowners should contact a national pest control operator association.

Unlike superficial problems like mold or mildew, termites can severely weaken a wooden structure. Humans will always build structures where termites live, but by being termite-aware and practicing good construction habits, you stand a better chance of making sure that these pests don’t turn your home into their next lunch.