Insecticides may increase marestail weed growth, study finds

A new study suggests that insecticides, while intended to protect crops from pests, might actually lead to an increase in certain weed populations. Researchers from Penn State conducted the study and their findings were published in the journal PeerJ. The study compared two approaches: using insecticides preventively at planting and using an integrated pest management (IPM) strategy. The IPM approach applies insecticides only when pests are present. The researchers also looked at the impact of cover crops, which are grown to protect soil after harvesting. They discovered that fields treated with insecticides, but without cover crops, had more weeds, particularly marestail, after three years. However, adding cover crops successfully prevented this increase in weeds, even in those fields. Professor John Tooker, one of the authors, noted that the likely reason for these results is that insecticides may also kill beneficial insects that control weeds. He advised growers that using insecticides preventively at planting may not be the best strategy, as early-season insect pests are often rare. Elizabeth Rowen, the lead author, highlighted the importance of diverse weed management strategies, especially because many weeds are becoming resistant to glyphosate, a common herbicide. She mentioned that insect pests like beetles and ants can help control weeds, but insecticides may harm these helpful insects too. For their research, the team studied corn and soybean plots over three years, testing various treatment plans. They measured factors such as weed populations, insect communities, and crop productivity. Tooker emphasized the benefits of the IPM approach, stating that regularly monitoring fields for problems can reduce the need for certain pesticides. The research was supported by the U.S. Department of Agriculture and indicates that a careful pest management strategy can be beneficial for crop producers.