Before the "hybrid swarm," as it is called, could irreversibly tip the balance of the salt marsh ecosystems, ISP began its tracking and eradication program. Herbicide is selectively sprayed to eliminate hybrids. Initially, it could be sprayed using helicopters, airboats, and tanker trucks with long hoses. Increasingly, backpack sprayers are required to reach isolated or remote stands. The herbicide is only effective during the May to November growing season.