Plant Management in Florida Waters

Hydrilla

Scientific name: Hydrilla verticillata
Origin: Southeast Asia
Introduction: Early 1950s, aquarium trade
Aquatic community: Submersed, surface mats
Habitat: Inches to >30 feet deep
Distribution: Statewide
Management effort: Eradicate new infestations Maintenance control of established plants
2020 Acres Treated: 16,100

Hydrilla

Stems can elongate as much as 6-8 inches per day in Florida’s peak growing season
Can cover entire water body surface 1-2 years after introduction
80% of plant mass is in the upper two feet of water column
- blocks sunlight and shades out native plants
- blocks air exchange and consumes oxygen, leading to fish kills
- blocks access, navigation, and recreation
- breaks loose and jams against bridges and dams
Reduces recreation-based incomes and property values
Doubles sedimentation rate from senescing leaves and stems
Disperses by fragments, buds, and runners (does not produce seeds)
Resists long-term control via underground propagules (tubers)
- millions produced per acre
- no effective tuber control method
- viable tubers lie dormant for as long as seven years

Biological: Sterile grass carp stocked in about 100 public lakes; 4 host-specific insect species released with few successes; FWC is not currently funding overseas exploration for additional host-specific insects
Chemical: Large-scale: potassium endothall, diquat, bispyribac, fluridone, penoxsulam; topramezone – small-scale: copper, diquat – research is focusing on combinations of herbicides, especially contact type herbicides with systemics
Mechanical: Harvest from spring runs and boat trails in deep water, harvest or shred mats lodged against structures (bridges, dams)
Physical: Hand pull / diver dredge new infestations, or in fast-flowing water