What role does copper play in keeping termites away?

If you're a homeowner or thinking about owning one, the mere thought of termites probably sends a shiver down your spine. Often referred to as 'white ants' or even 'insect terrorists,' termites are a serious concern. They are responsible for approximately $5 billion in damages annually in the U.S. and their impact shows no sign of slowing down [source: Environmental Protection Agency].

Though there are over 2,000 species of termites, it's the subterranean varieties that cause the most damage to U.S. homes. Since these termites live underground, they can go unnoticed until an infestation has already caused significant damage. Subterranean termites consume wood from the inside out, so the outer layers might appear unaffected while the interior is being eaten away. Sneaky and destructive, they’re not unbeatable, however.

To defend against termites, builders and manufacturers have devised several innovative methods to safeguard the wood in your home and seal potential entry points in your foundation. From producing wood that’s unappealing to termites or infused with insecticides, to creating physical barriers or challenges to hinder the pests, the battle between humans and termites rages on. A powerful tool in this ongoing fight is copper.

Copper serves as an effective biocide. It has multiple uses as an insecticide, algaecide, bactericide, and fungicide. Ongoing studies are exploring its potential to eliminate bacteria on commonly touched surfaces, like doorknobs, which spread cold and flu germs. Copper also boasts a high efficacy rate in exterminating termites.

In the following pages, we’ll explore termites and how copper is being utilized in the battle against them. But first, let’s get to know the enemy a little better.

The Termite Menace

Termites live in vast colonies, sometimes numbering in the hundreds of thousands. These colonies have distinct castes—soldiers, workers, and reproductives—each with specialized roles. As a colony grows and matures, certain young termites with wings take flight in the spring to establish new colonies. These swarming winged termites are often the first indication a homeowner might have that termites are nearby. It can take several years before a colony produces reproductives.

Subterranean termites construct intricate tunnels that can extend underground for hundreds of feet in any direction. These tunnels are created as they search for food sources, mainly wood and plant roots. Once they locate a desirable food source, like your house or garage, they settle in and begin feeding.

Although they can be hard to detect, especially early on, termites leave behind clear signs of their presence. Spring is an ideal time to stay vigilant if you suspect termites nearby. Swarming termites are drawn to light, so check around outdoor lights and windows for discarded wings or dead termites. When reproductives find a new location, they shed their wings. Termite wings are longer than their bodies, unlike flying ants whose wings are about the same length as their body. Another good tip is to examine cobwebs for long, slender termite wings. If you find shed wings inside your home, it’s time to call a termite expert.

You can also spot termites by looking for mud-like stalactites or long, narrow mud tubes along your foundation or beams. To protect themselves from ants and the environment, termites build these above-ground shelters to travel between locations when they can't move underground. These tubes, ranging from 1/4 inch to 1 inch (6.35 to 25.4 mm) wide, are a telltale sign of termites. A quick way to check if the termites are still active is to break a section of a suspected tunnel and see if it’s rebuilt [source: Jones].

Next, we’ll explore the discovery of copper’s pest-killing properties and how it works to combat infestations.

Copper: The Ultimate Pest Fighter

One of the earliest uses of copper in pest control is known as Bordeaux mixture. In 1882, the French botanist Pierre-Marie-Alexis Millardet discovered that treating grapevines with a blend of copper sulfate, lime, and water, originally intended to deter thieves, also effectively killed powdery mildew. This marked the beginning of copper's long history as a versatile biocide and ushered in a new era of environmental control [source: Encyclopedia Britannica].

The Environmental Protection Agency (EPA) defines a pesticide as any substance or mixture designed to destroy, repel, or manage pests. Copper is an inorganic pesticide that works by oxidizing enzymes, lipids, and proteins, altering their normal functions, rendering them toxic or reactive, or simply preventing them from performing their intended roles [source: Freeman].

To fight termites with copper-based pesticides, construction wood is treated with a specialized chemical blend. Over the years, the additional ingredients in this mixture have evolved as we’ve gained more knowledge about their environmental impact, but copper remains a key component.

In the following section, we’ll examine some wood treatments that incorporate copper to protect against pests.

Wood Treatments Infused with Copper

One effective method to make a home unattractive to termites is by treating the wood used in construction with a mix of chromium as a binder, copper, and arsenic. This powerful combination, known as chromated copper arsenate (CCA), has been utilized since the 1940s, particularly for outdoor wood applications, especially where wood meets soil. It also offers resistance to deterioration caused by sunlight and moisture, while inhibiting the growth of microorganisms like fungi that contribute to wood decay.

This isn’t a foolproof method. Termites can bypass treated wood and target other accessible food sources, such as the wood in your furniture or even your carpets, or find untreated pockets in CCA-treated wood where the pesticide concentration is lower. CCA is applied through a pressurized liquid solution, but it doesn't always distribute evenly throughout the wood. Additionally, CCA degrades over time and leaches into the environment, which can be a concern. Arsenic and chromium levels can be harmful, and even copper in excessive amounts can be toxic, especially in aquatic ecosystems like ponds and lakes [source: EPA].

As a result, CCA has been banned in the United States for residential wood treatment and for lumber that comes into direct contact with skin, such as in playground equipment.

As a safer alternative, residential lumber is often treated with Copper Azole (ACQ), a mixture of copper and azole compounds like tebuconazole, along with other biocides. The formulation has evolved over time, with the aim of creating a more environmentally friendly and less toxic wood treatment.

One downside to both CCA and ACQ-treated wood is that copper reacts with other metals through electrochemical processes, accelerating rusting in metal fasteners. Because ACQ has a higher copper content than CCA and lacks chromium’s anti-corrosive properties, wood treated with ACQ can be more difficult and costly to work with.

But copper isn't just effective in wood treatment for termites. In the next section, we'll explore copper barriers and other innovative solutions that can keep termites at bay.