How to Tell Whether a Drywood Termite Fumigation Failed

It’s rare, really, really rare that a drywood termite fumigation fails to kill all the drywood termites currently infesting a structure. So why might someone continue to find termite frass (a.k.a. termite pellets, droppings, excrement) one month, two months, or two years after a successful termite fumigation?

It helps to understand what drywood termite activity and damage looks like. As drywood termites consume wood, they create long tunnels, called galleries, running with the grain of the wood. Over time, the galleries get filled with the undigested  parts of wood–termite pellets. At some point, the drywood termites will create a kick-out hole in the wood surface and clear the pellets out of the galleries to enable movement. The kick-out hole is small, typically the size of a dot left by a felt pen. Because thousands of pellets may be ejected one by one from the same small hole, pellet piles from an active colony are usually conical, not scattered.

Termite Pellet Mound

Drywood Termite Pellets

Even after a drywood termite colony is exterminated, billions of termite pellets may remain in termite galleries inside the wood of a home. Unless all the damaged wood is removed and replaced, expect some drywood termite pellets to succumb to gravity and filter down over time.

This video shows a piece of wood pulled from a house after a drywood termite fumigation. The wood was heavily damaged by drywood termites and some of the galleries were only 1/32 of an inch below the surface of the wood. Some of the galleries were breached simply through the act of removing the damaged wood from the structure. Note how the galleries were filled with drywood termite pellets.

Read with Caution: Extreme Ick Factor

Another reason piles of termite pellets may appear after a successful fumigation is…ants. It’s rare, but sometimes garden ants will move into the termite galleries to feast on the dead termites. In the process they move termite pellets out of the way. If this is the cause of the sudden appearance of termite pellets, nothing needs to be done. The ants will clean up the termite carcasses and move on. They do not typically take up long-term residence.

Knowing this, what is a homeowner to do about termite pellets discovered after the drywood termite fumigation?

First, immediately after the fumigation either the property owner or the termite company needs to remove or mask* (that is, cover up with non-toxic powder) all visible termite pellets, especially those in difficult to access areas, such as the attic or crawlspace. Why? Because it is impossible to tell whether termite pellets are fresh or years old. By removing or masking all visible termite pellets after the fumigation, later on it will be easier to identify any newly deposited pellets associated with a new infestation.

Additionally, termite pellets or frass discovered within a month after fumigation should be cleared away. They are most likely left over from the newly exterminated termite colony. Make a note of the location of the termite pellets.

If the termite pellets were near a door or a window, vibrations from opening and closing the door or window may be causing the pellets to filter out of the now empty termite galleries. In this situation, pellets may filter out for some time.

New piles of termite pellets found in locations not subject to vibrations are more of a concern. Consult with your termite company.

Termite pellets or frass discovered more that a month after fumigation do not necessarily mean a failed fumigation; however, go ahead and call your termite company. They will have valuable insight about your property that can set your fears at ease or they will inspect the area of concern.

 *Expect to compensate the termite company for masking the termite pellets. It is dirty, but necessary work to mask pellets in a crawlspace or attic.