APMS Home |
2005 Index |
JAPM Search |
Volume |
43 |
Page |
85 |
Title |
Comparative Response of Two Hydrilla Strains to Fluridone |
Author(s) |
Angela G. Poovey, K.D. Getsinger, and A.B. Stewart |
| Keywords | Hydrilla verticillata, submersed aquatic vegetation, bleaching herbicide, chemical control, b-carotene, herbicide resistance |
| Abstract | Experiments were conducted in a controlled-environmental growth chamber to evaluate the response of two strains of the invasive submersed plant Hydrilla verticillata (L.f.) Royle to fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl)phenyl]-4(1H)-pyridinone). To assess plant injury, shoots were potted and placed in 10-L aquaria, grown to pre-canopy condition, then dosed with 0, 0.5, 5, 50, 500, and 5000 µg L-1 active ingredient (ai) fluridone for a 91-d exposure period. Apical tissues were analyzed for b-carotene pigment concentrations at intervals during the herbicide exposure period. The I50, based on b-carotene concentrations, was 17.9 µg ai L-1 for Strain B and 3.68 µg ai L-1 for Strain A after 7 days. After 30 days, the I50 for Strain B was 47.8 µg ai L-1 and 3.14 µg ai L-1 for Strain A. For a plant biomass study, hydrilla shoots from Strains A and B were potted and placed in 52-L aquaria, grown to pre-canopy condition, then dosed with 0, 0.05, 0.5, 5, 50, 500, and 5000 µg ai L-1 fluridone for a 90-d exposure time. The GR50 for shoot biomass was 37.6 µg ai L-1 for Strain B and 5.78 µg ai L-1 for Strain A. Root biomass was negatively affected by fluridone concentrations, but not by strain. Based on these results, Strain B of hydrilla exhibited symptoms of fluridone resistance. With fluridone resistant hydrilla present in 20 Florida lakes, development of new chemistries with different modes-of-action is needed to establish a management program. |