Subterranean Termites in Arizona: How to Spot Mud Tubes Before They Reach Your Drywall

The way to spot subterranean termites before they reach your drywall is to look for mud tubes on the outside of the foundation, on the garage slab joint and around plumbing under sinks, because those tubes are the covered highways the colony builds between the soil and the wood, and they appear weeks or months before any damage shows inside.

How Desert Subterranean Termites Live

The desert subterranean termite (Heterotermes aureus) is the termite under most of the low desert in Arizona, from Yuma through the Phoenix metro to Tucson. The colony lives in the soil, often several feet down, and it never exposes itself to open air and sunlight if it can avoid it. To reach the wood in a house it builds mud tubes, pencil to finger width tunnels made of soil, saliva and droppings, up the foundation and into the structure. Inside the tube the workers move back and forth between the soil moisture and the wood they are eating.

Arizona is one of the highest termite pressure regions in the country because the soil is warm year round, the colonies are large, and nearly every house is slab on grade with stucco over frame or block, which puts wood a few inches from soil. Irrigation makes it worse. A drip line running against the stem wall, a citrus basin against the house or a flood irrigated lot keeps the soil at the foundation damp all year, and that is exactly where the colony forages.

Where the Tubes Show Up First

Termites take the shortest covered route from soil to wood, so the tubes appear in a handful of predictable places.

• The stem wall on the outside of the house, especially where stucco meets the slab and where a drip line or hose bib keeps the soil wet. Look for a thin brown line running up from the dirt.

• The garage expansion joint, the crack between the garage slab and the stem wall along the inside of the garage, usually behind the water heater and the washer where nobody looks.

• Plumbing penetrations under the kitchen sink, bathroom sinks, the tub trap access and behind the water heater, where the drain and supply lines come up through the slab.

• Interior block walls and stem walls behind drywall, where the tube runs up the block inside the wall and the first sign is a small mud spot or a bubble in the paint at the baseboard.

• Wood in contact with soil: a patio post, a fence post against the house, a wood planter, a stack of firewood.

The tube does not have to be long. A 3 inch tube on the garage joint is enough to reach the bottom plate of the wall. Old dry tubes that crumble to dust with no workers inside mean past activity that may or may not have been treated. A tube that is damp and rebuilds within a day or two after you break a section off is live.

What the Damage Looks Like Inside

By the time termites show inside, the tube has been there a while. The signs are small: a pinhole in the drywall with a speck of mud at it, a line of mud along the top of a baseboard, paint that bubbles or looks water damaged where there has been no water, a door frame that sounds hollow when tapped, or a soft spot in a wood floor. In older homes with wood windows and door frames the frames get hollowed from the inside. Swarmers, the winged reproductives, show up in spring and after monsoon rain, and a pile of shed wings on a window sill is a colony inside or right next to the house.

How to Check Your Own House

Once or twice a year, and any time you notice a mud spot, do a slow walk with a flashlight.

1. Walk the outside of the house at the slab line and look at the stucco base and the stem wall for brown tubes, especially near drip lines, hose bibs and the AC condensate drain.

1. Open the garage and look along the expansion joint behind the water heater and washer, and along the garage to house wall.

1. Open every sink cabinet and the tub access panel and look where the pipes enter the slab.

1. Tap baseboards and door frames and press on any bubbled paint.

1. Check any wood touching soil around the house.

If you find a tube, leave it. Breaking it all off removes the evidence the inspector needs to confirm live activity, and it does not hurt the colony.

What Treatment Involves

A subterranean termite treatment in Arizona is a liquid termiticide trench and treat around the whole foundation, with holes drilled through the garage slab, patios and walkways so the product reaches the soil under the concrete where a trench cannot go. A non repellent product such as fipronil lets workers walk through it and carry it back to the colony. Where trenching is not practical, bait stations go in the ground. Live tubes inside the wall get foam. Every treatment is reported to the Arizona Department of Agriculture on a Termite Action Report Form and the homeowner keeps a copy with the warranty. The single biggest thing a homeowner can do after treatment is move the drip line 18 inches off the stem wall so the soil there dries out.

Termites do not bite or spread disease, but they are the one Arizona pest that damages the structure, and a colony left alone for years costs far more in framing repair than any treatment. A home sale with a termite report that finds live tubes also stalls until treatment is done and a clearance is issued.

FAQ

Can I treat a mud tube myself with a hardware store spray? You can kill the workers in that tube. The colony in the soil is untouched and builds a new tube a foot away. A perimeter treatment that reaches the soil is what stops it.

How fast do termites eat through a house? Slowly. A colony may take years to do serious damage, which is why the tubes are worth catching early and why a yearly check is enough for most homes.

Does a termite treatment last forever? No. A properly applied liquid treatment protects a home for several years, and the annual reinspection under the warranty catches any breach before the tubes reach drywall.

If you found a tube on the stem wall or the garage joint, leave it in place and book a termite treatment inspection with Green Ninja Pest Control so the activity can be confirmed and treated before it reaches the framing.