How can copper keep termites at bay?

Termites can destroy your home, but copper may be the answer. See more pictures of hidden home dangers.

If you own a home, or contemplate owning one, just the mention of termites probably sends chills down your spine. They have been called everything from white ants to insect terrorists, but whatever nickname you give them, termites are bad news. They cost U.S. consumers about $5 billion dollars each year and don't show signs of stopping any time soon [source: Environmental Protection Agency].

Although there are more than 2,000 termite species, the varieties most responsible for damage to homes in the United States are subterranean. Because they live underground, they can be inconspicuous until an infestation is pretty advanced. Subterranean termites eat wood from the inside out, so you won't necessarily realize that your wood is being hollowed out through termite activity because they leave the outer layers intact. They're insidious and sneaky, but they aren't invincible.


To raise a line of defense against termites, builders and manufacturers have come up with a number of ingenious ways to protect the wood in your home and shore up openings in your foundation that can let the voracious invaders in. From creating unappetizing or insecticide-impregnated wood products, to devising physical barriers or obstacle courses to thwart the pests, the man versus termite wars continue. One big weapon in the fight is copper.

Copper makes a good biocide. It has applications as an insecticide, algaecide, bactericide and fungicide. Research is being conducted that tests its ability to kill bacteria on common objects that can transfer cold and flu germs, like doorknobs, and it has a good kill rate when used to combat termites.

In the next few pages, we'll take a look at termites and how copper is being used to combat them. First up, let's learn a little more about the enemy.


The Termite Scourge

Termites live in colonies that can number in the hundreds of thousands. They form castes, such as soldiers, workers and reproductives, which have specialized jobs. When a termite group or colony becomes large and well-established, special young, winged termites fly off in spring to start a new colony. This swarm of winged termites can reproduce when they find a suitable location and are sometimes the first sign a homeowner has that there are termites in the vicinity. It takes a number of years for a colony to become large enough to start producing reproductives.

From their nest, subterranean termites create a complex network of tunnels that can spread underground hundreds of feet in any direction. They build tunnels looking for sources of food, typically wood and roots, and when they find a good food source, like your house or garage, they set up shop and start eating.


Even though they can be tough to spot, especially at first, termites do leave signs of their presence. If you think there may be termites in the neighborhood, spring is a great time to keep an eye out. Swarming termites are attracted to light, so check around the exterior lights and windows of your home for discarded wings or dead termites. Reproductives shed their wings when they find new homes. Termite wings are long and slender and can be distinguished from those of flying ants by their size. A termite's wings are longer than its body, while a flying ant's wings are about the same length as its body. Examining any cobwebs on your property for long, slender termite wings is another good way to check for signs that termites are nearby. If you see shed wings inside your home, it's time to call a termite professional.

Another way to identify the presence of termites is to look for stalactites made of dried mud or narrow, long tubes made of mud between your beams or along your foundation. Termites protect themselves from predation by ants and from the elements by building above-ground tunnel shelters to get from place to place when they can't travel underground. These tunnels are between a 1/4 of an inch to an inch wide (6.35 to 25.4 mm) and can be an indication that you have termites. A good way find out if the insects are actively feeding in or near your home is to demolish part of a suspected tunnel and see if they rebuild it [source: Jones].

In the next section, we'll take a look at how copper's bug-busting properties were discovered and how it works to control pests.


Copper: The Bug Buster

One of the first preparations to use copper in the war against pests is called Bordeaux mixture. In 1882, the French botanist Pierre-Marie-Alexis Millardet discovered that vineyard grapes treated with an unappetizing blend of copper sulfate, lime and water to keep thieves away also killed powdery mildew. It was the beginning of a long tradition of using copper as multi-purpose biocide and helped to start a new chapter in the way man controls his environment [source: Encyclopedia Britannica].

The Environmental Protection Agency (EPA) defines a pesticide as a mixture or substance that destroys, repels or mitigates pests. Copper is an inorganic pesticide that works by oxidizing enzymes, lipids and proteins. This can change the normal role of these agents, making them reactive and toxic, or just changing them enough that they can't be used successfully [source: Freeman].


To control termites with copper-based pesticides, wood used in construction is treated with a special chemical cocktail. The other ingredients in this cocktail have changed over the years as we've come to understand their long-term effects on the environment, but copper continues to be a primary ingredient.

On the next page, we'll take a look at some wood preparations that contain copper.


Wood Preparations Treated With Copper

copper mesh screen
Copper mesh screens can foil a termite's attempt to come into your house.

A successful approach to making a house an unappealing food source for termites is by treating the wood used in its construction with a combination of chromium as a binder, copper and arsenic. This lethal cocktail, called chromated copper arsenate (CCA), has been in use since at least the 1940s for outdoor applications, especially where wood comes in contact with the soil. It also has the advantage of being resistant to deterioration due to sun and water exposure, and inhibits the growth of microbial agents like fungus that accelerate wood's decay.

This isn't a perfect solution, though. Termites can still go around treated wood to other edible surfaces, like the wood in your furniture and even your carpeting, or find pockets in CCA-treated wood that don't have high concentrations of the pesticide. CCA is applied using a liquid solution under pressure, and the pesticide isn't always distributed evenly in all woods. There's also a problem with CCA breaking down over time and leaching into the environment. High levels of arsenic and chromium can be dangerous, and even copper in high concentrations can be lethal, particularly in aquatic systems, like ponds and lakes [source: EPA].


As a result, in the United States, CCA has been eliminated as a wood treatment for residential applications and for use in lumber that will come in direct contact with the skin, like playground structures.

As an alternative, lumber for residential use is sometimes treated with Copper Azole (ACQ), a combination of copper and azole as tebuconazole, with other co-biocides. The recipe has changed a couple of times, but the goal is to create a safer and more environmentally friendly wood treatment.

One disadvantage of both CCA- and ACQ-treated wood is that the copper reacts with other metals through electrochemical action, accelerating the oxidizing process in metal fasteners. Because ACQ contains a larger percentage of copper than CCA and doesn't have the anti-corrosive properties of chromium, wood treated with ACQ preparations may be more challenging and expensive to work with.

This isn't the only way copper helps to keep termites away. On the next page, we'll take a look at copper barriers and other interesting blockades that can keep you safe from termites.


Lots More Information

Related HowStuffWorks Articles

  • Berman, Richard C. "The Bug Patrol." Undated. 5/8/09.,,203091,00.html
  • Beyond Pesticides. "Least Toxic Control of Pests." Undated. 5/13/09.
  • Chemistry Explained. "Copper." Undated. 5/4/09.
  • Cornel University - College of Agriculture and Life Sciences. "Organic Insect and Disease Management - Copper Products." Undated. 5/8/09.
  • Dow Agro Sciences. "Facts About Termites." Undated. 5/8/09.
  • Encyclopedia "Pierre-Marie-Alexis Millardet" Undated. 5/12/09.
  • Environmental Protection Agency. " What is a Pesticide?" Undated. 5/15/09.
  • Environmental Protection Agency. "Potential Revision of the Product Performance Test Guidelines, Structural Treatments." 7/7/08. 5/13/09.
  • EPA. "Chromated Copper Arsenate (CCA):
  • Questions & Answers: What You Need to Know About Wood Pressure Treated with Chromated Copper Arsenate (CCA)." 2/02. 5/6/09.
  • EPA. "Chromated Copper Arsenate (CCA): Copper Azole - An Alternative to CCA." Undated. 5/6/09.
  • Florida Department of Agriculture and Consumer Services. "Formosan Subterranean Termite." 7/07. 5/7/09.
  • Freeman, Mike H. Craig R. McIntyre. "A Comprehensive Review of Copper-based Wood Preservatives: With a Focus on New Micronized or Dispersed Copper Systems." Forrest Products Society. 11/08. 5/7/09.
  • Grounds Maintenance. "How Insecticides Work." Undated. 5/8/09.
  • Harby, Karla. "Safe Termite Control." 4/98. 5/4/09.
  • International Timber Solutions. "Preservative Types." Undated. 5/9/09.
  • Jones, Susan C., Ph.D. "Termite Control." Ohio State University Extension Fact Sheet. 1991. 5/6/09.
  • Lebow, Stan, Bessie Woodward, Douglas Crawford, William Abbott. "Resistance of Borax-Copper Treated Wood in Aboveground Exposure to Attack by Formosan Subterranean Termites." 4/05. 5/8/09.
  • McGraw Hill Construction. "Cop-R-Shield." Undated. 5/4/09.
  • National Pesticide Information Center. "County Extension Offices."
  • New South Wales Government. "What are Pesticides and How Do They Work?" Undated. 5/8/09.
  • Outdoor Structures Australia. "Copper Azole Timber Treatment." Undated. 5/6/09.
  • Pest Practice. "Keeping Termites at Bay." Undated. 5/5/09.
  • Reece, Frank. "How to Identify Termites Guide." Undated. 5/10/09.
  • Reuters. "Termite Swarming Season Approaches, Threatens Homeowners." 3/19/09. 5/10/09.
  • Southern Pine by Design. "Fasteners and Connectors." Undated 5/6/09.
  • Toolbase Services. "Termite Protection for Exterior Insulated Foundation System." Undated. 5/8/09.
  • Treated Timber. "What is CCA Treated Timber?" Undated. 5/6/09.
  • U. S. Environmental Protection Agency. "Chromated Copper Arsenate (CCA)." 11/08. 5/5/09.
  • University of California - Agriculture and Natural Resources. "Termintes." 5/01. 5/6/09.
  • University of California Statewide Integrated Pest Management Program. "Bordeaux Mixture." 11/00. 5/8/09.
  • University of Illinois - Sustainable Technology Center. "Chromated Copper Arsenate (CCA) Treated Wood." Undated. 5/6/09.
  • University of Kentucky - Department of Agriculture Cooperative Extension. "Taking a Bite out of Termites." 5/2/08. 5/11/09.
  • Utah Department of Agriculture and Food. "Termites." Undated. 5/12/09.
  • Wise Geek. "What is a Termite Barrier." Undated. 5/4/09.