One Farmer’s Pest Is Another Farmer’s Pesticide: Ants Excel at Killing Other Bugs

The research is the latest to show that ‘beneficial insects’ can help reduce the use of chemicals in agriculture.

Weaver ants. (Photo: Flickr)

Sep 4, 2015· 2 MIN READ
Tove Danovich is a journalist based in Portland, Oregon.

There’s a reason why the lowly ant is one of the few insects to have achieved superhero status on the big screen. Ants are incredibly strong for their size, work together to do everything from feeding and building the colony to enslaving other ants, and use chemicals to communicate with one another. Now, ants may bring their superhero skills to the real world, providing sustainable pest control on farms.

A new study in the Journal of Applied Ecology found that not only were ants able to lower pest populations on many crops but that could also lead to a higher harvest as a result. Joachim Offenberg, the study’s author, mostly focused on weaver ants but writes that these ants, found in parts of Africa, Asia, and Australia, “share beneficial traits with almost 13,000 other ant species and are unlikely to be unique in their properties as control agents.”

The steps a farmer needs to take before the ants will go to work are fairly simple. In the case of weaver ants, which live in trees, farmers have to first install the colonies and then provide a means of “transportation” between one tree and another. This can take the form of strings or poles. The trees also have to be pruned to keep neighboring ant colonies from finding and attacking one another. From there, farmers just need to wait for the ants to kick any intruding pests out of their new home.

Offenberg points out that ants comprise “one third of all insect biomass,” and ants live on every continent except Antarctica, making it easy to find a local species that will work for the farmer. As anyone whose backyard barbecue or picnic has been interrupted by ants knows, there are plenty of them to go around. Their ability to communicate and work together, in addition to their somewhat territorial nature, also makes them likely to attack a wide range of other insects. And they’re cheap. On an Australian cashew plantation, setting up ant colonies costs about half as much as chemical insecticides, while “yields were 49 percent higher.”

Using natural predators to control harmful pests is not a new philosophy—Chinese citrus farmers used ants to protect their orchards as early as 300 B.C. Ladybugs are often employed by backyard gardeners to control aphid problems. Wasps can be used to fight off caterpillar problems. Starting in the 1950s, when the modern era of chemical-heavy farming began, agricultural departments started getting more serious about using natural pest controls, developing both biological controls and the more ecology-focused integrated pest management approach. Predator insects have averted a number of agricultural disasters over the years.

In 1986, The Associated Press reported that wasps had been employed to curb populations of the über-destructive alfalfa weevil in the Northeast. Between 1959 and 1980, the use of these wasps caused a 73 percent decrease in the use of chemical pesticides and a savings of $8 million a year. In some states, wasps cut out the need for other forms of pest control entirely.

Even further back, in the 1880s, a small pest known as the cottony cushion scale attacked California’s citrus industry with a vengeance. The University of California’s Department of Agricultural Resources notes, “Efforts at controlling this pest resulted in one of the earliest and most impressive examples of classical biological control.” Imported all the way from Australia, the vedalia beetle, the cottony cushion scale’s natural enemy, managed to save the orchards and is still employed today.

With more than 5 billion pounds of pesticides used around the world in 2007, and around 20 percent of that being applied in the United States, integrated pest management is by no means about to disrupt chemical pest controls—but with increased understanding of the damage that pesticides can have on wildlife and humans alike, using ants instead of sprays starts looking preferable.

The main issue with using natural predators in modern agriculture is that they can also be affected by the application of chemical pest controls. Insect growth regulators or the neonicotinoids that are so harmful to honeybee populations, can kill off “good bugs,” leaving room for the bad ones to take over once again. In the case of ants, there is still a long way to go in testing best management practices. However, Offenberg mentions that in developing countries where farmers often have more time than money, a low-cost option that requires some tweaking and observation could be a perfect solution.