Alternative Algae Control 06

Evaluation of Alternative Methods for Managing Algae in California - 2006
Project Leader and Principal Investigators David Spencer, ecologist, USDA/ARS, Exotic and Invasive Weeds Research Unit, Dept. of Plant Sciences, UC Davis	Research on control of filamentous algae in California rice fields broadened considerably in 2006. Studies examined copper, zinc, phosphorous, herbicides, and several experimental products. Microbial products Two microbial products – EM-1 and EM-5 – did not reduce algal growth relative to untreated controls at several different concentrations. In fact, one treatment actually stimulated algal growth with one of the products. Herbicides Experiments with new ALS-inhibiting herbicides – bispyribac, imazamox and penoxsulam – did not show consistent reduction in algal growth. Carfentrazone reduced algal growth, but at rates that could produce injury to rice. Flumioxazin also reduced algal growth; however, this product is used in peanuts and its potential impact to rice is unknown. Zinc examined Zinc reduced algae at 20 ppm, a rate equivalent to 50 pounds/acre. Zinc reduces chlorophyll in algae cells and was detectable within 48 hours of treatment in experiments. Zinc at 20 ppm was more effective than a standard copper treatment at 1 ppm. In another experiment, algae were reduced by 50 percent with commercially available liquid zinc sulfate solution. This may partially explain anecdotal reports that fields with zinc sulfate added at 50 pounds/acre (i.e. 20ppm) as a fertilizer, often have less severe algae problems. Phosphorous management One study found that burying fertilizer phosphorous greatly reduced algal growth. Results of experiments with soils collected from five separate rice fields indicate that burying phosphorous fertilizer at an inch deep in the soil reduces the level of phosphorous in the overlying water to levels similar to soils that received no additional phosphorous. Copper and Straw The presence of rice straw affects the ability of copper compounds to kill algae. Experiments with combinations of copper sulfate or Cutrine Ultra found that rice straw reduces the toxic properties of copper up to 8 ppm. The straw binds copper ions up to that point, thus reducing its effectiveness in algae control. Barley Straw Another study examined whether commercially available barley straw wattles could be used to control algae. An experiment conducted in an active rice field found that algae were not reduced with barley straw – even though water temperatures in the field were warm enough to ensure straw decomposition and release of algaecides.

Evaluation of Alternative
Methods for Managing
Algae in California - 2006

Project Leader and Principal Investigators

David Spencer, ecologist, USDA/ARS, Exotic and Invasive Weeds Research Unit, Dept. of Plant Sciences, UC Davis

Research on control of filamentous algae in California rice fields broadened considerably in 2006. Studies examined copper, zinc, phosphorous, herbicides, and several experimental products.

Microbial products

Two microbial products – EM-1 and EM-5 – did not reduce algal growth relative to untreated controls at several different concentrations. In fact, one treatment actually stimulated algal growth with one of the products.

Herbicides

Experiments with new ALS-inhibiting herbicides – bispyribac, imazamox and penoxsulam – did not show consistent reduction in algal growth. Carfentrazone reduced algal growth, but at rates that could produce injury to rice. Flumioxazin also reduced algal growth; however, this product is used in peanuts and its potential impact to rice is unknown.

Zinc examined

Zinc reduced algae at 20 ppm, a rate equivalent to 50 pounds/acre. Zinc reduces chlorophyll in algae cells and was detectable within 48 hours of treatment in experiments. Zinc at 20 ppm was more effective than a standard copper treatment at 1 ppm.

In another experiment, algae were reduced by 50 percent with commercially available liquid zinc sulfate solution. This may partially explain anecdotal reports that fields with zinc sulfate added at 50 pounds/acre (i.e. 20ppm) as a fertilizer, often have less severe algae problems.

Phosphorous management

One study found that burying fertilizer phosphorous greatly reduced algal growth. Results of experiments with soils collected from five separate rice fields indicate that burying phosphorous fertilizer at an inch deep in the soil reduces the level of phosphorous in the overlying water to levels similar to soils that received no additional phosphorous.

Copper and Straw

The presence of rice straw affects the ability of copper compounds to kill algae. Experiments with combinations of copper sulfate or Cutrine Ultra found that rice straw reduces the toxic properties of copper up to 8 ppm. The straw binds copper ions up to that point, thus reducing its effectiveness in algae control.

Barley Straw

Another study examined whether commercially available barley straw wattles could be used to control algae. An experiment conducted in an active rice field found that algae were not reduced with barley straw – even though water temperatures in the field were warm enough to ensure straw decomposition and release of algaecides.