Hold Your Breath (AKA: What doesn't kill you...)
I remember my first entomology class in college. I was super excited because we had to do an insect collection. This meant I got to be outside, hiking, in nature where I was particularly happy. Collecting insects was just a bonus. One of the other students asked about collecting, particularly, could we asphyxiate the insects we collected instead of using the killing jar (basically gassing them). This brings up the important point of how resilient and adaptable some of our pest species are: they can void adverse conditions including what we (pest management professionals) throw at them.
I saw this article today and it was really what prompted this blog post. I’ve mentioned many times how major weather events can cause pest issues. They are avoiding conditions that are unsuitable to their survival and moving to areas that are more conducive to continued existence. Australia has been suffering from extreme rains and flooding recently and these spiders are trying to get to dry land.
Bonus – fire ants do this too, but they do it in a “raft” where they link together and constantly spin the raft so none drown as they work their way to higher ground.
I work with many food companies and at some point, the question of cold treatments will always come up. The simple answer is yes, as long as it’s cold enough and long enough. Warehouse beetles are particularly cold toleratant and to kill the larvae (the most cold-tolerant stage) it took 64 hours at 0F (-18C). That’s with just the beetle in the freezer, it takes much longer when that beetle is inside a box of cereal on a pallet wrapped with plastic or 50lb. bags of flour stacked up. Getting that center mass down to a killing temperature could take weeks depending on the product and how dense it is.
Bonus – it’s not just our inside pests: there is a species of African midge that, as a larva, was found to survive liquid helium (-270°C/-454oF) for up to 5 min. with a 100% survival rate.
Drowning and cold don’t work, how about starvation? I was researching ants recently and came across acorn ants. They are so named because their colonies are small and often found inside acorns. Seriously, an entire colony of ants in something as small as an acorn! You can imagine a small colony of tiny ants doesn't need that much food, but they still need some to raise the brood and keep the workers going. A paper looked at controlling colonies and kept a lab colony that lasted more than eight months with absolutely no food (but they did provide water).
Bonus – ants aren’t your thing? Bed bugs (adults) can survive up to 143 days without feeding.
That brings us to the initial question from my Entomology 101 class: can we asphyxiate insects? We can, but like cold and starvation, it takes a while. I work with several museums that have very sensitive pieces of art. If insects get to these pieces (think wooden frames, furs, feathers, etc.) it can be disastrous. So using what is basically an "oxygen absorber", you can reduce the amount of usable air in a space. The trick is getting the oxygen content below 2%. Depending on the size of the space being “treated”, the temperature, and the insect species this could take weeks.
Bonus – stored product pests like weevils are tolerant to asphyxiation: it takes over 45 days to get to 99% mortality with carbon dioxide (displacing oxygen) treatments.
With all these adaptations of avoidance and tolerance to adverse conditions, it may seem hopeless to control insect pests. It isn’t. Because it isn’t about using just one method, it’s about using all the tools, knowledge, experience, and science we have to keep pests out of structures, foods, and protect people’s health. My first entomology class taught me it wouldn’t work. My second entomology class taught me what else to do to make it work. All the years since then have been accumulating the experience and knowledge to help companies make it work faster and more effectively.
Have you had any experience with any of these methods for special treatments? Comment below! If you are ready to see if your pest management plan is up to date and effective, contact us here!
Lagniappe - Even eating insects isn't enough to prevent their potential harm: sometimes the bugs bite back!