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Changing crop variety could extend biopesticide effectiveness

Changes to a pest's diet could slow the evolution of resistance to biopesticides, according to research from University of Stirling scientists.

It is hoped that the findings could allow the development of biopesticides that are effective for longer, potentially increasing food security, reducing damage to the natural environment and boosting agro-ecological biodiversity.

Researchers discovered that cotton bollworm pests—a species of moth that can cause considerable agricultural damage—show a great deal of genetic variation in how well they survive after being exposed to biopesticide fungi, which are often considered safer alternatives to chemical pesticides.

The study showed that exposure to biopesticide fungi might lead to the evolution of resistance, just as with synthetic pesticides, and builds on previous findings that indicated new approaches are required in managing resistance risks to greener pesticides.

However, alterations to the pest's diet, the crop it eats, had a greater impact on evolution of resistance than switching the type of pesticide used—meaning that the variety of crop grown could impact how quickly pests adapt to biopesticides.

Scientists from Stirling's Faculty of Natural Sciences, working with colleagues at the São Paulo State University (Brazil), and the University of Gothenburg (Sweden) raised thousands of cotton bollworm larvae in the lab from different family lines.

The team tested how well the larvae survived after being exposed to two different fungal pathogens, while feeding on tomato, maize, or soybean plants.

Research took place in controlled lab conditions at the University of Stirling using fungi sourced from Brazil with the support of international partners, and combined breeding experiments with advanced statistical modeling to uncover genetic patterns.

It builds on a study published in 2023 that showed insect pests that attack crops already carry many genes that improve their ability to combat infection, which could lead to resistance to greener pesticides.

Dr. Rosie Mangan, post-doctoral researcher at the University of Stirling, said, "This is a major insight because we have shown the potential for substantial evolutionary changes in surviving exposure to biopesticides—but also that farmers might slow this down by using more diverse cropping systems.

"Understanding how diet influences fungal biopesticides resistance helps inform smarter pest management strategies that are sustainable and less reliant on chemicals.

"Farmers and policymakers could use these findings to design pest control systems that keep biopesticides effective for longer, reducing environmental damage, helping promote agro-ecological biodiversity and improving global food security.

"These insights are especially relevant to agricultural policy in the U.K., EU, and other regions where biopesticide use is growing."

The new paper, "Crop diversity induces trade-offs in microbial biopesticide susceptibility that could delay pest resistance evolution," is in PLOS Pathogens.

Dr. Mangan worked on the study with Professor Matthew Tinsley and Ester Ferrari, of the Faculty of Natural Sciences at the University of Stirling, Dr. Luc Bussière of the University of Gothenburg, and Dr. Ricardo Polanczyk of São Paulo State University. The study formed part of a larger international initiative focused on making crop protection more sustainable.