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I think I have either milfoil or coontail. How do I tell the difference, and what chemical should I use? | Ponds & Lakes Q&A

Q: I think I have either milfoil or coontail. How do I tell the difference, and what chemical should I use?

Q: I think I have either milfoil or coontail. How do I tell the difference, and what chemical should I use?

Paul – Greenfield, OH

A: Invasive aquatic plants like milfoil and coontail can cause trouble in your pond or lake. Though they provide food and shelter for birds, insects, fish and other pond critters, they can form dense colonies, reducing access to open water, limiting fishing access, and interfering with boating and swimming.

Milfoil and coontail look similar and – thankfully – can be treated with similar chemicals. Here’s what you need to know about identifying and managing these nuisance plants.

Milfoil Identification

When you think milfoil, think feather-like.

Many different species of milfoil and watermilfoil exist in North America. In general, milfoil is found in water that’s less than 20 feet (6 meters) deep. In water less than 15 feet (4½ meters) deep, it can form dense mats over the surface. The plant is comprised of long stems with air canals and flat, feather-like, whorled leaves that are pinnately divided.

Milfoil is an important food source for waterfowl, but these nuisance plants can aggressively invade lakes, ponds and waterways. Once they’re established, they’re almost impossible to eradicate, and so periodic maintenance is necessary to keep them under control.

Coontail Identification

When coontail comes to mind, think of a Christmas tree.

Also known as hornwort, coontail also thrives in water less than 20 feet deep. The rootless invasive plant grows below the surface, and it has a central hollow stem and dark green leaves that are spiny, forked and bushy near the tip, giving it its “coontail” or Christmas tree appearance.

Like milfoil, coontail provides food for waterfowl and cover for young bluegills, perch, largemouth bass and northern pike, but it needs to be managed to prevent it from taking over your pond or lake.

Keeping Them Under Control

Many of the submerged weed chemicals available treat both milfoil and coontail. Depending how you use your pond, the best choices are:

  • Ultra PondWeed Defense®: This liquid herbicide has short-term drinking (three days for human consumption; one day for animal consumption) and irrigation restrictions (five days).
  • Navigate: A granular herbicide, Navigate is great for spot-treating problem areas. It has longer consumption and irrigation restrictions (21 days) than the others.
  • Fluridone (Sonar™): If your entire pond is infested, try Sonar™. It can kill the invaders down to their roots, but expect slower results (it can take up to 90 days for full protection) and longer irrigation restrictions (30 days). Note: Sonar™ should only be used in ponds with little to no flow.
  • Clipper™: To use Clipper™, you’ll need to mix the quick-dissolve granules with water – but you can start using the water again for irrigation in just five days.

Regardless which one you choose, the best time to apply it is when the weeds are actively growing.

Help from the Experts

If you can’t figure out which aquatic weed is growing in your pond, pull one (or more!) from the pond, snap a picture of it and send it to weedid@thepondguy.com or mail us a sample in a dry paper towel. We can help you identify the invader and suggest the best chemical to control it.

Pond Talk: What’s your go-to herbicide to treat invasive aquatic plants?

Broad Spectrum Pondweed Control - Pond Logic® Ultra PondWeed Defense®

What chemical should I use to treat water milfoil? | Ponds & Lakes Q&A

What chemical should I use to treat water milfoil?

Q: What chemical should I use to treat water milfoil?

Douglas – Goddard, KS

A: Before we dive into how to treat this aquatic invader, let’s get to know it a little better first.

Water milfoil, also known as Eurasian Water Milfoil (Myriophyllum spicatum), is a submersed aquatic plant that’s native to Europe, Asia and northern Africa. It has feather-like leaves that grow from white, red or brown stems, and some species produce four-petaled pink or reddish flowers that rise a few inches from the water’s surface.

Eurasian water milfoil thrives on fertile, fine-textured, inorganic sediments. An opportunistic species, the plant prefers water bodies that receive nitrogen and phosphorous-laden runoff, like a farm or agricultural pond. Growth explodes when water temperatures rise, which promote multiple periods of flowing and fragmentation (or when pieces of the plant grow roots and develop new plants).

If left unchecked, water milfoil can dominate a pond or lake in no time.

Controlling Growth

The good news is that you can find myriad products to manage this invasive species. The chemical you choose has to do with several factors.

Closed or open system? If your pond is mostly covered with water milfoil, does not have water flowing in and out, and is not used for irrigation, SePRO Sonar™ A.S. Aquatic Herbicide will be your best choice. The product uses the active ingredient fluridone, which effectively controls a wide range of floating, submerged and emergent aquatic vegetation including duckweed, hydrilla, bladderwort, naiad, elodea, water lily, coontail, pondweed and water milfoil – giving you more herbicide bang for your buck.

Small area or large? If you’re treating a smaller area of a pond or lake, Aquathol® Aquatic Herbicide works like a charm. It’s a rapid-acting contact herbicide that drops aquatic weeds below the water surface in four to seven days, though heavy growth may require a second application in 10 to 12 weeks.

Spray or granular? If you prefer granular herbicides to spray ones and have a smaller area to treat, choose Navigate. This granular herbicide is ideal for spot-treating weeds around docks, beach areas and shorelines, killing the roots of both submerged and floating plants, including water milfoil, coontail and water lilies. You’ll see it go to work within 10 days; you’ll see full effects in three to five weeks.

Plant, Human Considerations

When choosing a chemical herbicide, pay special attention to use restrictions. Some of these products have limitations for use in irrigation ponds, swimming holes and other situations until the chemical has adequately broken down in the water.

Also consider the other critters – plants, fish and animals – that live in your pond. Certain products can harm game fish, koi or goldfish, and can kill off prize water lilies and other welcome aquatic plants.

Pond Talk: How do you manage invasive plants in your pond or lake?

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