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Features - Ants

Practical Tips for Trailing Ants Indoors


Editor’s Note: This article was adapted from Techletter, a biweekly publication from Pinto & Associates, Mechanicsville, Md. To subscribe, visit www.techletter.com, or call 301/884-3020.


To control ants indoors, whether with crack and crevice treatment or baiting, you first need to

Start by talking to your customer. Where have ants been seen? When? How often? Are there any areas of the home that have had moisture problems or leaks? If calling on a residential account, ask any children in the home. They notice things (like ants) that adults may overlook. In fact, a child may take you right to the nest.

Work with a floor plan or sketch of the building. Mark areas where ants are actively trailing. This is especially useful to pinpoint active sites for a baiting program. Sometimes random trails that make no sense at first will direct you to a common nest site once you see them mapped out on paper.

If your customer hasn’t provided any leads, start your search by checking areas where ants are attracted to moisture – bathrooms, kitchens, laundry rooms, boiler rooms, etc. Follow edges along baseboards, around tubs, at the base of toilets, and along pipes and appliance cords. Like cockroaches, ants tend to trail along man-made edges such as countertop backsplashes and floor baseboards.

Other inspection tips that have proven successful include:

• In kitchens, look for ant trails along edges and corners of baseboards, countertops, stove and cabinets. Check along pipes under the sink. Look inside cabinets, especially the back edges of cabinets containing food packages.

• In uncarpeted areas, slide a knife or a piece of paper along the gap between the bottom edge of the baseboard and the floor. This will bring out trailing ants that can’t be seen. Use this same technique when checking for ants under door threshold plates.

• In carpeted areas, ants like to trail under the edge of the carpet next to the baseboard (see related story on page 90).

• Look for small piles of soil on the floor where ants have pushed it out of wall voids up through a crack in the slab, or out from under door thresholds or patio door expansion joints.

• Other places to check for evidence of ants indoors include window sills, inside switch plates, along electrical lines and pipes running inside voids, bath traps and subslab heat ducts.


Remember that some ants (carpenter ants, for example) are most active at night. You may not find foraging workers during the day. Placing spots of non-toxic food baits like jelly can help locate areas where ants are actively foraging.

If you find an indoor ant trail that seems to end abruptly, look closely for a point where the ants enter a wall void, disappear through a crack in the slab or exit under a door. The ants could be nesting inside that wall void, inside a hollow door or in a window frame. But it’s also very likely they’re simply foraging inside from an outdoor nest. Check outside directly opposite the point where the trail disappears to see if you can pick up the trail continuing to an outside nest.

find the ants. If you find the nest, you can treat it directly. But in many cases, you’ll have to locate ant trails and aim your controls at the foraging ants.


Inspecting Under Carpets: You’ll Be Surprised by What You Find

Many indoor-nesting ants like to trail along walls just under the edges of carpeting. If you find ants in a carpeted room, use a pair of needle-nose pliers to carefully pull up the edge of the carpet. Start with a carpet edge that is along an exterior wall, especially in front of a patio door or fireplace. Pull up a portion of the edge of the carpet, just enough to look underneath. Don’t pull up a large section because you may have trouble re-attaching it to the tack strip beneath.

If you find ants under the carpet, follow their trail as far as you can. They may lead you to their nest in a wall void or to the point where they are entering from outside. Sometimes ants will move soil up into the walls of a structure. If you find piles of soil under the carpet, it means you’re close to a wall void nest or entry point through an expansion joint or a crack in the slab. Push the carpet edge back onto the tack strip after inspection.

(Adapted from the PCT Field Guide for the Management of Structure-Infesting Ants by Stoy Hedges)


Baiting Doesn’t Need to Be Difficult

There are basically three steps to follow when beginning an ant baiting program:

Know the Ant. Identifying the ant will give you some clues as to the type of bait the ant prefers (sweet baits or protein baits). This information will help you locate what they’re feeding on in the account and will give you clues as to where they are nesting and when they are foraging.

Find the Trails. You need to locate ant trails and feeding sites so you know where to place the toxic baits. One way to do this is to pre-bait first with non-toxic bait. Pre-baiting (or survey baiting) helps determine where the ants are feeding and which type of food bait they are feeding on.

Choose the Bait. Ants can be very finicky. Some prefer sugar-based baits like honeydew; other ants prefer oils and grease and will eat only protein baits. Sometimes the same ant species will switch from one type of bait to another when conditions or seasons change. Bottom line: have a number of different baits in your control arsenal and keep alert to changes in ants’ feeding preferences. If they’re not feeding on what you put out, change bait or offer several different kinds of bait.

Here are some additional suggestions for improving your ant baiting programs:

Place baits directly on trails, along edges and near water sources (i.e., sinks, toilets, potted plants, etc.) and heat sources like appliances.

Make sure you place enough bait. If ants remove all the bait before your next service, they may not have taken enough bait to kill the colony and then may move to a new feeding site.

At first, place small amounts of bait in lots of sites, then concentrate on the most active feeding areas and discontinue baiting sites with no activity.

See that the baiting sites are kept clean. You don’t want other food crumbs, spills or pet food to compete with your bait applications.

Don’t apply gel bait to surfaces that have been recently sprayed with insecticide, or to food-preparation surfaces, or surfaces that get hot, or to porous surfaces or fabrics, or inside electrical equipment.

When using granular bait outside, it’s best to bait on a warm day, 70 to 90 degrees Fahrenheit. Don’t bait before or after a heavy rain, and don’t irrigate immediately following treatment (unless the label instructs you to do so).

If you’re using granular baits for small ants, make sure the granules are small enough for ants to pick up and carry back to the colony.

Remember that toxic bait is food-based and spoiled bait can actually repel ants. Some baits without preservatives will need to be replaced weekly. – Larry Pinto and Sandra Kraft