Cattails are an emergent weed that is rooted in the bottom of the lagoon in the soil. They grow best in shallow water, up to three feet deep, like is typically found in a sewage lagoon. Cattails are a tall plant with narrow upright leaves and a brown "sausage" looking seed spike. They are found abundantly in ditches and ponds throughout Missouri.
Mechanical control involves physically removing the cattails. This can be done by cutting the cattails. Cutting when the heads are formed but still immature and a second cutting a few weeks later will give considerable control. Control is best achieved by cutting the cattails 2-3" below the surface of the water, this allows water to enter the breathing tube, killing the plant.
Muskrats will eliminate cattails from a pond, but are undesirable because of the damage that they will do to the berms of the lagoon.
A thick infestation of cattails may need to be removed with a backhoe or trackhoe. This method will get rid of the roots, from which new plants emerge. The disadvantage to this method are that the berms can be damaged from the equipment, the cattails must be disposed of and the cost of hiring the work done.
The Health Department should be notified when a lagoon is being cleaned out. A permit will not be required, but the staff will look at the lagoon before and after cleaning to ensure that no structural work was done to the lagoon.
Burning will get rid of dead litter, but will do nothing to control the growth of the cattails.
Glyphosate (Rodeo) is a systemic herbicide that works from the point of contact, into the vascular system and into the roots. Good contact with the leaves is essential for the herbicide to be absorbed. A nonionic surfactant is mixed with the herbicide to break down the waxy coating on the leaves and provide better penetration. Apply 41/2 to 6 pints per acre or in a 3/4 % solution with hand held equipment. A nonionic surfactant labeled for use with herbicides should be added at a rate of 2 quarts per 100 gallons of spray solution. Apply when plants are actively growing and are at or beyond the early-to-full bloom stage of growth. Best results are achieved during the summer or fall months when the vascular flow is downward into the rhizome. This chemical moves through the plant from the point of contact into the root system. It is essential to get the chemical on each plant. Visible effects usually occur within 2--7 days. Retreatment will only be effective if the plant is still visibly healthy, within 7 days of initial treatment.