Invasive Plant News

The Midwest and Great Lakes Chapter of the Society for Ecological Restoration (SER) had its chapter meeting at the University of Michigan in Ann Arbor earlier this month.  These conferences are wonderful mix of presentations - by students, professors, lay-people, not-for-profit leaders and business representatives. 

Participants got a closer look at the eastern massasauga rattlesnake. Photo by Stephen Glass

I have been to conferences and meetings of all kinds. It always impresses me how lively, open and welcoming these SER chapter meetings are.  Student presentations and posters draw the same attention (and hard questions) as given to presentations of established experts.

One of the highlights of the conference was a visit to the Matthaei Botanical Gardens.

An eastern massasauga rattlesnake lying in the grass. Photo by Stephen Glass.

A major part of the Gardens have been restored to provide habitat for the eastern massasauga rattlesnake (Sistrurus catanatus catenatus), a protected species in Michigan. This restoration effort is a complex undertaking. Restoration techniques have to be adjusted and customized. For example, in many areas the snake uses habitat that includes non-native bluegrasses (Poa compressa, P. pratensis). Only after sufficient area of more mature native prairie habitat has been created can the bluegrass dominated areas also be converted to native prairie. In fact, the area where we saw the snake was dominated by bluegrasses.

The Annual Meeting Committee deserves enormous credit for putting on a great meeting and recruiting those eastern massasauga rattlesnakes that made their appearances! The Committee members include:

• Young D. Choi, Purdue University Calmulet (chairperson)
• David Benson, Director of Environmental Studies and Assistant Professor of Biology, Marian College
• Hua Chen, Associate Professor of Biology, University of Illinois, Springfield
• Cody Fleece, Stantec Consulting Services
• Robert Grese, Professor and Director of the Matthaei Botanical Gardens and Nichols Arboretum. University of Michigan
• Jennifer Lyndall, ENVIRON International Corporation
• Pamela Rice, PR Environmental Consulting
• Rocky Smiley of the USDA ARS Soil Drainage Research Unit
• Donald Tilton, Environmental Consulting & Technology, Inc.

A recent article in the Star Tribune, a Minnesota newspaper, highlights two related risks of pesticide applications – drift and volatilization.  The article doesn’t deal with invasive species, and the chemical of concern is a fungicide, not an herbicide.  Nevertheless, the article does point out the importance of controlling drift and volatilization from pesticide applications – which of course are commonly used to control invasive species.

The investigation was spearheaded by the Pesticide Action Network (PAN) and concerned the use of the fungicide chlorothalonil on potato crops.  In an effort coordinated by PAN, residents near potato fields in northwestern Minnesota set up and checked 19 monitors at schools, in yards, and on porches.  The monitoring revealed low concentrations of the fungicide in the air in and around the town of Perham, Minnesota, 68 percent of the time during the monitoring period. 

One troubling aspect is that the concentrations of the fungicide in the air appear to have resulted from legal applications of the fungicide according to Linda Wells, the Midwest Coordinator for PAN of North America.  It appears therefore that the chlorothalonil moved off-site some time after application such as by volatilization, i.e., the fungicide changed to a gas after application.  This is concerning because it may be hard to correct the problem.

The United States Environmental Protection Agency (EPA) is currently reviewing health risks from the inhalation of chlorothalonil.  In addition, EPA’s Office of Research and Development has launched a research program to assess Drift Reduction Technology.   

However, until EPA acts, officials at the Minnesota Department of Agriculture, indicate there are few options.  This is troubling since Minnesota state health officials find the data credible.  The Star Tribune article quotes Rita Messing, a toxicologist with the Minnesota Department of Health’s division of environmental health who is familiar with the findings.   Messing says “We are inclined to believe it until there is other data that is better.”

Invasive plants take advantage of late

Common buckthorn (Rhamnus cathartica),forming grean background, retains its leaves late into the fall.

season photosynthesis by keeping their green leaves later in the fall than native plants.  This is the finding of a recent study by Jason Fridley published online in Nature.  The study compared related deciduous species such as Japanese honeysuckle (invader) and Canada honeysuckle (native), burning bush (invader) and bursting heart (native), and European buckthorn (invader) and Carolina buckthorn (native).

 According to Fridley, this concept “was totally off of everybody’s radar.”  However, anybody who has worked to control an invasive species like common buckthorn (Rhamnus cathartica) has long known that this late season persistence makes the non-native easy to identify for treatment.  Common buckthorn is the tree with green leaves in the late fall.

What’s new that the study offers is that these invaders continue to photosynthesize for almost four weeks longer in the fall than their native counterparts.   It is not certain that this gives the non-native species an advantage.  For example, the non-natives lose a source of nitrogen when their green leaves fall off before nitrogen still in the green leaf is absorbed into the stem and roots.  According to Fridley, the invaders may have co-evolved with another invader, Eurasian earthworms, which speeds decomposition of leaves  and may bring the nitrogen back into the invasive plant.

 I don’t find this hypothesis convincing (although I have no data to back up my position).  I have seen common buckthorn thrive in sandy soils with few earthworms.  Couldn’t it just be that an invasive like buckthorn gains more by photosynthesizing longer than it loses by dropping green leaves?  Each year as the growing season extends due to global warming, invasive species such as buckthorn improve their advantage.

An opinion piece in the Canberra Times by Julian Cribb, an Australian science and agriculture writer, paints this bleak image of the future of the Austrailian natural world:

“By the end of this century it is possible that Australia will be gone for good, immersed in a green tide of alien vegetation, pests and shifting climatic regions. It may well still be sunburned and afflicted (more frequently) by drought and flooding rains, but the quintessential Australian landscape that has defined this continent for millions of years and was the backdrop to both Aboriginal and European settlement, will largely no longer exist.”

Cribb attributes a major role in this transformation to the more than 30 new alien species of plants and pests introduced every year in Australia.  Is the future this bleak in Australia?