How can copper keep termites at bay?

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.

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.

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.