Most ants occurring around structures have a preference for “eating out,” that is, food that is not produced within the nest. True, there are a few ants where this rule does not apply, such as leaf cutter ants that raise fungus gardens as a food source, but these ants are rarely a problem around structures in the United States. Generally ants prefer to find food quickly (fast food) outside the nest.
Ants may feed inside structures on food items in cupboards or on spilled food, especially early in the season. The most popular food item for many types of ants that leave the structure is a product of homopteran insects — honeydew produced by aphids and scale insects. These insects feed on trees, shrubs and many types of vegetation. Many ants also will feed on other insect prey and take whole food items back to the nest. These ants are hunters seeking insect prey feeding on vegetation. Others are scavengers on fruit or other possible food items.
Ants are opportunists at foraging and will feed on what is available. Carpenter ants and other ants have been found feeding on dead birds, dead bats and other materials. Ant diets vary throughout the year, but carbohydrates are always important as an energy source.
Early in the spring in most northern areas, an increased number of ants appear with the lengthening of the day and warmer temperatures. The ants need water and energy in the early season. Homeowners may note ants suddenly appearing in kitchens and bathrooms for water and around food items, especially foods with sugar such as honey, syrup, fruit or, occasionally, a sweet item such as pastries. Usually ants feed outside the structure, but early in the season ants will forage on food items inside. This is typical behavior for carpenter ants in the spring and may also apply to odorous house ants, velvety tree ants and others. Warmer temperatures occur within the structure and ants make their appearance inside before going outside in warmer weather to forage.
|Ants and aphids feed on trees, shrubs and many types of vegetation, including this fir tree.|
Vegetation in close proximity to structures, fences, wires or other structural guidelines provide ants with access to their “fast food” sources in the trees and other plants. These guidelines are comparable to freeways to ant foraging sites. Many different ants share features such as seasonal activity and foraging venues. Identification of the correct species and knowledge of the food habits and life history of that species will facilitate management.
Breaking the fast food habit is crucial to ant management and includes both identification of the ant species and the inspection that can be divided into several areas: the initial contact, the on-site inspection and the follow up.
Initial Contact. In a management strategy for ants, time is valuable and information gleaned from the initial contact will assist in reducing time spent on the site inspection. Initial questions will vary depending on the time of year of the contact. Good introductory questions include: “How many ants are you seeing daily or weekly?” and “How long have you been seeing ants?”
Answers to these questions give a hint as to the size of the colony and the length of time it has been there. A good suggestion is to request that the client collect some ants for you. As the appearance of ants is sporadic, ants may not be available on a home visit, particularly early in the season. Having the collected ants will allow you to make a positive identification — the first step in management.
|Carpenter ants and other ant species have been found feeding on dead birds.|
Other questions that provide information before the on-site inspection include: “In what rooms are you seeing the ants?” and “Have ants been observed on food items?” Positive responses to these questions indicate ants are overwintering in the structure and may have been established the previous season. Obviously a larger population is more challenging to control.
Another good question is: “Are winged ants present?” Knowing that carpenter ants produce winged reproductives in the late summer that overwinter and make their appearance in spring (late April to early June) helps identify this group of ants. Winged forms of carpenter ants will not swarm inside a structure unless a nest has overwintered within the structure. Odorous house ants and velvety tree ants seldom swarm inside structures, although winged forms may occur outside later in the year. Winged reproductives of moisture ants (Lasius spp.) appear in late summer (mid-August to mid-September). Thatching ant and pavement ant reproductives fly in July. This knowledge about life histories is important in identification and estimating the length of time the ants have infested the structure.
Knowledge about the history of the structure also may be useful. Questions such as: “How old is the structure?” and “How long have you lived here?” provide valuable information. In older structures, there is higher probability of moisture leaks, water damage, previous infestations, remodeling or construction changes. A homeowner who has recently purchased an older home may not have all this information.
Other critical questions that can be asked and later observed during the on-site inspection are: “How much vegetation is in contact with the structure?” and “Are large trees located near the structure? If so, what type are they?” Some homeowners are not aware of the importance of vegetation and may not have noticed recent growth. These extremely important features require special attention during on-site inspections. Large trees can serve double duty as sites of parent nests and fast food for a colony or partial colony infesting the structure.
On-Site Inspections. No amount of previous information can entirely replace the on-site inspection. With the Internet and other social media today, many homeowners have researched their ant infestations in detail. Some sites contain information regarding ants and their life history from other parts of the country. But knowledge of the ants and the life history of the ants in your specific area is important to developing your management strategy and in educating the homeowner.
|Homeowners may notice ants suddenly appearing around food items, especially foods with sugar such as honey, syrup, fruit or sweets such as pastries.|
For nearly all species of ants, vegetation becomes a critical feature. Trees, both evergreen and deciduous, shrubs and other plants that touch the roof, walls, porch, deck and wooden fences form ideal runways for ants to leave the structure and forage for aphids and insects. There should be no contact between vegetation and the structure. Trees and vegetation contribute added moisture to a structure that could lead to wood decay and other structural problems in addition to ant infestations. Ants forage from the structure into vegetation for insects and return to the structure. Perimeter sprays and baiting at the roof level are not regular management strategies, and ants can avoid baits and perimeter applications by utilizing routes through vegetation. Even though odorous house ants or pavement ants may stop to forage on spilled food inside, their food of choice is outside.
The routes to foraging sites are also facilitated by fences and gates located near or in contact with the structure, as well as wires and cables that lead away from the structure, particularly through trees. Ants will navigate these as freeways with easy access to food items in the trees. Two innovative solutions for finding ant trails into a structure include:
|Trees that touch homes form ideal runways for ants to enter and leave the structure to forage.|
Bait with freshly killed insects, other rich protein sources or vials with 25 percent sucrose to attract the ants.
Locate possible foraging sites near the structure such as trees or shrubs with aphids or other insect prey, watch for ant activity, then follow the foraging ants to nest sites either inside a structure or outside nesting sites. Observe the base (lower three feet) of a tree trunk for foragers that are climbing into or away from the tree.
Gather as much information on ant movement as possible from the inspection. Questions to the homeowner might include: “Have you observed ants outside the structure?” and “Where are the ants observed?” Children with outdoor activities can often provide valuable information regarding trailing and foraging ant activity. Include this source of information if possible.
Ants may have a parent nest or other nesting sites outside the structure. Examine any item in the yard such as children’s playthings, boards, planters, furniture or debris. Small ants such as odorous house ants, Argentine ants, moisture ants and velvety tree ants will form temporary nesting sites under various materials left undisturbed in the yard. For all ants, particularly carpenter ants, investigate stumps, driftwood, railroad ties, landscaping timbers and firewood that could serve as a parent nest. These sites will include areas high in moisture required for brood production.
Investigate hot tubs thoroughly for ant habitats. This ideal location provides water, temperature and nesting sites in the insulation around and under the hot tub. These are often placed in landscaped areas where “lunch” can be foraged.
Inspect the foundation or lower edge of the structural siding. An adequate space should be provided to prevent moisture damage to the lower edge or the siding. Include inspection for damage to doorframes, decks and porches. Determine entrances to the structure by examining these areas, particularly if there is moisture damage.
Management. Several baits are available for ant management. Gel baits with a carbohydrate source and toxicants are particularly effective. Finding and baiting ant foraging trails and entry points into the structure is particularly useful and will allow ants to contact, forage and transport the bait to the nest. Granular baits or liquid baits are also effective for ants. A good strategy is to try several baits at each location to determine the bait to which the ants are most receptive. Although baiting may be more time consuming because of subsequent evaluations, many homeowners are receptive or even demand baits because it appears to be more directed to the pest ants and more environmentally friendly.
|Other insects also can be food for ants, such as these dead cricket parts.|
Another strategy is to treat trails and perimeters of structures to eliminate the ants as they exit or enter the structure. Some of the perimeter spray will be transferred to nest mates, and the colony can be eliminated as toxicants are distributed from ant to ant. A combination of baits and perimeter sprays also can be made while keeping the two strategies separate, such as baiting on the interior and placing perimeter sprays on the exterior or applying other combinations where the two formulations are kept in separate domains.
Follow Up. Especially on problem sites, a follow-up evaluation will determine the efficacy of your management strategy, whether a bait or perimeter-spray application was used. Follow the fast food routine of ants. After two to four weeks, set out small vials of sugar (25 percent sucrose) solution or honey at key locations such as former trail sites and ant entrances into the structure. If present, ants will be attracted to these stations during the foraging season.
In summary, keep in mind the proper identification of the ant species, the biology of that species and the foraging activity of the species as it forages for its fast food. Recalling the foraging activity will assist in developing a management strategy for eliminating the pest ant.
The author is professor of entomology, Spokane Falls Community College, Spokane, Wash. To contact Dr. Hansen, write firstname.lastname@example.org.