The Grand River Conservation Authority has closed parts of Snyder's Flats in Woolwich Township.
Areas of the park will be closed to the public while herbicide is used to treat an outbreak of an invasive plant species.
Phragmites is native to Eurasia. It is a fast growing plant that spreads quickly and out-competes native species for water and nutrients.
Toxins released from its roots into the soil hinder the growth of and kill surrounding plants.
It also reduces the habitat available to birds, turtles, amphibians and other reptiles.
The plant was first discovered at Snyder’s Flats in 2013.
Herbicide treatments in 2014 and 2015 eliminated small pockets of the plant, but follow-up treatments are needed on new and larger areas for another few years.
Affected sections of the park will be marked as closed.
Treatments began on Thursday and are expected to be complete by Monday.
