This article originally ran in the Ruston Daily Leader on August, 30, 2011.

I have been receiving lots of phone calls recently about controlling weeds in ponds. The easiest way to control weeds in a pond starts with  pond construction. But since it’s too late to discuss pond construction when I get these calls, it usually puts us on the defensive to get control of the weed problem. Also, people tend to wait and call when the pond is completely covered with weeds instead of calling when they first emerge. So for those of you thinking of building a new pond come in and see me before you start and get some of the information that you need to construct a pond as best as possible. But, for those of you that already have ponds, let’s talk about aquatic weeds.

First of all,  just because a plant is in the water doesn’t make it a weed. An aquatic weed is a plant that begins to interfere with the intended use of the pond. Remember some plants are good for ponds. Actually a microscopic plant called phytoplankton gives a pond its greenish tint, helps reduce penetration of sunlight to discourage weed growth and also supplies food for aquatic life.

In order to control pond weeds properly we need to know what the weed is. This is usually difficult to do over the phone and can be very costly if misidentified so I usually prefer to go and look at the pond first hand before making any recommendations.. There are two main control methods that I usually recommend. Which method is used depends not only on the type of weed but also on how much of it there is and the environment surrounding the pond.

The quickest method to use involves chemical controls. There aren’t many herbicides that are labeled for pond use and some are for restricted use, which means you must have a restricted use pesticide license in order to purchase them. Another problem that is of concern is chemically treating a pond with la arge populations of weeds. If you apply the pesticide over the entire pond and you kill a large amount of weeds at one time, those weeds all sink to the bottom and decay. During the decay process oxygen from the water is used. Too many decaying weeds using up the pond's oxygen can cause a fish kill and we don’t want that to happen.

The easiest way to control most of the pond weeds that we have in the area is by stocking your pond with triploid grass carp. In order to purchase grass carp you must receive a permit from The Louisiana Department of Wildlife and Fisheries. The number of grass carp that should be stocked depends on the type of weeds, condition of the ponds and severity of the weed problem. Triploid grass carp prefer submerged plants, but some emergent plants are also controlled.

That pond is meant for recreation. Your enjoyment can be completely ruined by allowing these weeds to get out of control. So if you feel you need some help in identifying your ponds needs please contact me , Gary Stockton, or your parish Extension Service office.