Ants looking for food and water find both in your dishwasher. Carpenter ants, black and a half-inch long, and Argentine ants, a tiny 1/16 of an inch and light or dark brown, are the two species most likely to make an appearance within the dishwasher itself or its cabinet walls, as well as the floor underneath the dishwasher or the wall behind the appliance. Your strategy to solve the problem needs to focus on drying out damp spots, destroying ant nest elsewhere and closing access points.
Checking for Dampness
Before you begin tracing the ant trails, rectify any sources of leaks in the dishwasher. You likely have to remove the access panel at the bottom of the front to look for leaks from the pump. A leak around the door may mean it's time for a new gasket. Water may gather underneath the unit if it is out of level.
Check nearby sinks for leaks, too, especially at the water supplies and their valves.
Finding the Nests
Place honey, jam or even small pieces of lunch meat on wax paper in areas where you spot the ants. Both carpenter and Argentine ants prefer sweet foods but will occasionally go for fat or greasy baits. It may be easiest to spot them at night, when they are most active. Given the difficulty typically of accessing the area behind the dishwasher, pull out the stove if it is adjacent and open adjacent cabinets to track the ants.
Follow the ants to where they disappear behind the wall. If the dishwasher is on an exterior wall, head outside to see if you can follow their path to a rotted windowsill, tree stump or similar spot of opportunity for an outdoor nest.
Controlling the Infestation
- Boric acid. You can control nests in walls by puffing boric acid into any wall penetrations, such as around pipe collars or electrical outlets, and then caulking them shut. Follow up by puffing a light dusting against your baseboards, brushing any overspray firmly against the baseboard's joint with the floorboard or tiles to avoid risk to pets.
- Fresh sugary baits. Look for baits containing hydramethylnon, boric acid, sulfluramid or avermectin, and give them a week or more to work.
- Insecticides. To eliminate nests in rotting wood or stumps, the University of North Carolina Extension recommends granular ant baits containing fipronil.