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Watch For It---Useful Tips
Don't miss our special segments giving you useful tid-bits of information to help you get the most enjoyment possible from you pond/lake.
Aquatic Vegetation Control
Most aquatic vegetation problems are the result of elevated levels of nutrients, primarily nitrogen and phosphorous, in the pond/lake's water and sediments. These nutrients are always present in some amounts and naturally build up over time. However, man made sources are usually the cause of most problems. These sources include sewage lagoons, septic systems and runoff from pastures and fertilized lawns. It is always best to first identify then reduce or eliminate nutrient source to manage aquatic plants. All other types of treatment are simply treating the symptom and not the underlying cause of the problem.
Aquatic plants should be managed, not eradicated. Aquatic plants are a natural and important part of the pond/lake's ecosystem. They provide important benefits in terms of water quality, food production and fish growth. Aquatic plants also help prevent erosion and adds a majestic effect. Wildlife benefits from the presence of vegetation. To provide the best fishing, we usually recommend that up to 10-20% of the lake bottom be covered with aquatic plants . When the plants exceed this amount, or interfere with other recreational activities and present a nuisance, then management techniques may be required.
Grass Carp
Grass carp are not a cure-all for aquatic vegetation problems. These fish are sometimes selective in the types of vegetation they prefer. There is no way to target grass carp to eliminate vegetation in a particular area such as a boat ramp or swimming area. The entire lake must be "treated". The biggest draw back to the use of grass carp is the result of their tendency to pursue flowing water. The grass carp is a river fish. If it senses flowing water (at the spill way) it will be attracted to it. In ponds/lakes that have significant flows over the spillway (even if only once every year or two), it is extremely difficult to keep the fish in the lake. Proper screening will help. The number of grass carp to stock is based on the weed infestation
problem. Refer to the section titled "Grass Carp" for these recommended numbers and other useful information. We sell two sizes of grass carp, 5-8" and 9-12", for stocking into ponds/lakes with large sized bass populations. Larger sized grass carp are available if bass are trophy size and you're concerned about their survival.
Winter Draw Down
A draw down that exposes plants and portions of the lake bottom to sub-freezing temperatures for a week or longer during the winter can help to control certain aquatic plants. This technique is not guaranteed to work because a warmer-than-normal winter may not provide the hard freeze necessary. If a winter draw down is feasible, I recommend the draw down be maintained from November to March 1. Down stream flooding and negative impacts on fish populations (and fishing) are common negative effects of draw downs.
Mechanical
Because it is labor intensive, the use of mechanical controls is usually only feasible for smaller sized ponds or for spot treatments of smaller areas in larger bodies of water. Various methods include cutting or pulling out the vegetation, raking and/or seining floating vegetation blown into corners by the wind or wave action.
Herbicides
There are many herbicides registered by the Environmental Protection Agency (EPA) for aquatic use. Aquatic herbicides vary in their weed control spectrum. After the weed has been correctly identified, contact a knowledgeable sales representative to select an appropriate herbicide. If you're treating a fishing pond/lake, the herbicide selected must be labeled for food fish use. Most aquatic herbicides have water restrictions that may prevent their use on a particular body of water. Secondary water uses (I.E.: swimming, livestock watering, irrigation, etc.) must be considered prior to herbicide selection and application.
I can not over emphasis "Read the label and follow instructions when using chemical herbicides". The old cliché "that if a little works, more is better", DOES NOT APPLY HERE!!!
Most aquatic weeds begin growth in the early
Spring months when water temperatures are 55 to 60 degrees F. The
Spring months (March, April, May), when water temperatures are between 70 and 80 degrees F., are an ideal time to apply herbicides to control aquatic weeds. At this time of the year weeds are small and are easier to control than during the hot summer months. Aquatic herbicides are not toxic to fish when applied according to label directions Aquatic weeds that are killed by the herbicide undergo decomposition. The decomposition process consumes oxygen and can reduce the amount of oxygen available. If the oxygen level drops below the necessary level, fish kills due to oxygen depletion can occur. Treating only portions of the pond/lake will minimize
the risk of oxygen depletion problems due to weed decomposition. Fish should be observed for 1 week after treatment. Emergency aeration equipment should be available if oxygen
depletion problems occur. Treating the pond with herbicides during the hot summer months is risky. Oxygen levels tend to be lower at this time and weed
bloom levels tend to be higher. Treating only 1/4 to 1/3 of the total surface acreage of the pond/lake at one time will minimize the risk of herbicide-induced oxygen depletion problems. However, in ponds with very low oxygen levels, even partial pond treatments with herbicides may be risky during the hot summer months.
Copper sulfate
Copper sulfate is primarily used to control algae. It is a contact herbicide and quickly kills sensitive algal species. Copper can interfere with gill function and if improperly used can be toxic to fish. The majority of fish kills due to copper sulfate treatments are primarily caused by a massive algae kill and subsequent oxygen depletion problems.
The effectiveness and safety of copper sulfate is determined by alkalinity and water temperature. In water with an alkalinity less than 50 ppm, the rate of copper sulfate needed to control algae can be toxic to fish. Treatment at water alkalinity of less than 20 ppm is extremely risky. In high alkalinity, over 250 ppm, copper sulfate quickly precipitates out and is not effective for algae control. The toxicity of copper sulfate to fish increases as water temperatures increases. Avoid copper sulfate applications during hot summer months.
The drawbacks associated when using herbicides for aquatic vegetation control are:
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Most are very expensive to use.
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Many breakdown or disappear in the pond/lake after a short period of time.
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Re-treatment may be necessary to obtain desired results.
- As with other methods, certain herbicides are suited to whole lake treatments and others as spot treatments of problem areas.
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