Report: 60 Million Acres Of Monarch Habitat To Be Doused With Weed Killer

Within the next two years, more than 60 million acres of monarch habitat will be sprayed with a pesticide that’s extremely harmful to milkweed, the only food for monarch caterpillars, according to a new analysis from the Center for Biological Diversity.

Monarch populations have fallen 80 percent in the past two decades due to escalating pesticide use and other human activities, according to CBD. The center’s new report, A Menace to Monarchs, illustrates how the butterfly faces a new threat from accelerating use of the drift-prone and toxic weed killer dicamba across an area larger than the state of Minnesota.

“America’s monarchs are already in serious trouble, and this will push them into absolute crisis,” said Nathan Donley, a senior scientist at the center. “It’s appalling that the EPA approved this spraying without bothering to consider the permanent damage it will do to these butterflies and their migration routes.”

The report released this week found that by 2019, use of dicamba will increase by nearly 100-fold on cotton and soybean fields in the monarch’s migratory habitat across the heart of the United States.

Other key findings include:


  • In addition to 61 million acres of monarch habitat being directly sprayed with dicamba, an additional 9 million acres could be harmed by drift of the pesticide.
  • The timing and geographical distribution of dicamba use coincides with the presence of monarch eggs and larva on milkweed.
  • Dicamba degrades monarch habitat by harming flowering of plants that provide nectar for adults as they travel south for the winter and by harming milkweed that provides an essential resource for reproduction.
  • Research has shown that just 1 percent of the minimum dicamba application rate is sufficient to reduce the size of milkweed by 50 percent, indicating it may have a greater impact on milkweed growth than the already widely used pesticide glyphosate.

The Environmental Protection Agency in 2016 approved new dicamba products for use on genetically engineered cotton and soybeans.

In 2017, there were reports of at least 3.6 million acres of off-target, dicamba-induced damage to agricultural crops and an unknown amount of damage to native plants and habitats, including forests.

“There’s no question that use of dicamba across tens of millions of acres will deepen risks to our dangerously imperiled monarch populations,” Donley said. “When dicamba’s use on GE cotton and soybeans comes up for reapproval later this year, the only responsible thing for the EPA to do is allow that approval to expire.”

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