Friday morning I stopped by and looked at some pond weeds that have taken over a small pond. In terms of pond weed control, we generally use herbicides first to get the problem under control. The weed we identified was a submerged weed called, southern naiad, Najas guadalupensis. Leaves are dark green to greenish-purple, ribbon-like, opposite or in a whorl of three, mostly less than 1/2 inch long and 1/8 inch wide.
Is it temperatures too warm to treat? Temperatures are starting to get warm for treating ponds. Because we are not yet in the hottest part of summer, treating small sections of the pond will lessen the effect of oxygen depletion. Below are some specific recommendations from UGA Extension Aquatic Specialist, Dr. Gary Burtle:
Since the pond is heavily infested with this submerged weed, treat ¼ to 1/3 at each herbicide application and waiting 5-7 days before the next treatment. This method reduces the risk of depletion of dissolved oxygen and allows for herbicide application when water temperatures are hot. It is always a good idea to have an emergency aeration plan to use when applying aquatic herbicides.
Since these herbicides have no residual effect, repeat application may be needed or grass carp should be stocked to prolong control of southern naiad. After the initial herbicide burn down, stock 5 to 10 grass carp per surface acre of the infested area. Use triploid grass carp that are about 1 pound or are 14 inches long in order to avoid predation from largemouth bass in the pond.