How Big Is a Formosan Colony, and How Far Does It Forage?

What does the Extension brochure say about colony size?

The brochure says a Formosan colony can hold several million termites. That is a very large number for a subterranean colony, and it means the treatment has to reach a population that is far bigger than the damage a homeowner can see.

The brochure is careful with its numbers. It describes a colony that can reach several million termites, and it presents that as a characteristic of the species rather than a claim about any particular house. The number explains why a light treatment on the damage often fails to hold.

A large population also means the colony can absorb losses. Workers that are reached by a treatment are replaced by others from the same nest, so a plan that kills the visible workers without reaching the rest of the colony can look successful for a while and then fail.

This is the basis for the monitoring advice. The inspector cannot count the colony, but the record of activity over time shows whether the treatment is reaching it.

How far can foraging workers travel?

The brochure says foraging workers can forage up to 300 feet from the nest. That is well beyond the footprint of a typical lot, which means a colony can feed through a neighbor's tree line or a stump on the next property.

Foraging distance is the number that changes how a homeowner should think about the yard. Three hundred feet can carry workers from the back of a lot to the front of a house, or into the next yard, and the path is often a root or a buried stump rather than an open route.

That distance also explains why a neighbor's problem can become a homeowner's problem. A colony that is established on one lot can reach a house on the next one, and the homeowner has no control over the neighbor's trees. The best a homeowner can do is check their own lot and keep their own structure clear.

For the inspection, the distance means the lot cannot be read from the house alone. The technician checks the trees, the stumps and the fence line, because those are where the foraging routes begin and end.

• Check the trees and stumps on the lot, not only the house.
• Look at the fence line where it meets the house.
• Note any neighbor's tree or stump that touches the property line.
• Record the routes found, not only the damage.

How do nests split between buildings and trees affect the plan?

The Extension brochure says Formosan nests are split between buildings and trees. A plan that treats only the house leaves the tree part of the colony working, so the trees on the lot are included in the inspection and, where needed, in the treatment.

A split nest is a colony that uses more than one place. A tree can hold a nest chamber, and the house can hold another, with workers moving between them along roots or under the soil. Treating one and ignoring the other leaves the colony intact.

The plan should therefore name the tree zone as a separate item. A bait station in the root zone, a soil treatment around the root collar, or the removal of a dead stump are options. Removing a live tree is a separate decision for the homeowner and an arborist.

The monitoring should follow the same split. Stations are read in the yard, the house is re-inspected, and the trees are checked for new activity. A record that covers both sides is the one that shows whether the colony is still using the lot.

Why does a single treatment often disappoint?

A single treatment reaches the workers and routes it can see at the time, and a large colony with a 300-foot foraging range can use routes that were not treated. The disappointment is usually a sign that the plan did not cover the whole colony, not that the product failed.

A treatment is a point in time. It acts on the routes that were found and treated, and it does not reach a route that was hidden, a tree that was not inspected or a neighbor's stump. A colony that finds an untreated route will use it.

Workers that were not reached are not the only issue. Some workers may be in a wall void or a tree at the time of the treatment, and they continue to forage after the product has been applied. The result can look like a failure when the real issue is incomplete coverage.

The fix is a plan that names the routes, treats each one, and returns to check. The monitoring then shows whether the colony has stopped using the routes it was using, and that is the measure of success.

What should a homeowner expect a plan to say about colony size?

A plan should say what the inspection found, which routes the colony uses, what was treated, what could not be reached and when the next check is due. It should not claim to have counted or eliminated the colony, because the sourced record says the species is not eradicated once established.

A plan that claims the colony has been eliminated on the day of treatment is making a claim the Extension record does not support. A better plan describes the routes and the checks, and it says what would show the treatment is not holding.

The plan should also say which parts of the lot were not reached. A fenced area, a neighbor's stump or a locked crawlspace is a gap that the homeowner should know about, and the next visit should address it if access can be arranged.

Finally, the plan should set the monitoring intervals and the triggers for an earlier visit. A homeowner who knows the triggers can act on them, and a plan that lists them is the one that keeps working through the year.

• The routes the colony uses, with locations.
• The treatments applied to each route.
• The areas that could not be reached.
• The monitoring dates and the triggers for an earlier visit.

What does this mean for a Riverside or Avondale home?

Riverside is the place the Extension brochure names for Formosan concentration, and Avondale is adjacent. A home there should be planned with the colony's size and reach in mind, and the trees and older framing should be part of the check from the start.

The concentration finding is not a verdict on a house, but it is a reason to plan for a large colony with a long reach. The homeowner should expect the inspection to include the trees, the stumps and the fence line as well as the framing.

The older housing in these neighborhoods has its own routes, such as brick joints, porch joints and sills set on masonry. Those are points where the colony can reach the structure, and the plan should cover them.

A homeowner in these neighborhoods should keep the monitoring schedule going after the first treatment. The Extension finding that the species is not eradicated once established is the reason the schedule matters more here than it might elsewhere.