Indiana Department of Natural Resources
402 W. Washington St. W255 B
Indianapolis, IN 46204-2748
Phone: (317) 232-4200
For immediate release: April 8, 2009
Manitou ramp to close temporarily late this month
Reopening depends on status of invasive plant
The Department of Natural Resources' access site on Lake Manitou will be available through the last weekend of this month but will close temporarily for an unspecified length of time as soon as April 27.
All other public and private access sites remain closed, including the city boat ramp on the northwest corner of the lake.
The closure will allow for further treatment of hydrilla, an exotic, highly invasive plant that was first confirmed as being in the lake in August 2006. Last year, when the DNR relaxed access restrictions at the lake, it expected to have to re-close the area again due to the nature of the plant.
"No one should interpret this as a setback in the effort to eradicate hydrilla from Manitou," said Doug Keller, aquatic invasive species specialist with the DNR Division of Fish and Wildlife. "We suspected that hydrilla tubers (similar to roots) remained in the lake when access restrictions were relaxed at the end of June 2008, and that was confirmed in surveys last fall. As a result of two years of controls, we have decreased the tuber population 93 percent and through continued efforts we will eliminate this plant."
The closure will give DNR time to apply Sonar, a chemical that eliminates hydrilla plants, before boats are allowed to come and go. That treatment is expected to be done in mid-May, by which time many of the tubers should have sprouted and emerged through the sediment, making them susceptible to Sonar. Keller said it's likely that periodic interruptions in the availability of the Manitou access site will continue in future years.
"As long as we know that hydrilla tubers remain in the sediments of Lake Manitou, we will implement periodic access restrictions during periods when there is a risk of movement of the plant," Keller said.
It's possible, but by no means a given, that the ramp will re-open at the end of June.
A plant survey will take place in mid-June. If no viable hydrilla plants are found, the DNR ramp will open before the July 4 holiday. If viable hydrilla plants are found, opening of the ramp will be delayed until later surveys reveal no live hydrilla plants.
No matter what the outcome of the June 2009 plant survey, the DNR will maintain chemical concentration between 3 and 6 parts per billion of Sonar through at least the middle of October.
"Hydrilla tubers can sprout at any time water temperature is 55 F or warmer, which requires that a concentration that is lethal to the plant be maintained throughout its growing season to eliminate newly sprouted plants," Keller said.
Sonar, with the active ingredient Fluridone, is an aquatic herbicide produced by SePRO Corporation of Carmel. Humans, fish and other aquatic life are not harmed by Sonar, especially at the extremely low rate being used at the lake, according to Keller.
If and when the risk of hydrilla movement is again low, the DNR will announce that the DNR ramp is again available for use and reopen it.
If and when that happens, the threat of spreading the plant to other waters will still exist. Signs will be placed at the DNR site to remind boaters to self-inspect their watercraft, motor and trailer for signs of plants when taking them from the water. All plant material should be removed and disposed of at the ramp before the boat is towed. Mud should be rinsed from the boat and trailer before transport, since hydrilla tubers could be present.
Boating equipment should dry for five days before being used in another body of water. These precautions should be performed not only at Lake Manitou but also at all waters, to prevent the spread of a host of aquatic invasive species, not just hydrilla.
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Media Contact: Marty Benson, DNR assistant director of communications, (317) 233-3853; cell (317) 696-9812. Doug Keller, DNR aquatic invasive species coordinator (317) 234-3883.
