Chemical Warfare Under Study was originally published in the BFEC Newsletter, Vol. 12/No. 1, Winter 2008.
Garlic mustard is a biennial that was first brought to North America by European settlers as a medicinal and culinary herb in the 19th century. It has quickly become invasive, dominating habitats at the expense of wildflowers. At the BFEC, winter is a perfect time to become acquainted with the plant, which can be seen overwintering among the decaying leaves along forested trails.
Recently, researchers have found that one of the keys to garlic mustard’s invasive success may lie below ground. The roots of most species of plants are associated with soil fungi known as mycorrhizae. This mutually beneficial relationship is maintained by a sort of biochemical trading agreement: the fungi help the plant roots take up nutrients and water from the soil, and in return, the plant provisions the fungus with sugars. However, like all members of the mustard family, garlic mustard goes it alone by releasing chemicals into the soil that kill the fungi, which has been found in greenhouse studies to reduce the growth of hardwood seedlings by up to 70 percent.
Professor of Biology Andrew Kerkhoff, along with biology majors Ellen Thompson ’08, Amy Kessler ’09 and Kaleb Keyserling ’09 began experiments last summer to examine if these effects could be observed in the field. Over 320 seedlings were planted for the experiment and cages were built around them to protect them from deer. Garlic mustard was removed around half of the seedlings and left in place around the others. Preliminary study results indicate that garlic mustard did impact growth of sugar maples but not the oaks. Measuring the impacts of an invasive exotic is not only critical for developing effective management strategies, it also provides an opportunity to better understand the intricate inner workings of forest ecosystems.