Their numbers already in a free-fall due to escalating pesticide use and other human activities, monarch butterflies face renewed threats in North America, where 60 million acres of habitat — an area larger than the state of Minnesota — will be sprayed with an herbicide that kills the milkweed monarch caterpillars need to survive, according to a recent study.



Monarch butterflies were once so plentiful in their winter groves that the sound of their wings resembled a rippling stream or summer rain, according to the Center for Biodiversity. Their populations have plummeted 80 percent over the last two years, and the recent approval of the drift-prone, plant-killing herbicide dicamba could drive them further to extinction, according to the environmental group's recent study. The chemical also kills the flowering plants that provide nectar adult monarchs need to stay alive as they make their epic, 2,000-mile migration from Canada to Mexico.

By 2019, the use of dicamba is expected to increase 100-fold — or 57 million pounds annually — on cotton and soybean fields located in areas frequented by monarchs. In the report, A Menace to Monarchs, the Center for Biodiversity said the decline in monarchs in recent decades has coincided with the surge in crops genetically altered to tolerate glyphosate, which triggered the decline of milkweed and the proliferation of glyphosate-resistant weeds resistant to the chemical across millions of acres in the Midwest. In response, farmers began using dicamba, approved by the U.S. Environmental Protection Agency in 2016, to combat glyphosate-resistant weeds.

That puts monarchs in even more peril. The group cited research that shows just 1 percent of the minimum dicamba application rate would reduce milkweed habitat by 50 percent, even more so than glyphosate. Photo by Beth Dalbey/Patch The report also said the timing of dicamba application occurs when monarch egg and caterpillars are found on milkweed, which is an essential resource for monarch reproduction.



The group said that even when applied at permissible levels, dicamba will have serious and far-reaching consequences for monarch butterflies, their habitat and the ecological health of vast areas of the country.

It recommends that when the when EPA registration of dicamba on genetically engineered cotton and soybeans expires in late 2018, continued use should not be approved.

5 Things You Can Do As spring approaches, here are some monarch-friendly things you can do in your garden: 1. Plant milkweed: There are many milkweed species found in North America. Click here to find out what milkweed species will grow in your area.