Searching for Natural Resistance through Infrared Spectroscopy

Closeup view of Western Junipier – By Syntheticmessiah – stock.adobe.com

Durability is one of the most important building qualities needed for timber products. It is measured by how well wood species can resist fungal decay or insect damage.

Some trees are just naturally better at resisting rot.

And as market and public demand increases for more naturally resistant wood that hasn’t been treated with potentially harmful preservatives, researchers are looking to the trees for answers.

That’s what PhD student Shahlinney Lipeh from Forest Research Institute of Malaysia (FRIM) in collaboration with Forest Products Laboratory (FPL) researcher Mark Mankowski and a group of international researchers are looking for through infrared spectroscopy.   

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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

Time in a Bottle: Finding New Life for an Old (Yet Reliable) Test Method

The simple soil bottle presents an extremely useful tool for predicting performance of preservative treated, modified or naturally durable woods. The methodology was developed in the 1940s exclusively for evaluating wood preservatives against wood decay fungi. It has been adapted over several decades to include naturally durable woods, wood plastic composites, and engineered wood products, and we use it constantly here at the Forest Products Laboratory (FPL).

The basic premise of the soil bottle is a material is presented to an actively growing fungus in an otherwise sterile environment. The resistance of the material to fungal degradation is determined by comparison to reference materials (non-durable species or treated reference material). The soil bottle also presents an excellent tool for studying basic fungal biology whereby cellular changes in wood during the decomposition process can be analyzed.  The soil presents a refuge for the decay fungus as well as a source for moisture and transported ions relevant to the decay process.

Past, present and future research at FPL is looking at ways of modifying the standard soil bottle setup to be even more useful for the evaluation of wood and wood protectants. Here are just a few examples of where FPL researchers are pushing the boundaries of the standard soil bottle: Continue reading

Warm, Wet Wood Means Fungi to Follow: Is Your Home a Mushroom Magnet?

fungimap

Climate index for decay hazard. Higher numbers indicate greater hazard.

Fungi are the principal agents of decomposition in ecological systems, and are an unavoidable fact-of-life. Although particularly prevalent in the south, where temperature and humidity create ideal conditions, wherever you find organic matter, fungi will be close behind.

When it comes to wood and wooden structures however, these pint-sized parasites can create big problems, leaving unsightly stains or even weakening buildings to the point of structural failure.

Two kinds of major decay fungi are recognized: brown rot and white rot. With brown-rot fungi, only the cellulose is extensively removed, the wood takes on a browner color, and it can crack across the grain, shrink, collapse, and be crushed into powder.

rot

Representative samples of four common types of fungal growth on wood: (a) mold discoloration; (b) brown rotted pine (note the dark color and cubical checking in the wood); (c) white rot in maple (note the bleached appearance); (d) soft-rotted preservative-treated pine utility pole (note the shallow depth of decay)

With white-rot fungi, both the lignin and cellulose are usually removed, so the wood may lose color and appear whiter than normal. It does not crack across the grain, and until severely degraded, it retains its outward dimensions, does not shrink or collapse, and often feels spongy.

When combating fungi, the temperature and moisture content of the wood are essential to consider.

Most fungal decay can progress rapidly at temperatures that favor the growth of plant life in general. For the most part, decay is relatively slow at temperatures below 50 degrees Fahrenheit and above 95 degrees Fahrenheit. Decay essentially ceases below 35 degrees Fahrenheit or above 100 degrees Fahrenheit.

Serious decay also only occurs when the moisture content of the wood is above the fiber saturation point (about 30 percent). Fully air-dried wood usually will have a moisture content not exceeding 20 percent, and should provide a reasonable margin of safety against fungal damage.

Brown, crumbly rot, is sometimes called dry rot, but the term is incorrect because wood must be damp to decay, but may become dry later. There are also a few dry-rot fungi that have water-conducting strands; such fungi are capable of carrying water (usually from the soil) into buildings or lumber piles.

lifecycle

The decay cycle (top to bottom). Thousands of spores produced in a fungal fruiting body are distributed by wind or insects. On contacting moist, susceptible wood, spores germinate and create new infections in the wood cells. In time, serious decay develops that may be accompanied by formation of new fruiting bodies.

The early stages of decay are often accompanied by a discoloration of the wood, which can be difficult to recognize but is more evident on freshly exposed surfaces of unseasoned wood than on dry wood. Abnormal mottling of the wood color, with either unnatural brown or bleached areas, is often evidence of decay infection.

Late stages of decay are easily recognized, because the wood has undergone definite changes in color and properties. The character of these changes depends on the organism and the substance it removes.

If you see these tell-tale signs of decay on your wooden structures, and cannot dry the wood or turn down the temperature, researchers at the Forest Products Laboratory (FPL) offer these tips for cleaning outdoor surfaces prone to fungi, like your deck or siding. Fungus will always be among us, but detecting it, managing it, and mitigating its damage is well within our control.

For more information, please see Chapter 14 of FPL’s Wood Handbook: Wood as an Engineering Material

Curious Collection: Thousands of Decay Fungi Cataloged at FPL

The Forest Products Laboratory’s (FPL) Center for Mycology Research is home to one of the largest collections of wood-decay fungi in the world. The collection consists of an herbarium and a culture collection.

Photo courtesy of shutterstock.com

Photo courtesy of shutterstock.com

The herbarium serves as a national repository for wood-decay fungi collected by mycologists since the early 1900s. The fungi fruiting bodies (mainly conks, mushrooms, crusts, or stromata) are collected in the field and then dried and briefly frozen for insect control.

The culture collection is one of the largest assemblages of fungi in the world, containing about 12,000 isolates representing about 1,500 species. The collection is diverse, but primarily consists of Basidiomycetous fungi. Mycologists continuously collect new cultures of wood-decay fungi as they conduct research on fungal biodiversity throughout the world. These fungi are brought back to FPL and identified by experts, and cultures of the freshly collected fruiting bodies are made from spores, fungal tissue, or both.

The herbarium and culture collection are a valuable resource to the scientific community. Aside from contributing to further study of fungi through classification or DNA sequencing, the collection is also used in biotech applications. Examples of such work include using decay fungi to break down wood for pulp and paper or biofuels production, and for bioremediation of toxic pollutants in soil.

Wood decay fungi are also a potential source of pharmaceuticals, including cancer-fighting agents. Pharmaceutical companies have screened some of FPL’s fungi for their ability to produce chemicals that may be of use in medicine or other processes. Many opportunities exist for further work in this area.