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Thursday, May 5, 2016

Assess your pond's health

Thursday, April 16, 2009

Vegetation in ponds is important and necessary for a well-balanced pond to maintain habitat and food chain relationships within the pond. Also, key is plant diversity with a large number of different species rather than a large number of a single species of an aquatic plant.

Rooted plants can help stabilize banks that also provide shady areas around the perimeter of the pond. One's goal of aquatic weed control should never be to eliminate aquatic vegetation from a pond, rather to manage excessive growth, particularly from aggressive plant species.

Oxygen levels are influenced by plant growth and death, which can cause fish kills. Plants produce oxygen during the day during photosynthesis and use oxygen both day and night during respiration.

The result is low morning oxygen levels during summer, where fish come to the surface for oxygen. When oxygen levels are this low, a fish kill may be imminent. Even if a fish kill does not occur, fish would be at greater risk to disease and toxicants introduced into their environment. A sudden death of plants in a pond also can rapidly decrease oxygen levels.

The plant death results in fewer plants producing oxygen from photosynthesis. Further compounding the problem is that the decomposing plants respire which uses oxygen that would otherwise be available to fish. While it is difficult to predict plant death from temperature swings, cloudy periods, pond turnover, etc., it is critical that poor pond weed management with improper herbicide timing not be the cause for massive plant death.

Timing is very important when using chemical weed control methods in the pond. Late spring (April-May) is the best time for most methods of chemical control. Plants are small at this time allowing the herbicide to be more effective. Also the smaller plants help to minimize the mass of the resulting decomposing plants that remove oxygen from the water. Also temperature is critical so early treatments may not be effective if the water is too cold. Typically, water temperatures should be in the 60s for best control.

One of the biggest problems that many pond owners have is calculating the size of the pond. It has been my experience that most people over estimate the size of their pond. Since ponds are not square and are naturally asymmetrical, it is easy to overestimate size.

This can result in over applying chemical measures for weed control and kill more plant species than desired. Using aerial photos and a dot matrix, one can more effectively estimate pond size. In Clay County, the digital soil survey in the local SWCD office is a great tool.

One of the most common plant complaints is algae, which many incorrectly refer to as moss. Copper sulfate is an effective control where 2.7 pounds is used per acre foot of water. So if the pond is one acre with an average depth of 10-feet, one would need 27 pounds of product. The best method to distribute copper sulfate is to place the material in a burlap bag and tow the bag behind the boat until the crystals are dissolved.

Do not throw the crystals in the water as this will be ineffective. A good time for copper sulfate application would be the first couple of weeks in May followed with another treatment during the first couple of weeks of June. July and August treatments should be avoided.

Purdue pub WS-21 Aquatic Plant Management is available at the office with color pictures for identification for only $3.50 each. You may contact the local Purdue Extension Office by calling 829-5020 Ext. 14 in Owen County or 448-9041 in Clay County for more information or publication copies regarding this week's column topic or to RSVP for upcoming events.

Please call first to assure items are ready when you arrive and to RSVP for programs.

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