03-31-2010, 02:10 PM
The Department of Natural Resources' access site on Lake Manitou will be available through the last weekend of April but will close temporarily for an unspecified length of time as soon as April 26.
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. Two years ago the DNR relaxed access restrictions at the lake, expecting to have to eventually re-close the area due to the persistent nature of the plant. Last year the DNR ramp closed April 27 and opened July 1.
"No one should interpret these two closings 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 last year, and that was confirmed in surveys last fall.
"As a result of three years of controls, we have decreased the tuber population 95 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, just as last year. To determine if doing so is advisable, the DNR will conduct a plant survey 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 June's plant survey, the DNR will maintain chemical concentration up to 5 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.
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.
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. Two years ago the DNR relaxed access restrictions at the lake, expecting to have to eventually re-close the area due to the persistent nature of the plant. Last year the DNR ramp closed April 27 and opened July 1.
"No one should interpret these two closings 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 last year, and that was confirmed in surveys last fall.
"As a result of three years of controls, we have decreased the tuber population 95 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, just as last year. To determine if doing so is advisable, the DNR will conduct a plant survey 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 June's plant survey, the DNR will maintain chemical concentration up to 5 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.
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.