Subterranean termites live in the ground and are the most common and destructive pests of wooden structures. These insects require constant contact with soil or a moisture source to survive, allowing them to tunnel unseen toward cellulose-containing materials. Dealing with these pests effectively without resorting to synthetic pesticides requires a strategic, multi-faceted approach focused on natural treatments and environmental modification. This guide explores non-chemical solutions to manage and eliminate termites found in the soil surrounding your property.
Harnessing Beneficial Nematodes
Biological control offers one of the most targeted and environmentally friendly methods for soil-dwelling pests, utilizing beneficial nematodes. These are microscopic, non-segmented roundworms that naturally occur in soil environments worldwide. The species most effective against subterranean termites are the entomopathogenic nematodes, particularly those from the genera Steinernema and Heterorhabditis.
These nematodes are considered obligate parasites, meaning they require an insect host to complete their life cycle. They actively seek out termite larvae, pupae, and workers in the soil, entering the pest through natural body openings like the mouth or anus. Once inside the termite, the nematode releases symbiotic bacteria, which multiplies rapidly and causes septicemia, killing the host within 24 to 48 hours.
For successful application, the soil temperature must be consistently above 52°F, but ideally between 50°F and 85°F, to ensure the nematodes are active. Nematodes are vulnerable to ultraviolet light, so they should be applied outdoors during the early morning, late evening, or on a cloudy day to prevent desiccation. The application area must be pre-watered until the soil is moist, as nematodes require a film of water to move and locate their prey, and the soil should be kept moist for up to two weeks following treatment.
Nematodes are typically shipped on a sponge or in a powder and must be mixed with water to create a liquid solution for application using a watering can or hose-end sprayer. They pose no threat to plants, pets, humans, or non-target beneficial organisms like earthworms and ladybugs, making them a safe component of an integrated pest management plan.
Applying Physical Barriers and Desiccants
Physical methods work by either creating an impenetrable layer termites cannot tunnel through or by desiccating the insects upon contact. Diatomaceous Earth (DE) is the most common natural desiccant used for direct-contact control in soil. DE is a fine powder composed of the fossilized remains of diatoms, which are single-celled algae with silica-rich outer shells.
The mechanism of action is purely physical, not chemical; the microscopic, sharp edges of the DE particles abrade the protective waxy layer of the termite’s exoskeleton upon contact. This damage causes the insect to lose moisture rapidly, leading to fatal dehydration. To apply DE in the soil, it should be worked into the topsoil or trenched around the affected area, ensuring the product remains dry since moisture significantly reduces its effectiveness.
In addition to desiccants, physical barriers provide a long-term, non-toxic defense against subterranean termites from the soil. Specialized termite-grade sands or stainless steel mesh can be installed around foundations or vulnerable areas to create an impenetrable zone. Termites struggle to move through sand of a specific particle size, and the mesh forms a complete barrier that they cannot chew through or bypass, blocking their access to the structure.
Using Botanical Oils and Extracts
Botanical oils and extracts offer a naturally derived alternative that can be used to treat localized termite activity in the soil. These plant-based solutions often contain compounds that are toxic or repellent to the pests. Two of the most effective options are Neem Oil and Orange Oil, which contains d-Limonene.
Neem oil, derived from the seeds of the neem tree, contains azadirachtin, a compound that acts as an insect growth regulator and antifeedant. When termites consume wood or soil treated with neem oil, it disrupts their feeding behavior, growth, and reproductive cycles. For soil application, a concentrated, emulsified neem oil product is diluted with water to create a soil drench, ensuring the solution penetrates the termite tunnels and nesting sites.
Orange oil relies on the active ingredient d-Limonene, which is extracted from citrus rinds and is toxic to termites on contact. This compound works by dissolving the waxy coating of the termite’s exoskeleton, leading to rapid dehydration and death. To create an effective soil drench, the orange oil must be emulsified before being diluted with water, then poured directly into the soil where termite activity is detected. Since these oils require direct contact or ingestion to be effective, repeated applications are often necessary to affect the entire colony structure beneath the ground.
Long-Term Prevention Through Soil Management
Shifting the focus from active elimination to passive prevention is a sustainable strategy that involves modifying the soil environment to make it inhospitable to termites. Subterranean termites require high levels of moisture for survival, which means improving drainage around any structure is a primary defense. Proper grading of the soil should slope away from the foundation to prevent water accumulation near the building perimeter.
Maintaining clean gutters and downspouts ensures that rainwater is directed several feet away from the foundation, reducing soil saturation. Addressing any plumbing or roof leaks immediately also prevents localized moisture pockets in the soil that termites find attractive. Reducing soil moisture eliminates the necessary habitat for termites, forcing them to forage elsewhere.
The removal of cellulose-containing materials from direct contact with the soil is another necessary step, as termites feed on cellulose. This includes ensuring that wood piles, lumber, or old tree stumps are not resting directly on the ground near the home. Additionally, a buffer zone of non-cellulose material, such as gravel, crushed rock, or sand, should be maintained around the foundation, replacing mulch or soil that would otherwise provide a food source and easy tunneling access.