American scientists claim that neonicotinoid insecticides aimed at controlling crop pests, such as soil-dwelling grubs and maggots, could lead to increased slug populations and therefore reduced yields.
“Our research suggests that neonicotinoids can have unintended costs, even within crop production,” John Tooker, associate professor of entomology at Penn State University who led the project.
“In our lab work, we found that slugs were unaffected by the fungicides and also unaffected by the neonicotinoid insecticides, likely because they are mollusks and not insects,” said Tooker. “But the slugs did transmit the insecticide to the ground beetles, impairing or killing more than 60 per cent of the beetles.”
In the field, the team found that the neonicotinoid treatments depressed activity of insect predators, thereby relaxing predation of slugs and reducing soybean densities by 19 percent and crop yield by 5 per cent.
“Slugs are among the most challenging pests faced by Mid-Atlantic no-till growers,” said Tooker. “Our research reveals that neonicotinoids can indirectly increase slug damage to crops by poisoning insects that eat slugs. As a result, crop yields are lower.
“This phenomenon dispels the common belief in the United States that insect predators do not contribute to slug control,” he said. “It also emphasizes that if growers care for these predator populations they can help with slug control.”