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Netherland, M.D. and K.D. Getsinger, 1995. Potential Control
of Hydrilla and Eurasian Watermilfoil Under Various Fluridone Half-Life
Scenarios, US Army Corps of Engineers.
Reprinted with from Journal of Aquatic Plant Management
(1995) 33: 36-42
Potential Control of Hydrilla and Eurasian Watermilfoil Under
Various Fluridone Half-Life Scenarios
Abstract
Fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone} efficacy
against Eurasian watermilfoil (Myriophyllum spicatum L.) and hydrilla (Hydrilla
verticillata (L.f.) Royle) was evaluated by simulating herbicide
degradation/dissipation half-lives (t ˝) under controlled-
environment conditions. Fluridone treatment rates of 100 μg/L
for 7,10, and 14 d t ˝, 50 μg/L for 14 and 21 d t ˝,
25 μg/L for a 28 d t ˝, and static treatments of 5 and 15
μg/L for 105 d were tested. Chlorophyll content and net photosynthesis were
measured at 7, 28, 56, 77, and 105 d post treatment, and biomass was collected
at 28, 56, 77 or 84, and 105 or 108 d post treatment to assess efficacy. The 7
and 10 d t ˝ treatments dissipated to 0 μg/L at 42 and 62 d
respectively, resulting in rapid recovery of both hydrilla and Eurasian
watermilfoil. The 14 d t ˝ resulted in exposures of 82 to 84 d, and
although hydrilla biomass remained significantly reduced, physiological recovery
indicated the potential for biomass recovery. Eurasian watermilfoil was
completely controlled at 84 d post treatment following both 14 d t ˝
treatment. The 21 and 28 d t ˝ and static treatments maintained low
fluridone exposures throughout the 105 d study period. These treatments reduced
hydrilla biomass significantly (> 90%), and physiological variables showed no
evidence of recovery at completion of the study. These treatments also resulted
in near 100% control of milfoil biomass by the 84 d harvest. Results indicate
that following initial injury at higher treatment levels, extremely low levels
of fluridone (1 to 3μg/L) prevent recovery. Herbicidal activity of these
low concentrations may explain the long-term control achieved with fluridone in
situations that allow long degradation half-lives (>14-d).
Entire Paper
Contact: Kurt Getsinger, US Army Corps of Engineers, Waterways Experiment
Station, 3909 Halls Ferry Road, Vicksburg, MS 39180
Key Words: Hydrilla, Eurasian_watermilfoil,
Chemical_control
Product Type: Research, Control
User Type: Resource Management
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