The environmental organization Center for Food Safety is blaming agriculture giant Monsanto for declining numbers of monarch butterflies.
A new report finds that spraying glyphosate herbicide on Monsanto’s Roundup Ready crops has killed off sixty percent of the common milkweed since 1999.
John Pleasants at Iowa State University says milkweed is the only food source for monarch butterfly caterpillars.
“A huge chunk of the resource that would support these butterflies has disappeared. As you would expect, any population is sort of dependant on how much resource is available to it," he said.
Pleasants says monarch populations have declined by 90 percent since the mid-1990’s.
The U.S. Fish & Wildlife Service is considering listing the monarch butterfly as a threatened species.