But leaves are a pretty diffuse energy source, so the ants need a lot of them to grow enough fungal food for themselves. The ants prefer leaves that have low amounts of cellulose and therefore high amounts of cell contents. These leaves are easier to cut and pack more nutrition per piece of leaf for the fungi. With their filmy, highly nutritious leaves, moringas are the perfect food for leafcutters. In a single night they can defoliate a whole tree. At the moment, many of the plants in the moringa germplasm collection are small. As a result, a little distraction on our part can mean finding the plants defoliated in the morning. Given that many of the species, at least the small northeast African ones, often grow only in short pulses, a defoliation can set them back a good six months. Even the large, continuously growing species like Moringa hildebrandtii get their growth slowed down from a complete defoliation.
So every night it’s up to the collection with a flashlight. When we find ants carrying leaves, we follow them to find the nest. This is sometimes hard because the ants often nest under piles of debris or travel far from the nest, and come in from well outside the collection lot. One of the ongoing tasks these days is clearing the piles of sticks that then get covered with vines, and under which the ants like to nest, precisely to make spotting anthills easier.
Once we find a nest, it’s time to poison the ants. The cleverest method we use is an insecticide that here is sold as Trompa. It comes in long, slender dark pellets that are impregnated with a bait. This bait odor is irresistable to the ants, and they instantly swarm out to take the pellets down into the anthill. They seem to like the odor so much that they even do this in the day sometimes. Once they have the pellets down in their underground chambers, the humidity vaporizes the poison, apparently abamectin, in the pellets, gassing the ants in their homes. The next night there are usually just a few ants around the hill, and after a little more Trompa the colony is finished. Trompa seems sensitive to temperature, and if it gets a little warm or the jar gets some direct sunglight, the pellets lose their dark color and turn a light tobacco. These pellets are always ignored by the ants. So we also use powdered pyrethroids as a backup. It would seem like it would be less effective, given that the ants do not carry it down into their nest. But a generous dusting around the entrance of the nest does seem to kill all of the ants in one or two days, because after dusting there are no more ants to be seen.
Once the trees get bigger, a few leafcutters won’t make much of a difference. But for now, while they’re small, it’s us or the ants.