Dicamba: A Menace to Monarchs

Majestic Butterflies At Risk From Widespread Spraying of Plant-killing Pesticide


Already imperiled by escalating pesticide use and other human activities, monarch butterflies’ epic annual migration across North America now faces a dangerous new threat. Take action now to help them.

This investigation is the first in-depth look at how the recent approval of dicamba — a drift-prone, plant-killing pesticide that's used on genetically engineered cotton and soybeans — will harm:

  • flowering plants that provide nectar for adult monarchs; and
  • milkweed, the only plant that feeds monarch caterpillars.

We were particularly concerned with examining the effects of the recently expanded use of dicamba, which is projected to increase by nearly 100-fold on cotton and soybean fields within monarch habitat by 2019.

Learn more about this map and watch our video on Facebook. (Note: Map is best viewed in Chrome or Firefox; may not display in Internet Explorer.)

This map shows the locations and timing of recorded monarch eggs and larvae during a representative year, along with the locations and timing of dicamba spraying periods for cotton and soybean crops nationwide. As time passes, the monarch egg and larva observations (white butterfly icons) begin to appear in accordance with their observation. The areas where cotton (yellow) and soy (red) crops are grown become visible when dicamba is anticipated to be sprayed.

We'd like to give a huge thanks to the team at Journey North and all the amazing citizen scientists who collected data used in our map.



Full report
Executive Summary
Methodology on Mapping
Methodology on Use Projections



Banner photo: monarch butterfly on milkweed, adapted from report cover