(Beyond Pesticides, January 14, 2013) Pennsylvania’s Presque Isle State Park, located on Lake Erie, recently contracted a commercial helicopter to spray herbicides on 170 acres of the park in an attempt to control an overgrowth of phragmites and narrow leaf cattail. This decision to aerial spray herbicides comes after the park has unsuccessfully tried to control these invasive plant species with ground level herbicide spraying since 1994. Presque Isle is the most popular destination along Pennsylvania’s six-mile Lake Erie coastline, and has over four million visitors a year. Presque Isle is home to over 330 types of birds and more than 800 species of native plants, many of which are rare, threatened, or endangered. This aerial herbicide application may have unintended health consequences for both human visitors and endangered animals that call this park their home. The October spraying also raises questions concerning how invasive species problems are framed, leading to unnecessary pesticide use.
Spraying pesticides aerially can lead to a higher rate of pesticide drift compared to ground application. Given that pesticides can drift even when applied from a truck or a handheld applicator, up to 40% of the pesticide is lost to drift during aerial applications. Even when used correctly, aerial pesticide spraying is notorious for drifting off-site, as many pesticides are easily picked up by wind currents. Pesticide labels also often give inadequate information and unenforceable guidelines for applicators to reduce pesticide drift.
The application in Presque Isle State Park is also problematic because the park is on an island in Lake Erie. Lake Erie faces several daunting environmental challenges, such as a dead zone along the bottom of the lake where there is so little oxygen fish can no longer survive. This dead zone is exacerbated by an excess of algae that grows along the lake floor. Algae feed on phosphorus and other nutrients that enter the lake as runoff from lawn fertilizers and sewage overflows. Extra herbicide drift from this aerial application add to the environmental stress already faced by Lake Erie.
The park decided to use aerial application as a method because it views phragmites and narrow leaf cat tail as an invasive species. Invasive species can cause environmental and economic harm, but this potential harm should not give land managers permission to rely on harmful chemicals to deal with these potential problems. However, the concept of what is or isn’t an invasive species is ill-defined. Some plants, such as kudzu, that are now considered invasive were once planted for erosion control by the U.S. Department of Agriculture (USDA). To deal with invasive species safely, it is important to look at the root causes of how these opportunistic plants can flourish in non-native habitats. Some ecologists argue the real drivers of plant “invasions” are frequently man made: climate change, nitrogen eutrophication, increased urbanization, and other land-use changes. Once invasive species enter an area, they often become established. Even with continuous herbicide spraying, it is unlikely that an invasive plant will ever be completely eradicated. The best management strategy for invasive species is not to spray harmful chemicals, but to prevent invasion in the first place or manage ecosystems that are healthier and less susceptible to invasion.
Beyond creating stronger ecosystems and working to prevent invasion, there are successful least-toxic weed management practices that can be used if an invasive species, such as phragmites, has been introduced into an area. Mowing can reduce plant biomass of phragmites and increase sunlight available to native plant species. Mowing should be carried out once per season during late summer/fall when plants are using most of their energy for seed and flower production. Another method is to flood the area in which phragmites are growing with water. A phragmites stand should be cut to its lowest level, and flooding should occur in late summer in order to maintain and promote native vegetation. Water levels must be maintained at a minimum of 1.5 meters taller than the entire stand and levels must be kept at this height for a period lasting at least six weeks.
Phargmites, like many other invasive species, also has alternative food or craft uses. Young phragmites stems, while still green and fleshy, can be dried and pounded into a fine powder, which when moistened are roasted like marshmallows, and the tiny reddish seeds can be ground into flour. Phragmites can also be dried and woven into mats and baskets.
For more information on invasive weeds and lest-toxic weed management please visit our Invasive Weed Management page.
Source: Public Works
All unattributed positions and opinions in this piece are those of Beyond Pesticides