By Blake Jackson
A study from Penn State researchers indicates that while insecticides protect crops from pests, they might also increase certain weed populations.
This is especially true when compared to Integrated Pest Management (IPM), which uses insecticides only when necessary.
The study also examined the impact of cover crops on this dynamic. Researchers found that after three years, fields treated with preventative insecticides and without cover crops had more weeds, particularly marestail. However, cover crops mitigated this issue, even in insecticide-treated fields.
"Always using an insecticide at planting does not seem to be the best approach in Pennsylvania considering that early-season insect pests tend to be a relatively uncommon problem," said John Tooker, a professor of entomology. "When taking an IPM approach, we advocate for using the right products at the right time to control the right pests, and that will also then help reduce these negative consequences of using these treatments too much."
"Many of the seeds growers use were developed to not be killed by herbicides," said Elizabeth Rowen, lead author and assistant professor at the University of California, Riverside. "This allows growers to use glyphosate to control weeds; however, this also results in the evolution of herbicide-resistant weeds, which makes it much harder to control weeds without killing the crops. So, having multiple strategies to help manage weeds is really important."
Insects like beetles and ants eat weed seeds, offering natural weed control. Insecticides can disrupt this balance.
The study involved corn and soybean plots at Penn State’s research center. Researchers tested preventative insecticides, IPM, and no insecticides, with and without cover crops, over three years. They monitored factors like weed populations, insect communities, and crop productivity.
Tooker believes IPM can benefit large-scale growers. "Oftentimes corn and soybean fields are so big that growers are inclined to do all of the management up front so they don't have to go back and walk the fields," he said. "But our evidence suggests that walking these fields to identify problems as they happen can provide clear benefits in terms of not needing certain pesticides, namely many of the fungicides and insecticides."
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Categories: Pennsylvania, Crops, Education