Sandra Fischer recommends critical timing of milkweed mowing to extend breeding habitat
Keene, NH – Antioch University New England (AUNE) alumna Sandra Fischer, MS ’07, has discovered important new information that has the potential to help save the monarch butterfly from extinction. The research she conducted for her master’s degree in environmental studies revealed that the timing of milkweed mowing is critical to the monarch’s breeding habitat and survival. Her findings were recently published in the April 2015 issue of the scientific journal, American Midland Naturalist, in an article called “Enhancing Monarch Butterfly Reproduction by Mowing Fields of Common Milkweed.”
Photo: Ernest Williams
The article is co-authored by Dr. Peter Palmiotto, director of conservation biology at AUNE; Dr. Ernest Williams, professor emeritus at Hamilton College in New York; and Dr. Lincoln Brower, professor emeritus at the University of Florida and research biology professor at Sweet Briar College in Virginia. Now 83, Brower has spent his lifetime studying monarch butterflies, and is considered the world’s foremost authority.
“This journal article is derived from Sandra’s master’s thesis research at AUNE,” Palmiotto said. “It provides valuable new information for the conservation of this potentially endangered species and phenomena. That being a species that over multiple generations migrates each year from Mexico to Canada and back. By mowing portions of fields no later than early to mid-July we can sustain a more continuously suitable habitat for monarch reproduction.”
In the past 20 years, the once thriving monarch butterfly population has dramatically declined by 90 percent, and is being studied by the U.S. Fish and Wildlife Service for protection under the Endangered Species Act. Most monarchs are born in the Midwest. In the mid-1990s, they numbered one billion, but only 35 million survived last winter. Their rapid disappearance is attributed, in large part, to genetically engineered soybean and corn crops in their natural Midwest habitat. Those crops are engineered to be resistant to Monsanto’s Roundup herbicide, which kills milkweed plants, the monarch caterpillar’s only food source. It has destroyed more than 165 million acres of the butterflies’ habitat, including nearly a third of their summer breeding fields. Besides herbicide use, the monarchs are at risk from other pesticides, global climate change, drought and heat waves, urban sprawl, and logging on their Mexican wintering grounds.
In 2006, Ms. Fischer conducted her research in upstate Columbia County, New York. Strips were mowed in fields in early July, late July and mid-August, and compared to an unmowed control. Later, common milkweed (Asclepias syriaca) was monitored from July 29 through September 24 for plant height, vegetative stage, herbivory level, condition, monarch eggs and larvae, and the position of eggs on leaves and stems.
Fischer’s study concluded that mowing in July spurred the regrowth of milkweed, and sustained a suitable habitat for monarch breeding and hatching. August mowing proved to be too late. Additionally, more eggs were laid on the resprouted milkweed than on the older, taller control plants, and the overall condition of the milkweed plants varied with the time of the mowing. Her findings proved that timing of mowing is critical to extend the monarch’s breeding season and increase overall monarch reproduction. The timing of field mowing may be a key to sustaining monarch population but would need to be determined for each milkweed species across the country.
The full article, “Enhancing Monarch Butterfly Reproduction by Mowing Fields of Common Milkweed” can be read in the April 2015 issue of American Midland Naturalist, volume 173: pages 229-240.
For details, contact Peter Palmiotto at [email protected] or at 603-283-2338.
