Written by James Burns
Lake weed killer
What is the best lake weed killer? That depends on a lot of things, including the type of weed, the stage at which the weed is discovered, the water and weather conditions, and local laws and ordinances to name a few. Choosing aquatic herbicides can be a little difficult, so we thought we would offer a few general thinking points.
Pond weed types
To determine the type of weed, you should determine if the plant is an algae, a floating plant, a submerged plant, or an emergent plant. Each type could require different aquatic herbicides. If the weed is primarily underwater, it is likely submerged. If the lake weed looks like a lily pad, it is probably floating, if it is growing straight up from the shallows, it is likely an emergent plant. The various types of algae may be more difficult to identify as algae, since some, like skunkweed, also known as musckgrass and chara, bare a striking resemblance to other plant types. Please note that these classes are merely for the purpose of identification, and may not follow strict definitions. A submerged plant may become emergent, and vice versa. There is an excellent tool for lake weed identification called “Aquaplant“, which can help in the identification process, as well as deciding upon treatment options.
The weed should be identified. Discovering the type of weed will help you to identify the weed, and the best aquatic herbicides to use.
Stage of growth
What is the offending plants stage of growth? Youthful weeds are easier to kill than older hardened weeds. This is known as the juvenileity factor, and may effect the amount of chemical, or even the type of chemical to be used as a lake weed killer.
Water conditions
If the water is muddy or turbid, it will have an effect on the lake weed killer. Most aquatic weed killers are designed to be neutralized by soil particles. Muddy water may require the aquatic plant manager to eliminate the source of the turbidity, and “flock” the water to allow the suspended soil particles to drop to the bottom before proceeding with the use of aquatic herbicides or pond weed killer. Under conditions where turbidity cannot be completely controlled, the use of the most desirable chemical may be sidelined in favor of another chemical which works better under such conditions.
Weather conditions
Weather conditions may cause one aquatic herbicide to be less desirable than another. The use of 2-4d on a hot still day may not be wise. The chemical can volatilize under certain circumstances, and end up damaging nearby vegetation. Large quantities of rain may dilute some chemical products, while others may work well under such conditions.
Lake weed killer types
For our purposes, aquatic herbicides fall into 2 categories:
Contact aquatic weed killer
A contact type aquatic weed killer kills only the part of the plant that it comes in contact with. In many cases, this is sufficient, especially if good management practices are used when following up the treatment. See: Lake Weed Prevention Advice for follow up advice.
Systemic aquatic weed killer
A systemic lake weed killer, when properly applied, kills the plant all the way to the root. Systemic aquatic herbicides can be an advantage in some situations, particularly in shallow areas where proper management may be difficult to achieve due to lack of depth. Systemic herbicides tend to have a longer effect on aquatic weeds.
Laws and ordinances
Some aquatic herbicides may have label restrictions which could preclude their use in your situation. Some may be bound by state or local ordinances. It is always best to do your homework, and do it well before using a lake weed killer.
Lake weed control: Prevention
The most important aspect of pond weed control is what you do after using an aquatic weed killer. If conditions are not altered to reduce the amount of sunlight reaching the lake bottom, the lake weed problem will return. This may involve making the water deeper by dredging, raising the water level, or producing algae bloom to tint the water. Learn more about lake weed prevention See: Lake Weed Prevention Advice
