I will be bringing a Nutritional Bundle and Carribbean Bundle to Boca Del Toro Island–Panama soon. (They arrived at my home safely yesterday!) The Community Garden leader wrote and said they are having trouble with leaf cutter ants devouring whole gardens in near by neighborhoods. Before we plant the new bundles there, could you give ideas for how to prevent leaf cutter ants from invading the new garden areas and how to control them in established gardens?
I’m not aware of proven tactics for deterring leaf-cutter ants from entering new areas. Perhaps mulching plants would deter them slightly from harvesting leaves, but they are aggressive and determined organisms. Perhaps increasing soil organic matter through composting or mulching over time would bring more balance to the soil community and bring in potential predators such as specific nematodes.
There has been a lot of research looking at control methods including application of parasitic fungi that kill the fungus that the ants are feeding/cultivating. The ants are really smart though and have been able to detect the parasitic fungi and remove it.
Here’s a pretty good article reviewing the above
I just looked in the book “Producing food without pesticides: local solutions to crop pest control in West Africa” by Lowell Fuglie in our library. It mentioned caster oil plant (Ricinus communis) as an effective control. It lists options for applying the plant parts. A spray can be made from soaking green leaves and seeds in water for a full day. After soaking, the solution is filtered and sprayed on target pests. Alternatively, the green seeds and leaves can be crushed into a powder that is then applied. Or seeds, leaves or oil cake can be mixed with the soil.
Caster oil may not be available in your region though, I am not sure.
I also found this open source resource that lists other tropical crops including neem and jack bean that negatively effect leaf-cutter ants. I have also heard that if you find a dead nest without ants in it anymore, you can take the soil from there and put it on an active nest and they will leave. I don’t know if it’s true or not. Has anyone else heard of this or tried it?
I know I’m a bit late to your question. I’ve have been experimenting with controlling leaf cutter colonies in Bolivia for a while now. I would be interested in hearing about things you have tried. What has worked for you and what has not.
I hope to write a more extensive piece on leaf cutters soon. They are an extremely challenging and complex problem to control. They learn very quickly and so it usually takes a lot of different approaches to control them. I’ll quick highlight some of the things I’ve found.
Cotton: For protecting specific plants, a ring of cotton or similar substance (fluff from Silk Floss Trees, Ceiba species) gets caught in their feet so they hate crossing it. If you can tie it to the trunk of a tree it works best and down in the soil it gets matted down quickly.
Clutter their highway: You may have noticed they like neat, clean highways to their collections sites. Make your plants as hard to get too as possible: messy thick fibrous mulch, perennial peanut, water/oil barriers, etc.
Diverse/balanced ecosystem. They love a high diversity and density of plants to choose from. If you have a large wild space for them to choose from, it helps keep them away from your garden. Also having a high density and diversity in your garden spaces will help ensure that you don’t loose everything.
Distractions: You can specifically plant plants they really like to help distract them from your other plants. In my area they love Moringa, especially Moringa stenopetala. If you can protect the trees until they are fairly mature, they seem to be able to take a lot of damage from leaf cutters and then the ants leave many of your other plants alone. Putting a compost pile nearby also works. They love to walk off with your plant scraps.
-Poison: Poison doesn’t often work well because their colonies are huge and they don’t eat the poison like most ants. They eat the fungus they grow in their gardens underground. So killing the fungus is the goal but very difficult. Plants like Jack Bean and Sesame will kill their fungus however as soon as the ants catch on, they will never touch those plants again. Similarly with man-made poisons, they learn fast and will never touch it again.
-War/Peace: So I tend to make peace with them during wet season. They have lots of food to pick from and intentionally feeding them their favorites during this time keeps them away from my garden. During dry season however, food for their fungus becomes more scarce and they start taking everything in site. They are also most vulnerable during this time. This is when I launch all out war on them to try and knock the colony back. Boiling water down their nests, dropping toxic plants around their nest, encouraging nearby colonies to fight with each other, releasing natural predators or parasitic fungal spores, etc.
That is a quick overview of what I’ve found. I hope to write up more info on this topic soon as it has been one of my biggest problems working in South America. I’d love to hear more about what you have tried!