Invasive hydrilla detected for the first time in Michigan, response begins



Hydrilla, considered one of the most invasive aquatic plants in the world, has been detected for the first time in Michigan. The Department of Environment, Great Lakes and Energy confirmed two small populations of the plant in adjacent private ponds in a residential area of ​​Berrien Springs in southwest Michigan.

Hydrilla is characterized by a whorl of serrated leaves, usually five, surrounding a long stem. Illustration by Bruce Carr.

Hydrilla is characterized by serrated leaves, usually five of which are spiraled around a long vapor. Illustration by Bruce Carr.

Small patches of hydrilla (Hydrilla verticillata) were discovered during routine monitoring after treatment of parrot feathers, another invasive plant found in the pond in 2020. Both species are prohibited in Michigan and are illegal to sell, possess, or import. They are invasive into the state, and both are on Michigan’s invasive species watch list due to potential environmental threats.

Hydrilla has several propagation methods and can spread rapidly, compete with native plants, and quickly form dense infestations of a single species. Tubers, turions (buds), and even small plant debris can grow into new plants, so hydrilla can spread into the water or attach itself to ornamental plants sold for water gardens. It becomes very easy.

“It is not clear how either plant ended up in this pond, but it is possible that seeds or debris from the invasive plant were attached to ornamental plants installed in the past few years.” EGLE said aquatic biologist Bill Kuiper. “Genetic analysis of pond sediment core samples and plant material is planned to help determine how long hydrilla has been here and where in the United States it originated.”

EGLE’s immediate response activities include surveys of connected ponds, inlet streams, and the St. Joseph River to ensure we understand the full extent of hydrilla populations. Herbicide treatments targeting hydrilla plants are underway in infested ponds to prevent further tuber production this season. Response plans will focus on preventing the spread of hydrilla beyond its current location, with the long-term goal of eradication.

Why worry?

Hydrilla was introduced to Florida in the 1950s and has spread throughout the Southeast. Another strain, he said, was first detected in Delaware in 1976 and has since spread to several Atlantic states and Great Lakes states.

Hydrilla can grow in both low and high water quality and is found in lakes, rivers, reservoirs, wetlands, ponds, and streams. The plants are usually rooted in sediment up to 25 feet deep and remain submerged, with long leafy stems floating near the surface. Because they compete with native plants, they can quickly fill lakes and ponds and impede recreational access.

Hydrilla can be treated with herbicides, but it is difficult to eradicate because the tubers and turions remain in the sediment for years and the plants can reproduce even from small debris.

I’ll help you too

Early detection of hydrilla provides a better chance for successful control and eradication. Michigan’s invasive species program relies on reports from the public to aid early detection and response efforts.

identify hydrilla

Look for long, slender stems floating near the water’s surface. Check out the following characteristics:

  • The pointed, bright green leaves are about 5/8 inch long and have small teeth at the ends.
  • The leaves grow around the stem, usually in whorls of five, but can have four to eight.
  • Small floating white flowers bloom from late summer to autumn.
  • A small, white to yellowish potato-like tuber attached to the root.

Please be careful about similar products

Note that the long stems of hydrilla may look like native and exotic aquatic plants common in Michigan. Differences are seen in the number of leaves per whorl and whether the leaf margins are smooth or serrated.

  • Native Elodea (Elodea canadensis and Elodea Nuttalli) have three (rarely four) leaves per whorl.
  • The mare’s tail (Hippuris vulgaris) has 6 to 12 leaves per whorl.
  • The leaves of Brazilian Elodea (invasive) are smooth and do not have serrations on the edges.

Report suspected hydrilla

Please report any suspicious aquatic plants as soon as possible. Include a close-up photo and note the location of the detection in your report.

More information about identifying and reporting invasive aquatic plants can be found at

Michigan’s invasive species program is implemented in conjunction with the Michigan Department of Agriculture and Rural Development. Environment, Great Lakes, Energy. and natural resources.

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