Lake Problems? We Have Solutions!

Lakes are a very important part of life in Texas, in fact they may be the most important part of our physical existence here in the Lone Star State. Why do I say this? They provide the water for fishing, and other recreational activities, but most of all, they provide one of our main sources of water for fueling industry, personal hygiene, and drinking water. Aside from Caddo Lake, (which now has a very serious Giant Salvinia problem) there are no other naturally occurring lakes in Texas. We have them as a result of sheer willpower, and good long term planning! They are one of our most necessary resources, and as such, deserve our highest level of attention.

Problems With Lakes:

Probably the best known most controversial problem in Texas lakes is Hydrilla Verticillata, a non native aquatic plant from the East. It has taken over many ponds and lakes, and is becoming a larger problem every year, but it is certainly not the only vegetative pest to present problems in Texas waters. Nor is it the only non native pest in our lakes. Eurasian water milfoil, from, as the name suggests, Europe and Asia (also Africa), is also causing problems, and we have a vast number of other non native and native lake and pond weeds, good and bad, inhabiting our waters.

Ponds and lakes need vegetation.

Some vegetation in lakes and ponds is a good thing. Vegetation is a part of the life cycle, but you can get too much of a good thing. I have heard some fishermen say that a little hydrilla is a good cover for bass. While this may be true, there is rarely such thing as "a little" hydrilla. It wants to, and will, if left unchecked, take over the entire body of water. I have run across stands so thick, that it made rowing almost impossible.

Catch it early!

The cost of treating such lake weeds as coontail, hydrilla, watermillfoil, salvinia, duckweed, or waterhyacinth may seem expensive, and it can be. The chemical cost is a large part of the equation. For that reason, gaining control in the early stages is of the utmost importance. Hesitation can be expensive!

The following information is from my observations on a private lake in East Texas:

This lake has a wide variety of aquatic plant life, some beneficial, and some "Non Native" invasive plants. The biggest problem is the hydrilla, which we can bring under control with endothal, a contact herbicide. The problem will recur, and there are some options.

1. Continued periodic treatments as necessary. The need for these can be lessened by spot treatments as needed, by the use of shading dyes to slow chlorophyll production, and vegetative nutrient barriers at the inlet, to help slow the ag nutrients flowing into the lake from off site.

2. The Use of mechanical harvesting, which is the least practical, and least desirable course, since hydrilla has a 50% replanting rate due to it's ability to reproduce vegetatively. 

3. Introduction of triploid grass carp. If this is desired, we will have to make application with the Parks and Wildlife Department's Inland Fisheries Division, and arrange to buy the fish. There are potential problems with this course of action. The carp are sterile, but escape downstream is a parks department concern, also, the fish prefer hydrilla to other aquatic plants, but will eat many other types of vegetation, so that removal of desirable vegetation can be a concern.

The first is the least complicated, and will fit well in a good IPM management plan,  and does not preclude the use of the others at some point if this should become desirable.

What I recommend, is that after finishing the initial treatment, we monitor the situation closely for regrowth. Small areas can be spot treated, and over time, this will lessen the effects of it's presence, and the cost of maintaining it. The most important aspect, is monitoring, and quick response. Once the hydrilla is established as it is in this case, it is almost always a continuing problem, but can be managed. 

What makes Hydrilla so difficult?

1. It can reproduce vegetatively, so after being disturbed, it may transplant itself. This means that if it is broken into a thousand pieces, 500 new plants may result. 

2. It has tubers, which can live in a state of dormancy for 4 years or more.

3. It has large quantities of seed, which can obviously be replanted, although we don't know a lot about seed viability. 

4. Areas of the plant, can readily reproduce new adventitious plants in a short time.

5. It has few naturally occurring predators in East Texas.

6. It has an astonishing  growth rate.

Treatment Issues:

One of the problems we have when treating aquatic vegetation, is "fish die back". This problem is almost always caused by oxygen depletion, which is the result of dying and rotting vegetation, and not from the chemical itself. This can be prevented by treating no more than one half of the area at a time, and allowing sufficient time between treatments for the complete decay of the plant material.

What to do if you find hydrilla in your pond or private lake:

First, don't panic. It is not the end of the world. Early detection is an important first step. Next, make sure it is hydrilla, and not "coons tail" or some other weed. One of the main identifying features of hydrilla for me is the serrated edges, and the spine on the bottom side of the leaf whorl. If you have trouble identifying it, find someone who can. Don't take it to them, have them come to you since it is in the TPW prohibited exotic species list, and is therefore illegal to transport.

Texas Parks and Wildlife would like for people to report the presence of hydrilla in private ponds and lakes. This information could be helpful to them in several ways, particularly in tracking the spread of the problem. These days, it is most often spread by sprigs stuck in boat propellers, or in live wells, but can also be spread by the movement of water from an infested pond to another downstream.

You have several treatment options at your disposal. I will list them as:

MECHANICAL: The actual physical removal of the plants. The plants have tuber type roots in the soil, and any of these left over can remain viable for several years. Broken stems from the plant can grow new plants at a very high rate, so if you break it into 100 pieces, it is likely that you will have fifty or so new plants. Aquatic lake and pond weed mechanical harvest is a last resort, to be used  only when the owner is resigned to the idea of doing it forever.

BIOLOGICAL: At present, the only truly viable biological control, is the triploid grass carp. These are voracious eaters of hydrilla, but in a high concentration, they can also do away with a lot of vegetation that the pond or lake may need to stay healthy, thus eliminating food and cover for other fish. They rarely make much progress in the first year, and there is the risk of escape. They are sterile, but can eat a lot of vegetation in any new environment where they might find themselves. If this option is considered, you will need a permit from the TPW inland fisheries division and a barrier to prevent their escape.

CHEMICAL: Most of the chemicals used to control hydrilla, are some of the safest herbicides ever developed. In many cases this is the best overall choice. These chemicals, work rapidly, and degrade quickly. One thing to keep in mind, is that if you use your pond or lake for irrigation, you might want to make plans to avoid irrigating for a few days after treatment. Be sure to read and follow the label directions before making an application with any chemical. In some small bodies of water, the use of dyes for shading may be advantageous.

Other Options: There are other options, such as lowering the water level and then performing mechanical and chemical controls. In most cases this seems impractical. Most vegetation gets its start in shallow water, where sunlight penetrates to the bottom. If your lake level can be raised, that might help. If you can dredge the edge of the pond to increase the depth of the edges, this can help as well.

 Copyright 2007 James Burns

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