Pest control is especially important on farms. It costs a lot of money, and if you overdo it on pesticides, you can seriously disturb nearby ecosystems. A new report lays out simple actions farmers could take to increase biodiversity and foster interactions between insect species to help keep pests under control.
"Our research suggests that agronomic practices that promote high levels of ... diversity fundamentally require fewer agronomic inputs," such as pesticides, write Jonathan Lundgren, an ecologist at the United States Department of Agriculture's Agricultural Research Service, and Scott Fausti, a professor of economics at South Dakota State University.
It wasn't just species diversity that mattered for pest control, but also the structure of interactions between insects.
To get a handle on how the insect population as a whole might impact pests, Lundgren and Fausti inventoried 106 insect species—a total of more than 37,000 individual insects—on 53 corn farms in the Northern Great Plains. Based on that collection, they computed each farm's species diversity, a particular measure of biodiversity that incorporates the number of species present, as well as how evenly each species is represented. For example, even if Lundgren and Fausti found 100 species on one farm, they wouldn't call it diverse if 99 percent of individual insects were common black ants.
The more diverse the insect population was, the fewer pests Lundgren and Fausti found. But the researchers didn't stop there, choosing instead to examine networks of interactions between species. Lundgren and Fausti built those by looking for correlations between species—that is, how often the same species showed up on the same farms. The pair constructed 10 such networks, each for a different level of pest abundance. The first network, for example, represented links between insects found on the five farms with mildest pest infestation.
Analyzing those networks revealed that it wasn't just species diversity that mattered for pest control, but also the structure of interactions between insects. As the average number of links between insect species increased, for example, the abundance of pests decreased. Similarly, farms had the fewest pests when insect species had about the same number of links to each other.
The results, Lundgren and Fausti write, suggest a new way of looking at pest control. "The importance of the association of biodiversity and ecological network structure with low pest populations provides goals that can be targeted with sustainable cropping systems that require minimal inputs for pest management," the researchers write today in Science Advances. In particular, they suggest, farmers could use less insect-lethal strategies, like simply tilling the soil less or planting a wider variety of plants to preserve insect biodiversity without sacrificing crop yields.
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