Utilizing Pheromones to Discourage The Notorious Household Ant.
Do pheromones hold the miracle answer to controlling Argentine Ants, one the most aggressive pests on the planet?
The Argentine ant is one of the most common household pests known to humanity, often invading in search of food or water. The main problem is that large numbers of Argentine ants will be attracted to a detectable food supply or water source, resulting in a simultaneous attack by hundreds of insects. What can a homeowner or apartment dweller do when besieged by an onslaught of these determined invaders?
As such, numerous studies have been carried out over the years to try to ascertain different ways of controlling them. More than 30 years ago, research showed that (Z)-9-hexadecenal (Z-9) strongly attracted Argentine ant workers and that it is present in whole body extracts (Cavill et al. 1979). It was thought that this was the Argentine ant's trail pheromone and its method of attracting large numbers of worker ants to any one site. Argentine ants even follow artificial trails of Z-9, further adding to the hypothesis that this is its trail pheromone marker of choice (Choe et al. 2012).
Using Basic Ant Deterrent Management.
It has, therefore, always seemed an obvious choice to use Z-9 as a component of ant management. Added to that, Z-9 has demonstrated low toxicity levels and is readily available commercially, so it makes sense in many ways. A few methods have been trialled, including:
• Adding Z-9 to sugar baits. This increased bait consumption by 33% (Greenberg and Klotz 2000)
• Using Z-9 as a trail disruptant. The theory is that saturating an area with false trails could easily confuse ants, sending them on wild goose chases away from your home. (Suckling et al. 2011)
• Using an encapsulated spray formulation of Z-9 resulted in fewer visible foraging trails and fewer ants foraging at tuna baits for at least two weeks (Suckling et al. 2010).
The trail disruptant theory was tested over the course of two years. Z-9 dispensers were placed in small garden plots and, although the study did show that foraging trails were disrupted, it also concluded that Argentine ant populations were not reduced (Nishisue et al. 2010).
In another study, Z-9 dispensers were used in combination with baits. The results showed trail disruption as well as lower ant populations compared to using either baits or Z-9 alone (Sunamura et al. 2011).
Whose on the Wrong Path, Us or the Ants?
An insightful study by Choe et al. in 2012 highlighted that Z-9 cannot be found in measurable amounts in ant trails. This means that despite z-9 acting like a trail pheromone, it actually isn't. It may be that the Argentine ant uses Z-9 at food sources and at the nest as a method of gathering foragers to the site.
If Z-9 isn't quite the key to ant control that had been anticipated, what are the alternatives? In arid areas, water baits can help to disrupt foraging ant trails. Strategically placed water sources can lead ants out of structures, forcing them to create new trails instead (Enzmann et al. 2012). Liquid boric acid baits can also be used in a similar method. The ants are highly attracted to these sources and are then killed by the baits (Klotz et al. 1998).
Peppermint, spearmint, wintergreen, cinnamon and clove 1% essential oils are effective at repelling ants for one week, (Scocco et al. 2012) with spearmint being the most effective. This is also a natural method, which may be favoured by many consumers.
In short, Z-9 is not the miracle cure to fighting Argentine ants that had been originally hoped. However, the good news is that Argentine ant management can be addressed through the strategic use of trail disruptants and repellents.
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