The speaker was Dr John Madsen, professor of biology at MSU, who specializes in aquatic plant management. A web site on his publication can be downloaded from the web at: www.wes.army.mil/el/elpubs/pdf/mpe100-1/pdf.
The major weed concerns in Minnesota for exotic (non-native) species which can invade lakes are: Eurasian Watermilfoil and Curlyleaf Pondweed.
Lakes should have an aquatic plant management plan which includes: ¨ Prevention (We are past prevention, now we need eradication) ¨ Assessment of Problem (This is likely the next step for the Waseca Lakes) ¨ Site Specific Management (Different techniques at various sites) ¨ Evaluate management effectiveness ¨ Monitoring programs (such as secchi disk and phosphorous or nitrogen testing) ¨ Education
The pros and cons on the various types of aquatic plant management were discussed:
Biological (such as the use of grass carp)
Chemical (probably most effective, but not selective)
Mechanical (costly)
Implications for the Waseca Lakes:
Curlyleaf pondweed is the major problem in many southern MN lakes including Clear Lake in Waseca. This is the weed that grows very early in May and June and extends upward to the water surface, then dies out around the 4th of July. It grows so early that in out competes many native plants, then when it dies in mid summer, the nutrients from the decaying plants cause a large algae bloom. If efforts to reduce nutrient flow into our lakes are successful, water clarity will likely increase, but clearer water will also help the curlyleaf pondweed as it will receive more sunlight. So a lake management program for Waseca should include three components; 1. Reduce nutrient flow to improve water clarity and reduce algae growth. 2. Reduce growth of curlyleaf pondweed with various plant management techniques . 3. Encourage native plant growth through re-vegetation programs and with naturally fluctuating water levels.