Insecticide choice for alfalfa may protect water quality
AuthorsRachael Freeman Long
Daniel H. Putnam
Authors AffiliationsR. Freeman Long is UC Cooperative Extension (UCCE) Farm Advisor, Yolo County; M. Nett is owner, Water Quality Consulting, Colorado Springs, Colo. (formerly Walnut Creek, Calif.);; D.H. Putnam is UCCE Specialist in Alfalfa and Forages, UC Davis; G. Shan is Research Scientist Dow Agroscicnces, Indianapolis (formerly Dept. of Entomology, UC Davis); J. Schmierer is Farm Advisor, Colusa County; B. Reed is Farm Advisor, Glenn County.
Hilgardia 56(5):163-169. DOI:10.3733/ca.v056n05p163. September 2002.
Some insecticides used for controlling Egyptian alfalfa weevil have been detected in California's surface waters and are of concern, due to their impact on water quality and toxicity to some aquatic life. To assess the impact of insecticide choice on water quality, we collected tail-water samples from on-farm alfalfa sites in the northern Sacramento Valley over a 3-year period. Samples were collected during irrigation after organophosphate and pyrethroid sprays were applied. We found significant differences between insecticide classes in the mortality of Ceriodaphnia dubia (water flea), a test organism used to detect pesticides in water. Nearly all sites where organophosphate insecticides were used resulted in 100% water flea mortality in a 24-hour test of tail-water samples; pyrethroid-treated sections of the same fields exhibited insignificant flea mortality. The pyrethroids we used provided significantly better control of Egyptian alfalfa weevil than the organophosphates, with no significant differences in beneficial insect counts. Although water runoff does not always occur in alfalfa fields, insecticide choice may be an important tool for protecting water quality. In addition, consideration should be given to the fact that pyrethroids, while they proved advantageous in these experiments, can affect beneficial species and do have high toxicity to fish at extremely low concentrations.
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Also in this issue:Reuse of Drainage Water for Irrigation: Results of Imperial Valley Study: I. Hypothesis, Experimental Procedures, and Cropping Results
Reuse of Drainage Water for Irrigation: Results of Imperial Valley Study: II. Soil Salinity and Water Balance
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Letter: Climate debate heats up
Sun setting on water quality exemptions
Rapid test helps dairies manage wastewater
Marin ranchers bullish on grass-fed livestock
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