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Techniques and Water Safe Herbicides

Areas around waterways, ponds, and water gardens make ideal locations for weeds to grow.  Not only do these areas have soils loaded with nutrients, but wildlife and flowing water are also constantly bringing new seeds in to establish. The banks of water bodies can also have areas of disturbed, or exposed soil, that allow new seeds to establish quickly and easily.  Managing unwanted vegetation around these areas is not difficult, but special considerations should be made.

It is important to first identify the type of weeds that you want to control. Ideally, these plants should be properly identified, but that can be difficult. Knowing the type of plant will make selecting the right herbicide easy, as well as the best way to apply it.  Plants can be grouped into categories like grasses, broadleaf, and woody species. Recognizing these characteristics can also make herbicide selection easier.

It is also important to consider if there are plants present within the area that does not need to be harmed.  For example, do I want to kill the brush and vines growing around the pond, while not hurting the grasses?  This scenario would be ideal for a selective herbicide.  Selective herbicides are specially formulated to target specific plants while saving others.  However, if your goal is to eliminate everything in the area and start fresh, a broad-spectrum herbicide will best suit your needs.

Herbicides that are used within 10-15 feet of any water body, or if there is a concern for runoff, should be rated for that specific use.  The label included with the product will outline its type of approved uses. For all herbicides, the included label represents federal law and should be followed in its entirety when using that product.

In some cases, the active ingredient in some herbicides may not be safe for use around water.  Other times the type of formulation may not be safe.  For example, the Crossbow herbicide (2,4-D Ester & Triclopyr Ester) is a popular selective herbicide to control brushy areas, consisting of plants like blackberries and Virginia creeper.  This product is an ester-based formulation.  Esters are not safe for use around water.  However, a safe alternative would be Garlon 3a (Triclopyr) and Weedar 64 (2,4-D) which are amine formulations and safe for both around and in water.  Both of these products can be mixed together for the ultimate broadleaf and woody plant control around your pond.

The surfactant used within certain herbicides may also prevent it from being used around water.  A surfactant is a compound premixed, or added, with herbicides to increase the penetration, surface area, and ability of the herbicide to stick to the plant. However, the use of a surfactant is important for use in treating around bodies of water.  A surfactant will help keep the herbicide on the target plants and also help cut through the waxy cuticle, increasing absorption.  Avoid herbicides with premixed surfactants around water.  For example, the commonly used herbicide, Roundup, has a premixed surfactant that can be toxic to aquatic life. A safe alternative would be to use a similar product, Roundup Custom or Rodeo, and mix an aquatic-rated surfactant like Cidekick II.  

When we think of herbicide use, we often think of a foliar application method.  This is the most common method, which includes diluting the herbicide in water and then spraying on the leaves of the target weeds.  This method is very effective in covering large areas, or areas that are below eye level.  However, we should never spray above the head and especially around water.  This reduces injury potential and herbicide drift into unwanted areas.

Oftentimes around water, you will see large shrubs or trees established.  The abundance and nutrient-rich soil and water, allow certain species to thrive and grow quickly.  In these situations, we can use a direct method called “basal bark” that involves treating individual trees and shrubs.  This method requires mixing the herbicide with an oil carrier that allows the herbicide to be absorbed through the bark and into the plant.  This is a very safe method that allows for specific targeting of individual plants and the use of a herbicide that may not be labeled for use around water.  For example, Garlon 4 is very effective on plants like alder, sweetgum, and tree-of-heaven, which are all common around water.

A similar method for the control of large shrubs and trees around water involves the “cut stump” method.  Many woody species have the ability to regrow from the root collar and oftentimes will split into multiple stems or trunks.  Using the cut stump method of herbicide treatment will not only kill the roots but also provide direct herbicide application without risk of entering into adjacent water.

The cut stump method is easy to use.  First, fell the tree or shrub.  Then immediately paint a concentrated herbicide solution directly on the stump.  This must be done within a few minutes of cutting to be the most effective.  The products Habitat, Garlon 3a and Roundup Custom are examples of herbicides that are excellent for the cut stump method and safe for around water.

Nuisance weed control around streams, ponds, and water gardens shouldn’t be something that is feared or avoided. Removing these weeds and establishing healthy grass will not only help prevent future issues but increase accessibility and enjoyment of the area.  An easy reference guide has been included below with aquatic-approved herbicides and common trade names.

Glyphosate

This broad-spectrum herbicide is effective on a variety of plants growing along and in waterways.  Glyphosate is also categorized as a systemic herbicide, which means it will translocate throughout, killing the entire plant.  Glyphosate dissociates in water relatively quickly. This product can be used as a foliar application and cut stump.

Target Plants

Terrestrial (Examples): Grasses, Ragweed, Thistle, Henbit, Sesbania, Wild Mustard, Sandbur, Pennywort, Bamboo.

Aquatic (Examples): Alligator weed, American Lotus, Smartweed, Waterhyacinth, Torpedograss

Common Trade Names

Rodeo, Roundup Custom, AquaNeat, AquaStar

Imazapyr

This is another broad-spectrum herbicide that works in a similar method to glyphosate by preventing the plant from making essential amino acids.  Also a systemic herbicide, imazapyr can be absorbed by the plant’s foliage and root system.  A benefit of this chemical is its soil activity and ability to stay in the soil acting as a preemergent herbicide.  Hardwood trees are extremely sensitive to imazapyr, therefore do not spray underneath desirable trees.  This product can be used as a foliar application, basal bark, and cut stump.

Target Plants

Terrestrial (Examples): Bahia, Fescue, Dogfennel, Pokeweed, Privet, Sweet gum, Tree-of-heaven, Chinese tallow

Aquatic (Examples): Alligator weed, Floating heart, Waterhyacinth, Lemon bacopa, Parrot feather

Common Trade Names

Habitat, Polaris, Arsenal

2,4-D

This herbicide is categorized as a selective herbicide that targets many types of broadleaf plants.  This systemic herbicide can be sprayed over many types of grasses to eliminate weeds, while not impacting the grasses.  2,4-D comes in both an ester and amine formulation, however, the amine formulation is the only one rated for use near or in water.  This product also comes in a granular (Navigate) that can be spread in ponds to combat certain plants growing within the water. This product can be used as a foliar application, basal bark and cut stump.

Target Plants

Terrestrial (Examples): Bitterweed, Carpetweed, Horseweed, Morningglory, Pennywort Purslane, Ragweed, Thistle, Wild onion

Aquatic (Examples): Milfoils, Parrot feather, Smartweed, Watershield, Water lily, Alders, Willows

Common Trade Names

Weedar 64, Navigate, Sculpin G

Triclopyr

This is a selective herbicide that targets broadleaf and woody plants where desirable grasses need to be saved. This product will move throughout the plant-killing both the leaves and roots. Triclopyr is very effective at cleaning up overgrown, brushy areas that have been let go.  Triclopyr comes in both an ester and amine formulation, however, the amine formulation is only one rated for use near or in water.

Target Plants

Terrestrial (Examples): Dandelion, Curly dock, Smartweed, Tropical soda apple, blackberry, gallberry, kudzu, poison ivy, poison oak, sweetgum, sumac

Aquatic (Examples): Alligator weed, Milfoil, Parrot feather, Pennywort, Waterhyacinth, Watershield, Water Primrose

Common Trade Names

Renovate, Garlon 3a, Navitrol, Renovate Max G (Triclopyr and 2,4-D granule)