MDC says non-native Alligatorweed found at Otter Slough Conservation Area near Dexter

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CAPE GIRARDEAU, Mo. – Immediate steps are being taken by the Missouri Department of Conservation (MDC) to eradicate an invasive, non-native aquatic plant known as Alligatorweed recently discovered at Otter Slough Conservation Area (CA). If not eliminated, this fast-growing plant could suppress desirable native wetland plants, negatively impacting wildlife and fisheries habitat.

Invasive plants are aggressive, non-native species whose presence causes or is likely to cause economic harm, environmental harm, or harm to human health.

Mike Reed, MDC Fisheries Management Biologist said the plant – native to South America – grows quickly, forming dense mats that crowd out native species. These invasive plants grow in or along streams, ponds, lakes, ditches, and wetlands.

This is the first time the plant has been recorded in Missouri although it is found in several southern states. “We believe the plant was introduced inadvertently by boat, motor, or trailers of waterfowl hunters who had been in southern states such as Arkansas or Louisiana, which have a lot of this plant,” Reed said. “The plant spreads by stem fragments very readily.”

He said this invasive plant can dramatically reduce habitat for wildlife and fish, interfere with boating and recreational use, and even make flooding worse.

A treatment plan has been implemented by MDC to combat this issue, Reed said, including eradicating the plant from Unit 31 at Otter Slough and preventing it from colonizing additional units at the conservation area.

“Unfortunately, Unit 31 at Otter Slough CA is being held out of the waterfowl hunting program this fall to allow the unit to be held dry in attempt to kill remaining alligator weed,” he said.  

Reed said the plant is controlled successfully in southern states using EPA-approved aquatic herbicides and biological control using a beetle specific to the plant. Herbicide has been used on the Otter Slough alligator weed population, Reed said. But unfortunately, the beetle can’t be utilized as it will not survive Missouri’s winters.

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