Jeffrey Einam from Bayer’s Crop Science Division explains why understanding ant behaviour is the key to successful ant control.
With the change of seasons upon us and the warmer weather on its way, service calls to deal with ant problems will be on the increase. Therefore now is the perfect time to reacquaint ourselves with the enemy and prepare to go to battle. By gaining a better understanding of the fascinating behaviour of ants, it can significantly increase your success with ant baiting.
As social insects, ants are committed to the survival of the colony and all their daily activity centres around their needs at that given moment. In their native habitats, they work hard to find the available resources around them to meet the needs of the colony and are often at the mercy of the weather conditions that exist. In the urban environment however, opportunities present themselves almost on a daily basis for them to exploit and ‘supercharge’ their colony life cycles.
Ant species that were once suppressed in their native habitat suddenly become a pest problem to us and yet we are often enabling this behaviour by the way we collect, store, prepare and dispose of foodstuffs. Even our choice to plant gardens with flowering plants and watering on a frequent basis provide them with significant opportunities and predictability not found in unmodified habitats.
Addressing these situations is often some of the most effective non-chemical strategies we can deploy by reducing or removing the attraction in the first instance. In many cases, our relationship with ants can go unnoticed if they don’t interfere with our lifestyle. However, once ants enter our personal space and we encounter them via bites and stings, active trails inside and outside structures such as homes, food storage contamination in commercial accounts or even damage to the buildings or structures around us, means they suddenly become incompatible and reach pest status.
This tolerance varies as we know, with some customers not considering them an issue whilst others see ants as one of their key indicator species for pest servicing. And for those in the second group, what is not good news for them is that ants are more often than not, considered one of the more difficult problems to address, particularly if the colonies are well established and/or supported by complex nest structures outside the jurisdiction of the site.
As pest professionals, we know and understand that ants do seem to have food preferences, whether they be proteins, fats and oils or sugars. And for many of us, this knowledge is often used with other visible physical features to identify what species we are encountering on site. For example, a fats and oil bait placed outside and fed on by ants could indicate the presence of a number of species, but when coupled with the knowledge that the ants are active outside and have major and minor castes that are red/brown in colour, we would conclude that we are dealing with a coastal brown ant (Pheidole megacephala) problem.
However, we have all seen ant species that we can positively identify that are not feeding on their ‘usual’ primary food source. This situation often occurs when the colony is seeking a particular nutrient for its current needs or seeking a balance in its nutrition. For example, at times during its life cycle, a queen requires protein and nitrogen for the purpose of laying eggs, so even if a sugar feeder, she may show a strong preference at that time for a protein placement.
A quote from Adam Kay in a paper he wrote in Behavioural Ecology sums it up quite well: “Preference reflects the relative value of items that are presented as alternatives.”1
In particular, it also helps us understand the decisions that are being made by ants when they face food choices. For example, if an ant colony has been feeding on food based on fats and oils which is in abundance, and a small dead insect is placed near their trail, they may appear to favour the insect offering, particularly when there are no other proteins available in the foraging area. Suddenly, a small but rare resource is chosen over a large available one.
This change in feeding behaviour is regulated by pheromones laid down by workers and topped up by subsequent (verification) visits by others. The stronger the pheromone trail the more recruitment occurs, until the desired feeding rate is reached. Pheromones are rather short lived and break down, so constant regular releases are required to maintain feeding.
When a change in feeding preference is imminent, pheromone trails would be laid by ants returning to the nest from the food source (insect in this example) and present a clearer signal to subsequent ant workers. A further regulation occurs as the current food resource is depleted. When the volume of resource exceeds the volume of an ant’s crop, they continue to release pheromones indicating there is still work to be done, but as it runs out, worker ants stop so that energy is not wasted by other workers returning to the site for no reason.
How does this behaviour relate to ant baiting and can we use this information to help us be more successful? Maxforce Quantum contains a complex sugar base inside a viscous liquid matrix. For species seeking sugars, it provides a high value resource that when feeding begins, can remain attractive for long periods of time. Additionally, being a liquid bait, it most likely has added attraction, as worker ants can ingest the liquid, as opposed to carrying solid particles from granule baits.
Volker Gutsmann, our global ant researcher based in Monheim, Germany, believes that liquid baits provide additional attraction to ants that can overcome an ant’s primary food preference. “We know that Monomorium spp. for example, won’t touch sugars in general, but they do if it’s a liquid. Ants being liquid feeders can’t resist a good feed if presented with a good one like Maxforce Quantum.”
The message here is don’t assume a bait matrix will only attract certain species because of their ‘usual‘ primary food preferences. It’s what they do on the day that counts, and why we have so many reported and confirmed feeding successes with Maxforce Quantum on many species not considered to be textbook sugar feeders. There is no doubt that a liquid matrix that contains a high level of moisture is attractive at times to colonies seeking water, but one that naturally protects from moisture loss and drying out can be a robust option for challenging sites.
How much bait should you place?
Once you recruit trailing ants to placements, allow yourself 5-10 minutes and come back to understand how many ants are trying to access the bait. Remember the behavioural trait of ants switching off pheromones when resources deplete. The last thing you want is put out too little bait, so the tip here is to adjust the number and size of placements to suit the activity you are attracting to ensure maximum uptake and impact of the baiting component of the program. Such a simple and easy action can really improve your success rate.
Jeffrey Einam, Market Development Manager ANZ, Environmental Science, Crop Science Division of Bayer
1 Kay, A. 2004. The relative availabilities of complementary resources affect the feeding preferences of ant colonies. Behavioral Ecology, 15(1): 63-70.