A couple years ago I posted some thoughts on dealing with invasive ants in the garden and provided a recipe for homemade liquid ant poison (see The Uncarved Block - Ants!). My DIY ant poison has been successful, but, I have found liquid poison to be somewhat inconvenient – it is clumsy to distribute and goes bad quickly. Thinking back to my youth, I recalled how accidentally dropping a piece of candy would attract ants like crazy. So, I decided to try and make ant poison “gumdrops.” I have been experimenting with various formulations. This posting is a work in progress. I am having good results, but I’m still fine-tuning the proportions. Friends of mine have asked me for the recipe, so I decided to post it here. If you find it valuable, I would love to hear feedback which could help with improving these “gumdrops”.
I started with a recipe that I found online for gumdrops intended for human enjoyment. I removed all the niceties of a gumdrop that people might like to eat - flavorings, colorings, and attractive shapes. I also skipped any steps required to produce a pleasant texture in the mouth. All I cared about was creating a glob of stuff that is convenient to distribute, that ants will want to eat, and which contains a substance that will subsequently kill them.
The first batch I made was very soft and melted in the sun. In fact, while working in the garden, my original tray of “gumdrops” all melted together into a pool of liquid. They re-solidified when I brought them back inside, but still, I wasn't looking for a “melts-in-your-mouth” texture. I turned to my trusty copy of Harold McGee’s On Food and Cooking: The Science and Lore of the Kitchen, to learn about candies and jellies. From that reading I decided to add pectin and corn syrup. The next batch with these modifications was firmer and much more heat resistant.
When making gumdrops, the outside will be sticky and gooey, so the final step is to roll them in sugar. When I made my first batch I was concerned that a child or animal might find them and eat them. Borax is supposed to be basically harmless to mammals*, but, I wasn't 100% confident about that, and anyway, I wanted the gumdrops to stay where I put them so they would be eaten by ants, not by wayward kids. I figured that a sand coating would dissuade even the most intrepid sugar-fiend. Unfortunately, sand isn't as effective for this purpose as sugar, since sugar absorbs water while sand doesn’t. Coating the “gumdrops” in sugar draws out some of the water, making them firmer and making the coating stick better. Also, I didn't like dealing with the sand; somehow I ended up with sand everywhere. Like going to the beach, sand find its way into everything.
* According to Wikipedia, "...boric acid is poisonous if taken internally or inhaled in large quantities...5 to 20 g/kg has produced death in adult humans." The 3 tablespoons of boric acid in the recipe below weighs about 30g, so, eating the entire batch (yuck) shouldn't harm an adult. The Wikipedia article goes on to say that according to the ADTSR, "...the minimal lethal dose of ingested boron (as boric acid) was reported to be 2–3 g in infants, 5–6 g in children, and 15–20 g in adults." However, in reading the ADTSR report, I was unable to find those numbers. I suspect they may refer to long-term exposure. I would be eager to hear if anyone has any additional information on boric acid toxicology.
For the next batch I decided to have faith that the average child has better sense than to eat random gobs of goo lying on the ground. I also trusted in the claims of borax safety. This time I dredged the “gumdrops” in sugar. Ultimately I have chosen to store them in a plastic container filled with sugar to keep them dry and separated. This is working well. So far the “gumdrops” are staying solid and dry and none of the pieces that I have distributed have disappeared (other than through the slow chewing of ants.) Note however that if you have children or pets, you may want to use sand or dirt regardless of the benefits of a sugar coating.
Lastly, I have been playing around with the amount of borax in the mix. Ant poison is tricky - one wants to have the ants bring the poison back to the nest before dying, but, the poison must ultimately achieve a lethal dose. Too poisonous and the ants just eat and die. A few hundred dead ants is nothing to an Argentine ant colony. Too little poison and you are just giving the colony a sugary treat. The original liquid recipe called for approximately 16 parts water to 8 parts sugar to 1 part boric acid. I assumed that for a non-liquid approach the water was effectively irrelevant; what was important was the sugar to borax ratio of 8:1, or 2 tablespoons borax to 1 cup sugar. With this ratio it seemed like it was taking weeks for the ants disappear. I guessed that it takes ants much longer to eat a gumdrop and carry the pieces back to the nest than to simply suck up liquid poison. Since then I have kicked up the ratio to 8:1.5, or 3 tablespoons borax to 1 cup sugar. The ants are disappearing much faster now – hopefully the colonies are dying as well. If you try this recipe, please let me know how it works for you.
Please note: I am not a doctor, chemist, nor entomologist. The recipe I’m providing here is based upon my reading and experiences in my own yard, not on formal training. If you choose to make and use either of my ant poison recipes, you do so at your own risk. I provide no warranties either for safety or efficacy.
- Gelatin Mixture
- 1 envelope plain gelatin
- About 3.5 Tbs cold water (Just under 1/4 cup)
- Sugar Mixture
- 1/2 cup boiling water
- 7/8 cups sugar
- 1 Tbs corn syrup (light Karo)
- ½ Tbs pectin
- 3 Tbs borax*
- About 1/8 cup ice cubes
- Sugar (or Sand) for finishing gumdrops
Pour the cold water into a bowl. Sprinkle evenly with the gelatin and allow it to “bloom” while you prepare the sugar mixture.
In another bowl, mix the ingredients for the sugar mixture. Make sure the sugar and pectin are fully dissolved. If not, microwave for a minute and stir until dissolved. [Note: this is simplified from making confections for humans where proper boiling of the sugar mixture matters.]
Add the hot sugar mixture into the gelatin mixture. Stir until the gelatin is completely dissolved.
Add the ice cubes to aid in cooling. For a delicious gumdrop you wouldn’t want to do this – you would let the jelly solidify slowly. But, for ant poison there is no point wasting time. Allow to cool completely and become firm.
Carve out blobs of gelatin with a spoon and dredge in sugar (or sand if you are concerned about the gumdrops looking too tempting.) Store in a container until ready to use. For the first few days I leave the container open so some water can evaporate, then I seal it to keep them “fresh.” Note: may melt if place in hot location. If so, allow it to re-cool and reform “gumdrops.”