LAKE OKEECHOBEE – Airboats will be used to spray herbicide to control torpedo grass, according to Alyssa Jordon of the Florida Fish and Wildlife Conservation Commission (FWC).

Torpedograss, an invasive exotic wetland species, is choking out portions of the northwest marsh of Lake Okeechobee, outcompeting native wetland plant species, and limiting fish and wildlife usage, she explained. Torpedograss, when allowed to grow unchecked, does not allow native marsh species to proliferate because it becomes an extremely dense monoculture. The small amount of beneficial vegetation observed in these areas are not readily accessible to fish and wildlife and, for many species, is not accessible at all.

In March 2019, prescribed fires conducted by the Florida Fish and Wildlife Conservation (FWC) and the South Florida Water Management District (SFWMD) burned an estimated 3,000-5,000 acres of the interior northwest marsh between Pearce Canal and Indian Prairie canal, including at least 1,500 acres of torpedograss. In Spring 2019 and 2020, an agricultural boom/spreader truck was used to broadcastapply herbicide (application of a herbicide solution “uniformly over the entire treated area”) to a combined acreage of around 1,500 acres of torpedograss, including a portion of the area burned. The torpedograss was estimated to be about 90-100% of the species present. Monitoring in April 2020 showed 25-50% re-growth of torpedograss throughout the management area. The areas that had regrown from the 2019 management were re-treated in Spring 2020, with additional new acres added on to the management area. Monitoring will occur in April 2021, but surveys have shown only about 10-15% re-growth of torpedograss in the management area, an improvement from the year before, according to Jordan.

To treat the exotic invasive torpedograss, Airboats will be used to manage torpedograss located in the Northwest Marsh of Lake Okeechobee by “directed application” (also known as “spot treatment”). Although no other vegetation species will be targeted, small amounts of other species may be affected by the herbicide when growing within the managed torpedograss, according to Jordan.

Imazapyr, labeled and approved for aquatic use by the U.S. Environmental Protection Agency (EPA) and the Florida Department of Agriculture and Consumer Services (FDACS), will be applied at the recommended label rate of 64 oz/acre.

The management site is located approximately two miles from the Herbert Hoover Dike. Access to the treatment site will be via airboats mobilizing from Okee-Tantie airboat ramp, Yankee Point and Indian Prairie boat ramps to minimize public interaction. If the lake gets too low for airboats, access will be with swamp buggies from the Herbert Hoover Dike.

Up to 200 acres of torpedo grass within a 1,500-acre area will be managed. Additional management may be conducted as dictated by need if time and funding allow.

Jordan explained that over the past two years, broadcast management has occurred over approximately 1,500 acres. This past year, many native species, such as spikerush, bulrush, cattail, pickerelweed, duck potato, smartweed and marsh lilies, have been found within the management area in areas previously dominated by torpedograss. Waterfowl have been seen utilizing this area. Wading birds have also been observed throughout the area, and will likely increase in numbers as the lake becomes shallower throughout the spring. Snail kites have also been seen foraging in this newly-opened area and a variety of fish have also been seen throughout the area. When the lake was drier in spring 2020, prolific wildflower blooms were observed.