Ants may be more effective than pesticides at helping farmers produce food, according to new research. They are better at killing pests, reducing plant damage and increasing crop yield, according to the first systematic review of ants’ contributions to crop production.
Ants are generalist predators, preying on pests that damage fruits, seeds, and leaves, leading to a drop in crop yields. A greater diversity of ants generally provides greater protection against a wider range of pests, the study finds.
The analysis looked at 17 crops, including citrus, mango, apple and soybeans in the US, Australia, UK and Brazil, among others. “In general, with good management, ants can be useful pest control and increase crop yields over time. Some ant species have comparable or higher efficacy than pesticides, at a lower cost,” researchers wrote in the article published in Proceedings of royal society b.
The Brazilian team looked at 26 species, most of them arboreal ants, that nest on plants or on the ground, but often climb on plants. They found that ants do best in diversified farming systems such as agroforestry (where trees and crops are grown on the same land) and shade-grown crops because there are more breeding grounds and food sources for them.
Principal investigator Dr. Diego Anjos, from the Federal University of Uberlândia, said: “Our study encourages farmers to use more sustainable practices, such as biological control by ants and shady crop practices as a way to naturally promote ants in crop systems.”
The role of ants in agriculture is not yet fully understood as they can also pose a problem. Pests such as mealybugs, aphids and whiteflies, which produce a sugary water called honeydew, are generally more common when ants are around. This is because the ants feed on honeydew, thus essentially “growing” aphids like livestock, protecting them from predators in return.
Researchers say conservation-friendly management practices, such as providing an alternative source of sugars (on the ground, by the trunk of a tree, or on its branches), can disrupt this relationship. The ants are distracted and can continue to reduce the number of other pests such as caterpillars and beetles, which do not produce honeydew.
The paper looked at most insect species considered pests around the world, with 30 species in 52 studies. The data came from studies comparing groups of plants with ants set against plants from which the ants had been removed (mechanically or chemically), strongly suggesting that the ants were responsible for the observed changes.
There are more ants than any other insect, and they make up half of the insect biomass on Earth. At least 14,000 species of ants are known, and many more are likely to remain unknown. Citrus growers in China have used ants in agriculture for centuries, and the insects have also been used to control forest pests in Canada, cocoa pests in Ghana and crop pests in Nigeria.
Ants found on Fiji’s Pacific islands can breed and breed at least six plant species, as part of a mutually beneficial relationship dating back 3 million years, according to research published in Nature.
dr. Patrick Milligan, of the University of Nevada’s Pringle Lab, was not involved in the study, but said the findings were “both encouraging and not at all surprising.” He added: “They provide a neat and tidy description of ant-derived benefits that are ubiquitous in ecological and agricultural systems.
“This is essentially another option in our farming toolset that allows farming to move away from pesticides — which really harm neighboring insect communities — but still improve crop yields.”
Prof Adam Hart of the University of Gloucestershire, also not involved in the study, said it was confirmation of the important role ants play as pest controllers. “Many of us have talked about ants as natural pest control agents. But as with anything, it’s usually more complex than we think once we dig deeper.
“The research suggests it can be profitable to move ant colonies into agricultural areas and do things to encourage the presence of ants. However, we have to be careful – it’s not all ants or all crop systems, and they can come at a cost. It’s all about developing a better understanding of how ants interact with pests and other organisms.
“An important message for me is that we need to understand even more about small-scale interactions if we want to farm better. In other words, we need more ecologists.”