I had heard before that cinnamon works great as a natural deterrent for ants so when I discovered two colonies of ants swarming outside my front door I had to give it a try. Then, like most scientific inquiry I found that I had a few more questions: How do ants signal? What does the cinnamon actually do to them? Can other spices work?
You’ll need to find some ants, mine were in the “wild” but it’s also relatively easy to order them online. You will also need powdered cinnamon, ginger, garlic, sugar and whatever other spice you want to try. A try of some kind is a good idea too.
In this video there really two tests, the first is the creation of a barrier. You don’t have to have warring colonies to do this one just a clear path ants are traveling along. The second is testing how various spices effect the exploration behavior in general.
- First you need to find some ants, or perhaps some ants have already found you.
- Next take a fresh container of cinnamon and sprinkle a 2-3 centimeter wide barrier across the path of the ants. Ants can find small gaps and will work to clear it if they still sense a way through. Likewise the ants may not be stopped if the cinnamon is too old.
- Observe the ants changing course. If they do not avoid the cinnamon attempt to identify the exact species to see if they happen to be resistant. I read one paper saying that Pharoh ants were immune.
- Follow up with other potential barrier chemicals, like cinnamon oil or mint oil.
Efficacy of spices
- Again, find yourself some ants.
- Select some spices. Probably not more than a few at a time. Good options are cinnamon, ginger, garlic, pepper, chilli pepper or mint oil but feel free to try whatever you like.
- Prepare the spice samples by doling out approximately 1 tsp of the spice and clearing an indentation in the middle. Place a half teaspoon of sugar (brown or white is fine) in the middle and moisten with an eye dropper.
- Place the spices near the ants as well as a plane sugar pile, also moistened, to act as a control for the rate at which ants return to a food source. It may also be a good idea to surround the control with something neutral like sand or dirt from nearby (I neglected to do this in the video).
- Wait. No really wait, even with active ants it will take a while for the ants to discover the food. I waited about 45 minutes before anything interesting happened.
- Once ants do encounter the samples count the number of ants arriving at each sample and record the time. This can be graphed later.
Here is the data from the various spices I tried. I did not record any quantitative data for the barrier experiment, merely the qualitative fact that the ants would not walk across the cinnamon willingly.
I originally thought that the cinnamon merely covered up the ants regular pheromone signaling behavior but when reading the scientific literature most studies measured mortality of the ants and would often isolate just one chemical from the cinnamon. Meaning that the reason ants avoided the cinnamon wasn’t merely that they could no longer sense their intended path but that literally they found the smell repellant. These chemicals were usually Cinnamaldehyde or Cinnamyl alcohol which act as toxins for the ants (They also happen to be somewhat toxic to some species of cockroach). I also found similar papers which would use cinnamon oil (presumably containing high levels of the mentioned chemicals) and also mint oil.
Is is reasonable to assert that these plants develop these spice-like-chemicals in response to the environmental pressure of being eaten by insects. Many pharmaceuticals derived from plants are also toxic to insects in small doses (caffeine for instance). Furthermore it can be hypothesized that tropical plants like the trees in the Cinnamomum family have a constant pressure from insects attempting to eat them that it increases their survival rate to expend energy on creating these spice chemicals. However temperate plants may have less potent defenses because there less during the winter months.
It also may be possible that the other spices I tested simply blocked the pheromones without themselves being toxic since the ants did appear to occasionally walk across them to get at the sugar samples. In any case what deterring effect there was, was not as strong as the cinnamon.
Results and Interpretation:
Well at least the two species tested, Tetramorium caespitum (pavement ant) and Formica ligniperda (carpenter ant) showed a distinct repellency toward powdered cinnamon. It can be generalized then that at least one of the volatile chemicals in the powdered cinnamon is partially lethal to the ants. This is borne out by the fact that zero ants ever crossed the cinnamon barrier around the sugar during the test period. Likewise there was at least some deterring effect from the ginger though if the ginger has a toxin for the ants it is likely less potent than the cinnamon. The garlic is likely less potent or possibly simply obstructs the depositing of the pheromone trail when ants returned to recruit more workers. In the half hour observation period the ants returned to the garlic approximately half as often (12 vs 31) than the the sugar with no barrier.
https://en.wikipedia.org/wiki/Pavement_ant <-ants on sidewalk
https://en.wikipedia.org/wiki/Carpenter_ant <-ants at my parents house
Effect of Cinnamon on ants:
http://www.ijsrp.org/research-paper-0714/ijsrp-p31106.pdf <-cinnamaldehyde demonstrated marked deterrence but ant species was not specified.
http://0-auraria.summon.serialssolutions.com.skyline.ucdenver.edu/#!/search?bookMark=ePnHCXMw42LgTQStzc4rAe_hSmECzxUa6pqZGpmyILE5YAMhoAPcTMwtORlKgQGj4JlXDMroyZkpiTkKwL60ArAdChrBzitRcEyG3KegkJ-mEJyfmaMAOr8Jco2CgnNmXh7odh4Fn9TENIWUVNBqeYXEdKBscQnQiBQFz1zwOeEpCm7AkkTBEWgcaDAa2MLiZtB2cw1x9tBFrnbiCyBHPcSDZ9rMzcwNjcCNK2PSVAMAfqNS4w <-Leaf debris containing cinnamon leaves was shown to act as both an insecticide and repellent when placed near by red imported fire ants, Solenopsis invicta
http://0-auraria.summon.serialssolutions.com.skyline.ucdenver.edu/#!/search?bookMark=ePnHCXMw42LgTQStzc4rAe_hSmECzxUa6pqZGpmyILE5YAMhoAPcTMwtORlKgQGj4JlXDMroyZkpiTkKwL60ArAdChrBzitRcEyG3KegkJ-mEJyfmaMAOr8Jco2CgnNmXh7odh4Fn9TENIWUVNBqeYXEdKBscQnQiBQFz1zwOeEpCm7AkkTBEWgcaDAa2MLiZtB2cw1x9tBFrnbiCyBHPcSDZ9rMzcwNjcCNK2PSVAMAfqNS4w <-cinnamon essential oil consisting of 75% cinnamaldehyde was demonstrated to induce mortality in red imported fire ants, Solenopsis invicta
http://0-dx.doi.org.skyline.ucdenver.edu/10.1093/jee/97.2.575 <-Mint oil was demonstrated to be an effective repellent when used on ant colonies of red imported fire ants, Solenopsis invicta this article was cited by all papers concerning cinnamon effectiveness.
http://0-dx.doi.org.skyline.ucdenver.edu/10.1016/S1532-0456%2801%2900255-1 <-Cinnamyl Alcohol was tested along with some other chemicals for insecticidal effective on three different insect species including Carpenter ants (Camponotus pennsylvanicus De Geer) while the paper’s focus is comparing relative effective between chemicals and species it is taken for granted that all chemicals including Cinnamyl Alcohol were effective toxins.
http://www.entm.purdue.edu/ants/pubs/8.pdf <-cinnamaldehyde showed no effect on Pharoh Ants