It is not surprising that the ants are back this year. Products used for general ant suppression include various sprays, dusts or granules applied to lawns. These surface-applied treatments can temporarily reduce numbers of ants foraging through lawns and on garden beds. However, such treatments do not penetrate into colonies nor do they affect ants that use below-ground tunnels for much of their travel. Similarly, applications of such insecticides made directly to nests will often kill only surface foragers, again providing only temporary control. The great majority of the ants within the nest will not be affected unless insecticides thoroughly penetrate into the colony, which may extend a few feet deep. Where entrance areas are disturbed by insecticides or other activities, colonies will often abandon the treated area and establish new entrances at a different location.

Baits in refillable bait stations provide the safest effective treatment for do-it-yourself ant management outdoors. The ants feed on the bait and return it to the colony where it is shared with nest mates. The types of insecticides used for baiting ants are different than those used as sprays around building perimeters or in spot treatments. Instead of being fast acting, these have slower effects that allow the forager ant time to carry the treated food back to the nest. Boric acid, borax and arsenic trioxide are some of the older insecticides used as baits. Others act as insect growth regulators, affecting insect hormones that affect growth or prevent queens from producing fertile eggs. In recent years, several new insecticides have been marketed that have different activity allowing highly effective disruption of ant colony functions (e.g., fipronil, dinotefuran, indoxacarb). Food baits that are applied as gel droplets or are in bait stations that provide liquids have been marketed. Solid food-based baits are also available now in a broadcast form for use outside.

Several features determine if ants can be successfully controlled with baits. Perhaps most important is that the bait is acceptable to the ant so that they will feed on it. Feeding habits of the various ants found in homes vary with some preferring sweet materials (e.g., field ants, cornfield ants), others favoring greasy materials (e.g., pavement ants). Another important factor in bait acceptance is moisture content. Baits often become unattractive when they dry out, a common problem in the arid climate of Colorado. For this reason, liquid and gel formulated baits may often be more readily accepted by ants. Carpenter ants are one group of ants that will not visit most solid ant baits but will feed at some liquid or gel sugar-based baits.  

Alternatives to insecticides are sometimes sought. Boiling water can kill small colonies that do not extend too deeply. I personally have had good results by pouring boiling water on the mound or anthill. Look for colonies under mulch, gravel, stones, landscaping timbers, or pavement. Exercise caution in handling boiling water.  

 

Homemade ant baits are sometimes prepared. These involve incorporating a small percentage (ca 5-10% by weight) of boric acid or borax with some acceptable food. Since feeding preferences of ants vary, test several foods to see if they are visited. Among the commonly available foods accepted by ants are either sweet materials, such as honey or apple jelly, and/or greasy, protein rich materials, such as peanut butter. If these baits are made, they must be applied in a manner so that pets or children can not reach them. Placement of the bait in a sealed container with punched entry holes can produce a more protected bait station. Baits containing boric acid/borax also cannot be applied directly to soils where plants are growing as boron-containing materials can be soil sterilants.  

None of these methods of control will totally eliminate the ants, but will reduce their numbers to a more tolerable level. Overall, the activities of ants are quite beneficial. Many feed on other insects, including pest insects. Ant scavenging helps to recycle organic matter and their tunneling is useful in aerating and mixing soils. If they are not damaging plants or your landscape, they may be harmless. Ant populations rise and fall seasonally,so you will likely not have a large number of ants forever.  

Please see this link for an extensive discussion of ant control.
https://extension.colostate.edu/topic-areas/insects/ants-in-the-home-5-518/

Thank you for your inquiry.