A New Hampshire Agricultural Experiment Station researcher has launched a study to determine if pesticide seed treatments inadvertently protect weed seeds in the soil from being attacked by naturally occurring invertebrate and fungal species. That’s a mouthful, yes, and the primary target of the research is food crops. But there’s a lot to be learned about the possible transfer of compounds to beneficial organisms, many of which support the health of ornamental plants.
“A host of insects and microbes that live in and on the soil, perform beneficial services that that we often fail to appreciate, including suppressing weed populations. By attacking weed seeds in the soil, these beneficial organisms help to reduce the numbers of weeds in a crop field that then need to be controlled through other means, such as with tillage or herbicides,” said experiment station researcher Richard Smith, UNH associate professor of agroecology.
According to a release from the Experiment Station, UNH researchers will investigate the role pesticide seed treatments play in mediating weed population and community dynamics, identify likely mechanisms contributing to the impacts of such treatments on weeds and their natural enemies, and explore whether cover crops, coupled with additional integrated pest management tactics, can mitigate nontarget effects of pesticide seed treatments on weeds.
“We have data suggesting that the insecticides and fungicides coated on most corn and some soybean seeds, generally referred to as pesticide seed treatments, can exacerbate the weed challenges faced by farmers. We hypothesize that pesticide seed treatments protect weed seeds in the soil from attack by their invertebrate and fungal ‘natural enemies,’ and we have preliminary data supporting this,” Smith said.
“We also have data indicating that noncrop plants, such as cover crops, can take up significant quantities of residual pesticides from the soil, suggesting that strategic planting of cover crops could mitigate spill-over effects of pesticide seed treatments on weeds, including those resistant to glyphosate,” he said.
Glyphosate-resistant weeds are a serious concern in many regions of the United States, and this has prompted many farmers to seek alternative ways of managing these weeds, including by enhancing populations of organisms that naturally kill weed seeds. “If pesticide seed treatments are facilitating the persistence of weed seeds in the soil by protecting them from attack by beneficial organisms, whether that be on farms in the Corn Belt or here in New Hampshire, that’s a problem we really need to figure out how to address,” Smith said.
The study is being funded in part by a grant from the USDA’s National Institute of Food and Agriculture; funding was made possible through the program’s Agricultural and Food Research Initiative program, which was authorized by the 2014 Farm Bill