The effective management of submersed aquatic macrophytes depends on understanding their reproductive biology. Potamogeton crispus L. (curlyleaf pondweed, Potamogetonaceae) produces numerous asexual propagules that make traditional management difficult. It has spread to roughly half of the counties in California (USA) from alpine habitats such as Lake Tahoe to the tidally influenced Sacramento-San Joaquin Delta. Studies were conducted from May 2012 till October 2012 at the bench and mesocosm scales in Davis and Sacramento, California, to explore the effects of benthic barrier control measures on the propagules (turions) of Potamogeton crispus. The first study examined the effects of three benthic barrier materials (jute, polyethylene and rubber) on turion sprouting. Jute benthic barrier material allows some light and oxygen through the fabric, while polyethylene allows oxygen, but not light. Rubber barrier material blocks light and oxygen exchange. Turion viability, as determined by sprouting, was then assessed post-treatment. Results showed no significant differences at the bench-scale for the untreated control (100% sprouting, SE=0%), jute (100% sprouting, SE=0%), or polyethylene treatments (96.9%, SE=2.1%) (n=16 for all treatments, α = 0.05). Rubber treatments resulted in 48.4% sprouting (SE= 10.6%; n=16). Results for the mesocosm experiments showed significant differences between the control and the jute and polyethylene treatments (control = 98.4% sprouting, SE= 1.6%; jute = 71.9% sprouting, SE= 4.5%; polyethylene= 70.3% sprouting, SE= 4.7%, n=16 for all treatments). Jute and polyethylene treatments were not significantly different in the mesocosm experiment. The mesocosm experiment with the rubber barrier significantly reduced sprouting (29.7% sprouting, SE= 6.1%; n=16) compared to other treatments. While light had minimal impact on sprouting, anoxia appeared to be the main factor inhibiting sprouting using benthic bottom barriers. Barrier induced anoxic stress combined with herbicides may potentially offer enhanced efficacy. The second study explored enhancement of the impermeable rubber barrier material with dilute acetic acid loaded into cassava starch "pearls". Turions were exposed for two weeks and then assessed for viability via post-treatment sprouting protocol with and without hydrosoil at the bench- and mesocosm-scale. Results for the bench-scale showed that the 20.8 mmol L–1 acetic acid treatment was not significantly different (p=.4231) compared to the untreated control (Tukey HDS; p≤0.05). However, the 41.6 mmol L–1 acetic acid treatment was highly significantly different from the control (p-value < 0.0001) at the bench-scale, but did not completely inhibit sprouting (mean sprouting of 31.25% (SE= 11.97)). Complete inhibition of sprouting turions occurred for both experiments at and above acetic acid concentrations of 83.3 mmol L–1 (SE= 0). Results showed that tapioca starch saturated with acetic acid and combined with impermeable benthic barriers may offer an effective chemical treatment for the control of Potamogeton crispus. The final study examined hot water exposures under the barriers to kill and inhibit sprouting in turions. Heated water circulated under an insulated benthic bottom barrier may potentially offer a simple non-chemical rapid method to target surface propagules on the sediment, subterranean propagules and young plants. Heated water was used to treat P. crispus turions at the bench and mesocosm scales (25°C, 40°C, 50°C, 60°, 70°C and 80°C exposures for 30 to 300 seconds). Heated water exposures inhibited sprouting turions at 50°C and 60°C at the mesocosm and the bench scales, however, did not completely inhibit sprouting for all time exposures except at the bench-scale 60°C treatment for 300 seconds. For 70°C and 80°C treatment exposures, there was a slight difference at the 30 second exposure mark, but at 60 second and beyond, all 70°C and 80°C treatments provided 100% inhibition. The cost to raise the temperature 60°C from ambient water temperature under the contained limited volume under insulated barriers is estimated to be approximately $2 per 9.3 m2 (100 ft2) for 5 minute treatments or $3459 ha-1 ($1400 acre-1).
|Commitee:||Fischer, Albert J., Stroeve, Pieter|
|School:||University of California, Davis|
|Department:||Horticulture and Agronomy|
|School Location:||United States -- California|
|Source:||DAI-B 75/01(E), Dissertation Abstracts International|
|Subjects:||Horticulture, Plant sciences, Water Resource Management|
|Keywords:||Benthic barriers, Integrated pest management, Macrophytes, Pondweed, Potamogeton crispus|
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