We pest management professionals (PMPs) are blessed to have such a fantastic assortment of insecticide baits to choose from especially for the control of ants. In most cases, it is possible to find at least one brand of bait that will be accepted by foraging workers of just about any structurally invasive ant species. When accepted baits are incorporated into our customized ant integrated pest management (IPM) protocols, we generally achieve the expected results in a reasonable period of time.
However, there are some classic situations that will dash our expectations of a quick-and-easy fix to our customers’ ant problems. Diligently tackling such challenges serves to keep us PMPs on our toes and, in the process, makes us heroes to our customers. Let’s look at two thought-provoking situations that address the use of baits to enhance ant management.
Are ants losing interest in your baits?
Odorous house ants (OHA) often form numerous colonies, both in the landscape and in the sandwiched construction elements of outside walls, sill plates and roofing. Some PMPs have a wonderful obsession about searching out as many individual colony sites in and around the structure as possible, and taking them out point blank with a quick knock-down insecticide. As you can imagine, this ideal approach takes time, which is a precious commodity not often afforded technicians who usually run tightly scheduled routes.
Therefore, in most cases, the technician will apply an exterior perimeter treatment with a residual liquid insecticide, as well as perform a crack and crevice treatment indoors using a non-repellent residual liquid or dust insecticide. This is a shotgun approach, which may or may not achieve temporary or seasonal control of OHA in and around the structure.
Technicians who are equipped with an assortment of insecticide baits will continue the initial treatment by strategically placing ant baits both outdoors and indoors. Certainly baits can increase a PMP’s chances of controlling invasive antsif the ants accept the bait and stay interested in the bait!
How can a technician tell if foraging worker ants will accept a particular brand of bait? By performing a “taste test” on foraging workers, of course! Yes, this takes time.
And how can a technician know that the problematic ants are continuing to accept the baits? By scheduling a follow-up visit at that account, within a week of the initial treatment, to observe the bait placements and the ants’ responses to them. Yes, this also takes time but not as much time as working numerous callbacks into the weeks and months to come!
A follow-up visit to an account will give the technician an opportunity to do two things:
1. Switch bait formulations, if necessary, to accommodate the colonies’ preferences.
2. Add more bait and placement sites to accommodate multiple colonies’ supply and demand requirements, as well as changes in foraging behavior.
Furthermore, when foraging ants mysteriously “figure out” that particular baits are deadly to the colony and reject them, a technician on a follow-up visit will notice and can take the appropriate steps.
Baits (and ants) can be tricky
Recently, while field-testing a promising new gel bait formulation, I was surprised by what I observed. In one instance, I watched black carpenter ant (Camponotus pennsylvanicus) workers immediately establish foraging trails to the bait placements. These carpenter ants appeared to be consuming the bait; however, upon closer examination, it became apparent over time that the workers’ gasters were not swelling and the volume of the bait was not diminishing.
Something about that gel bait formulation seemingly made it difficult to consume. Eventually, the workers from this particular colony abandoned the foraging effort at the gel bait placements.
A technician performing a quick taste test of this gel bait at an account would notice the initial acceptance of the bait and then head on down the road to the next stop, unsuspecting of the impending bait abandonment. When I performed an acceptance test of this same gel bait formula with a colony of the nearctic carpenter ant (C. nearcticus), workers rejected the placements immediately. Interestingly, another entomologist field-testing this bait formulation in another state reported continued acceptance and successful ingestion of the gel by colonies of two other carpenter ant species, C. modoc and C. vicinus. So, the take-home message here is that, when it comes to gel baits (and likely other bait formulations), not all carpenter ants respond the same.
And when it comes to insecticide baits and ant control, I have come to the conclusion that the only way I can have confidence in the treatments I perform is to hang around and watch what the ants do when they encounter the baits not just the immediate response of the foragers, but the behavior of the workers after several minutes of feeding (or attempted feeding). We PMPs can spend a little extra time at our accounts initially, or we can spend a lot more time at what have become problem accounts later on.
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