One of the most successful of all insects, ants can be a serious nuisance pest in homes, hospitals, restaurants and other buildings. Their ubiquitous nature and social structure makes them particularly difficult to control.
The European Ant Challenge
Of the 10,000-plus ant species known to exist, approximately 180 have been identified in Europe. The vast majority live outdoors where they perform a range of useful functions including aerating the soil, controlling insect pests and breaking down organic matter.
Only a handful of ant species typically cause pest problems by virtue of their attraction to human and pet foods with high sugar and protein contents. The most common of these sweet-feeding pest species generally nest outdoors and include:
- Black garden ants (Lasius niger)
- Yellow ants (Lasius flavus)
- Red lasius ants (Lasius emarginatus)
- Pavement ants (Tetramorium caepsitum).
Ants which tend to nest in close proximity to or within buildings, can also be problematic in some cases. These include:
- Carpenter ants (Campanotus sp.)
- Pharaoh ants (Monomorium pharaonis)
- Argentine ants (Linepithema humile)
When ants begin to infest homes and attack people in yards and parks, they fall into the category of a nuisance pest. Some species can also be a public health problem and can short circuit electrical components enough to cause fires.
Their social organization, diversity and adaptability in the urban environment have made ants a priority for pest management professionals and homeowners.
Biology and Behavior
Ants owe much of their success to their advanced social structure. Clear divisions of labor between workers – scouts, foragers, larvae feeders and sentries, as well as between workers, queens and drones (reproductive males) make for the most efficient colony establishment, development and survival.
Exclusively responsible for egg laying, queens are completely dependent on foraging workers that provide food to non-foraging workers, developing larvae and drones in the nest.
Following pheromones originally laid down by scouts, foragers hunt out new food sources within 90 meters or so of the nest. Foraging workers continuously carry food back to the colony based in the sites, depending on species. As well as consuming it themselves, they share the food with all the non-foraging adults and developing larvae in a process known as trophallaxis.
This results in the well travelled ant trails between nest sites and their various food sources that characterize most infestations. Trails that become more persistent and difficult to disrupt with increasing use.
Research has shown that while fewer individuals can feed on liquids than on gel or solid food sources at any time, foraging workers typically consume five times more of a liquid bait than they do of a gel.
Another likely natural consequence of their adaption to feed on honeydew, it has also been shown ants share baits consumed in a liquid form far more rapidly and efficiently within the colony. As a result, dramatically improved rates of control can be seen compared to an equivalent gel bait formulation.
The particular challenge presented by ants makes it important to tackle them with a behavior-led BASF Integrated Pest Management strategy based around five key essentials:
1. Inspect to establish the extent and location of the infestation.
2. Prescribe the best treatment strategy for the particular situation.
3. Communicate to set the right expectations and gain sufficient co-operation.
4. Treat using the most effective products in the best and safest ways.
5. Follow-up to assess results, and re-treat if necessary.
Tackling Ant Infestations
Effective control of social insects like ants can only be achieved through measures which eliminate both the queens and their broods. Exclusion of foraging workers from food sources or their elimination – either physically or by chemical treatment – is rarely, if ever, sufficient to give more than temporary respite from most infestations.
The only reliable way of ensuring complete control is to provide foraging workers with an attractive, powerful and readily-accessible insecticide bait which they both consume themselves and distribute throughout their colonies.
This approach harnesses natural trophallactic ant behavior to ensure all individuals, particularly queens and their larvae, receive a lethal dose of insecticide.
Without it a combination of the existing brood (eggs, larvae and pupae) and the prodigious egg-laying capacity of the queens can easily bring infestations back to their original level within a few weeks of treatment.
For the greatest effectiveness and reliability, the ant bait needs to be based on an insecticide which is:
- Undetectable to all ants yet powerful enough to be lethal when ingested or physically transferred within the colony in minimal amounts
- Sufficiently delayed in its action to allow foraging workers to distribute it widely to all adults and larvae within the colony before succumbing
The bait formulation must further be:
- Highly attractive and appealing to ants to stimulate the greatest possible worker feeding
- In liquid form to ensure the most rapid and effective active ingredient uptake and redistribution throughout the colony
Good baiting practice is equally critical to success. In particular:
- Indoor areas should be cleaned and alternative food sources removed before treatment
- Baits should be placed where they will not be rapidly removed by cleaning, and preferably close to known or suspected ant access points and foraging trails
- Areas previously treated with repellent insecticides should be avoided
- Outside baiting should focus on active ant foraging trails, with bait points placed as close to nest sites as possible
- Bait should be placed on non-porous surfaces and protected from rain, ideally in specialist bait stations
Ant baiting will typically take between 10-14 days to give colony control. So where rapid elimination of foraging individuals is important in sensitive locations, it may need to be complemented with tactical spraying of a fast-acting insecticide. As well as rapidly eliminating visible indoor foraging ants, an insecticide with a repellent nature can act as a useful perimeter barrier to further ant entry. It is important to note though that repellant insecticides should not be used close to bait treatments as their repellant nature may prevent ants coming into contact with the bait.
- Be targeted at indoor ant trails and wall/floor junctions in the vicinity of food sources
- Include typical entry sites around windows and doors, drains and pipe runs
- Avoid external ant trails in the vicinity of baiting points
It is important to appreciate that ants are extraordinarily persistent in following trails to food and small enough to gain entry through even the tiniest of openings. This makes thorough perimeter treatment with repellent insecticides vital to ensure effective exclusion as well as immediate elimination of obvious signs of infestation while baiting achieves its full colony control effect. Where infestations are large, well- established or otherwise particularly challenging, external spraying of nests and ant trails with a slower acting, non repellent insecticide will be valuable.
Although generally ineffective on their own, physical means of excluding ants from buildings or food sources can be valuable alongside chemical controls. This is especially noticeable in guarding against re-infestation from new colonies around sensitive locations.
The most effective measures include:
- Ant-proof storage of foods in truly sealable containers
- Regular cleaning of floors and surfaces to remove spillages and scent trails
- Proper disposal of kitchen scraps and food waste
- Permanent sealing of access points with flexible caulk
Based on a combination of internal, external and perimeter treatments, the most effective ant treatment programs include:
- Thoroughly inspecting the premises in dry weather to identify the level of infestation, species of ant (where possible), main trails and access points
- Tracing external ant trails as far back to the nest as feasible, bearing in mind that trails may be very difficult to locate when conditions are wet
- Placing sufficient Fourmidor® ant bait along external ant runs, using bait stations or other weather protections
- Placing additional Fourmidor® bait points at perimeter access points and along internal ant trails in locations least likely to be cleaned away wherever immediate visible pest elimination is not the overriding priority
- Thoroughly spraying Fendona® SC along indoor trails and perimeter access points to complement external Fourmidor® baiting in sensitive locations requiring immediate visible pest elimination
- Fully informing customers of the program and the location of indoor baiting points, in particular warning them not to clean them away or use aerosol insecticides near them
- Returning 2-4 weeks after treatment to check for any continuing signs of infestation, replenishing bait points if they are empty and ants are still visible
- Advising customers on effective physical controls to minimize the danger of re-infestation