Category: Mexico, Monarch Butterfly

Nature’s Pharmacy: Using Milkweed to Fight Disease

 |  Mark D. Hunter
Image courtesy of Nina Markiw, Vermont Woods Studios

How Monarch Butterflies Use Milkweed to Fight Disease

Did you know monarch butterflies can self-medicate? Just like we head to the pharmacy during cold and flu season, monarchs turn to nature’s medicine cabinet–milkweed!

Monarchs and Their Natural Medicine

Monarch butterflies are vulnerable to a harmful parasite called Ophryocystis elektroscirrha (OE). But here’s the incredible part: some species of milkweed contain powerful compounds called cardenolides that help monarchs fight back.

  • Cardenolides are natural chemicals found in milkweed that can protect monarchs from predators and parasites.

  • When monarchs eat milkweed rich in these compounds, infected butterflies live longer, fly farther, and produce more offspring.

  • Even more amazing—infected monarch mothers choose to lay their eggs on species that offer the strongest medicinal benefits. This gives their caterpillars a healing head start.

Green Milkweed

Why Variety Matters

If toxic milkweed is so helpful, why don’t monarchs always use it?

Because medicine has side effects—for us and for butterflies. Healthy monarchs that consume high levels of cardenolides may grow more slowly or have fewer offspring. So, like us, monarchs use stronger medicine only when they need it.

That’s why planting a diverse mix of native milkweed species is so important. It allows monarchs to choose the right plant for their needs.

Climate Change is Changing the Medicine

Rising temperatures, changing rainfall, and increased carbon dioxide are already affecting the chemistry of milkweed plants—reducing their medicinal strength. This threatens monarchs’ ability to self-medicate and survive.

Community members planting trees in the Monarch Butterfly Biosphere Reserve Buffer Zone.

How You Can Help

  • Plant a variety of locally native milkweed species. Different types provide different medicinal benefits.

  • Avoid using pesticides in your garden.

  • Support conservation efforts that protect monarch habitat and restore native plant diversity.

By making your garden a diverse and welcoming space, you’re giving monarchs the tools they need to stay healthy and thrive.

Learn more about pollinator gardening and health:

Optimizing Milkweed in Gardening

Preparing Your Pollinator Garden for Spring

Urban Pollinator Garden

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Mark Hunter Headshot
Mark D. Hunter
Mark D. Hunter is the Dean of the Odum School of Ecology at the University of Georgia. Most recently he served as the Earl E. Werner Distinguished University Professor Emeritus of Ecology and Evolutionary Biology at the University of Michigan. He received his bachelor’s degree in 1984 and his doctorate in 1988, both from the University of Oxford in England. After serving as a NATO International Fellow and an NSERC International Fellow, he joined the faculty of the University of Georgia in 1995 where he served as founding Director of the Center for Biodiversity and Ecosystem Processes. He joined the University of Michigan in January 2006. His research interests include pollinator declines, forest ecology, environmental change, plant-animal interactions, ecosystem ecology, and biodiversity. Professor Hunter has published over 170 research articles and written or edited six books. He is the recipient of both a CAREER Award and an OPUS Award from the National Science Foundation, and in 2014 was elected a Fellow of the Ecological Society of America. From 2007 to 2012, he served as the first Director of the award-winning Frontiers Master’s Program in Ecology and Evolutionary Biology, which fosters graduate student diversity at the University of Michigan. Mark joined our Board in 2022.