Now You See ’Em . . .

The ghost ant (Tapinoma melanocephalum) is one of a growing number of invasive pests in the U.S. and Canada. Tropical in origin, this ant is now a major pest in Florida, Hawaii, Puerto Rico and the Caribbean Islands. It also is a pest in coastal areas of Texas. In these warm locations, it infests indoors and outdoors.

But you’re not immune if you work in other areas. Infestations of ghost ants have been found inside heated buildings in many U.S. states, and as far north as Manitoba, Canada. It seems likely that many indoor ghost ant infestations in colder climates are missed because the ants are being misidentified as odorous house ants, Pharaoh ants and other small ants.

Ghost ants are tiny “one-node” ants, about 1/16-inch long, smaller even than Pharaoh ants. They are so-named because of their unique coloration: the head and thorax are black (hence the species name: melano = black; cephalum = head) but the rest of the body is transparent. When a ghost ant walks across a light-colored surface, all you see is its dark head and thorax, while on a dark surface you see a pale, ghost-like shape. The ants tend to move erratically. Their “ghost like” bodies are especially difficult to see in low light. Workers have the smell of rotting coconuts when crushed.

BIOLOGY & DISPERSAL. The ghost ant is considered a “tramp ant” — an ant with the proven ability to hitchhike around the globe. Colonies are transported in commercial shipments of house plants, fresh produce and cut flowers. People also unknowingly carry ghost ants home in luggage, clothing and all kinds of household goods, including laptop computers.

A colony can be large and can consist of many small individual nests, each with 100 to 1,000 workers and multiple queens. Workers sometimes move from one nest to the other following odor trails.

Ghost ant colonies spread locally by budding. Queens often simply walk to a new nest site accompanied by a group of workers. They move readily, sometimes nesting in a site for only a few weeks. Like Pharaoh ants, ghost ants can end up with many small nests throughout a building, particularly if disturbed by ineffective insecticide sprays.

Ghost ants are omnivores, meaning they eat almost anything: dead and live insects, human food waste, pet food and especially sweets. Fond of honeydew, they tend insects like aphids that feed on plant juices. Ghost ants often trail to a water source.

INSPECTION & CONTROL. In tropical and subtropical climates, such as Florida, the ghost ant usually forages inside from outdoor nests in hollow cavities in branches, at the base of palm fronds, in plant stems, clumps of dried grass, in bromeliads, under bark, in logs, under flagstones and in flower pots. In the north, the largest infestations have been found in large indoor tropical-style plantscapes, such as those found in some malls and hotels. But they also have been found infesting apartments, homes, and medical facilities, very much like Pharaoh ants.

Ghost ants often are found trailing on kitchen counters, along baseboards and under carpet edges. Once you find an ant trail, follow it back to locate the nest or an entry point into the building. The nest can be generally found in wall voids, behind baseboards, behind cabinets, in potted plants, between books and in many of the same sites you might find Pharaoh ants.

The ghost ant often will be found in bathrooms and near water pipes or A/C lines looking for water. Outdoors, trails of ghost ants can be found along the foundation wall and running up the walls to holes or cracks through which they enter the building. Ghost ants often come up through the slab from below.

CONTROL TIPS. Options indoors include one or more of the following:

• Tracking the ants to find and treat the nest(s).
• Spraying ant trails, hiding places, active areas, and potential entry points with a nonrepellent residual insecticide spray.
• Placing liquid or gel sugar baits where ants are active.

When ghost ants are coming in from outdoors, control options include:

• Applying a residual insecticide on the outside perimeter of the building as a spot treatment, and crack and crevice treatments around doors, windows, holes, and other potential ant entry points.
• Tracking the ants to find and treat the nest(s).
• Placing liquid or gel sugar baits where ants are active. Baits should be in stations or otherwise protected so that they do not dry out. Replace baits regularly. Also bait at electrical boxes and where utility lines enter the building.

Supplement exterior service by caulking and sealing potential ant entry points, and by recommending that the client make the yard less attractive to ants by trimming trees and bushes away from the structure, eliminating debris and woodpiles along the foundation, keeping mulch six inches back from the foundations, and correcting moisture problems such as sprinklers spraying on walls.

The authors are well-known industry consultants and co-owners of Pinto & Associates.