[Annual Ant Control Issue] Basic Baiting for Indoor Ants

Features - Cover Feature: Ant Control Issue

Tips and tricks about using ant baits.


Editor’s note: This article was reprinted with permission from Techletter, a biweekly training letter for professional pest control technicians from Pinto & Associates.

An effective ant bait should not be repellent to ants. Many ants are sensitive to pesticides and will quickly break up and move their colonies if there is anything repellent in the vicinity. The ant bait should be attractive only to the target ant (or closely related ants). An effective ant bait should have delayed toxicity. In other words, it’s important that the ants have time to feed on the bait, recruit other ants to the food source and carry the bait back to the colony before they die from the baits’ effects. Delayed toxicity can sometimes be frustrating for the technician and the customer who like to see immediate results. It’s important that the customer understands that the best and most permanent control will come slowly.

An ant bait is made up of an active ingredient (toxicant or pesticide) mixed with a food ingredient. Ant baits are available in several different formulations with different packaging. There are gel baits applied by tube or with a “gun” applicator, containerized bait stations, granular baits and liquid baits.

Sometimes indoor ants are not feeding inside at all but are instead foraging for water. A liquid bait should work well in this case. If you’re using granular baits for small ants, make sure the granules are small enough that the ants can pick them up to carry them back to the colony. If you use gel baits, don’t apply them inside electrical equipment or to surfaces that can get hot. Don’t apply gel baits to fabrics, porous surfaces, surfaces that have been recently sprayed with insecticides or surfaces where food is prepared.

Many ant baits contain insect growth regulators (IGRs) as the active ingredient. IGRs affect the development of immature ants by killing them directly, or by affecting egg production by the queen or by preventing the development of worker ants. Since IGRs do not kill adult worker ants, the baits are spread through the colony to affect development of immature ants instead.


How to Find Trailing Ants Indoors

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

Start by talking to your customer. Where has she seen ants? When? How often? Are there any areas that have had moisture problems or leaks? Also, ask the client’s children. They notice things (like ants) that adults may overlook. 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 and boiler rooms. Follow edges along baseboards, around tubs, and 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.

  • In kitchens, look for ant trails along edges and corners of baseboards, countertops, stoves and cabinets. Check along pipes under the sink. Check 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 to check for ants under door threshold plates.
  • In carpeted areas, ants like to trail just under the edge of the carpet next to the baseboard. Start with carpeting along exterior walls, especially in front of patio doors and fireplaces. Use a pair of needle nose pliers to carefully pull up just the edge of the carpet. Push the carpet edge back onto the tack strip after inspecting.
  • Look for small piles of soil on the floors where ants have pushed it out of wall voids or 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: window sills, inside switch plates, along electrical lines and pipes running inside voids, bath traps and sub-slab heat ducts.

Remember that some ants (Pharaoh ants, for example) are most active at night. You may not find foraging workers during the day. Placing spots of nontoxic 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, or disappear through a crack in the slab or exit under a door. The ants could be nesting inside in that wall void, or inside a hollow door, or in a window frame. But it’s also likely that 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. — Sandra Kraft & Larry Pinto


Probably the toughest problem in baiting ants is getting the carbohydrate/protein food preference right. Some ants prefer sweets, others prefer proteins and fats, and many ants will switch from one food to the other with little warning. The food preference switch is often seasonal and requires experimenting on the part of the applicator. When ants begin rejecting your bait, it’s time to try a different food type. Prebaiting with different nontoxic food baits before you begin the actual toxic baiting program can save effort (and products) in the long run.


Prebaiting (also called survey baiting) not only gives you an idea of what the ants are feeding on, it also helps pinpoint sites of the greatest feeding activity which tells you where to place your toxic baits. Prebaiting also can help you track ants back to their nest site. To prebait, place nontoxic food baits on strips of masking tape or in ¾-inch sections of plastic straws. Try several different foods to see which one is preferred. Two good test prebaits are mint apple jelly (sweet) and peanut butter (protein). Once you’ve discovered what the ants are feeding on in the account, eliminate those food sources so that you will get good acceptance of your toxic bait.

The Baiting Program.

Hopefully, as a result of your prebaiting, you now have an idea of the food that the ants prefer and you have located some prime feeding sites, ant trails and maybe even points of entry.

Place your toxic baits directly on trails when possible since some ants will not wander off of their trails. Place baits along edges where ants trail such as counter edges, door moldings, wall/floor joints, window frames and along baseboards. Also place baits near water sources such as sinks, toilets and potted plants. Bait near heat sources like light fixtures, electrical boxes, heat ducts, hot water heaters and appliances.

Place small amounts of bait in lots of sites. Leave enough bait to last until your next service visit. Remember that toxic bait is food-based and spoiled bait actually can repel ants. Some baits without preservatives will need to be replaced weekly. Once you’ve discovered the most active feeding sites, concentrate your bait placements in these areas. Discontinue baiting sites that have had no activity.

Many indoor ant problems originate outdoors. So look for nest sites outside and bait these areas too. Some technicians routinely place bait around the perimeter of structures to draw ants away before they can enter the building. Some baits, though, do not have a long active life when exposed to light and other outdoor conditions.


Woodstream Adds TERRO Products to Pest Control Solutions for PCO Market

Woodstream Corp. has added TERRO PCO Liquid Ant Killer to its product offering for pest management professionals, and will be available May 2015. The sweet, borax-based Liquid Ant Killer is formulated to quickly attract and kill common household ants, the manufacturer says.

TERRO PCO Liquid Ant Killer is designed for control of sweet-eating ants, including Argentine, ghost, little black, acrobat, pavement, odorous house, crazy and cornfield ants. Worker ants feed on the sweet, borax-based ant bait, then carry it back to the nest and deliver a dose to the rest of the colony. For interior and exterior use, the easy-to-use ant bait contains no unpleasant odor, the manufacturer says.

TERRO PCO Liquid Ant Killer is available in three sizes:

  • 1-gallon container – 4 per case
  • 16-ounce container – 12 per case
  • Pre-filled ant bait stations – 30 bait stations per carton/10 cartons per case/300 bait stations per case

According to Woodstream, key features and benefits include:

  • Attracts ants quickly
  • Slow-kill gives worker ants time to share bait with the colony and queen
  • Contains borax
  • No unpleasant odors
  • Use indoors and outdoors

For more information, contact your Woodstream professional pest control products distributor or visit www.woodstreampro.com.


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