Changes in pest management practice in almond orchards during the rainy season in California , USA
In California, regulatory agencies are concerned about organophosphate (OP) contamination of surface water. OPs originate in part from applications on dormant almond and stone fruit orchards that are washed off during winter rainstorms. Programs conducted by the University of California Statewide Integrated Pest Management Project, University of California Cooperative Extension, and the Biologically Integrated Orchard Systems (BIOS), a coalition of public and private groups, have promoted the replacement of OPs on almonds during the rainy season with alternative practices. Data from individual applicator records from the California Pesticide Use Reports demonstrated that during 1992–1997, almond growers in all nine major almond-producing counties significantly reduced use of OPs. The area of almond orchards treated with OPs during the dormant season was reduced by 40–55%, depending upon the region. Similarly, the percentage of growers who used OPs during the dormant season was reduced by 31–48%, and the mass of OPs applied to almond orchards during the dormant season was reduced by 22–57%. During the same period, there was a significant increase in the percentage of growers who used “reduced-risk” treatments: the microbial pesticide Bacillus thuringiensisat bloom-time, oil without an insecticide during the dormant season, and no treatment during the dormant or bloom season. In addition to the decrease in OPs during the dormant season, there was a significant decrease in the area treated with OPs during the growing season. However, there was also a significant increase in the use of pyrethroids during the dormant season, a practice that might result in some surface water and sediment contamination. © 2001 Elsevier Science B.V. All rights reserved.
Concentrations, transport and biological effects of dormant spray pesticides in the San Francisco Estuary, California
The transport and biological effects of dormant spray pesticides were examined in the San Francisco Estuary, California, by measuring dissolved-pesticide concentrations and estimating toxicity using bioassays at a series of sites in January and February 1993. Distinct pulses of pesticides, including diazinon, methidathion, and chlorpyrifos, were detected in the San Joaquin River in January and February and in the Sacramento River in February following rainfall. The higher pesticide loads in the Sacramento River compared with those in the San Joaquin River can be attributed to the greater amount of rainfall in the Sacramento Valley. The use patterns and water solubility of the pesticides can account for the observed temporal and spatial distributions in the two rivers. The pesticide pulses detected at Sacramento were followed through the northern embayment of San Francisco Estuary. In contrast, the pesticide distribution in the Sacramento-San Joaquin Delta changed from distinct pulses to steady increases in concentration over time. Seven-day bioassays indicated that Sacramento River water at Rio Vista was acutely toxic to Ceriodaphnia dubia (water flea) for 3 consecutive d and San Joaquin River water at Vernalis for 12 consecutive d. These water samples all had the highest diazinon concentrations. Examination of 96-h LC50 values (lethal concentration that kills 50% of test organisms in 96 H) indicates that measured diazinon concentrations could account for most but not all the observed toxicity. Other pesticides present could contribute to the toxicity.
Analysis of pesticides in seawater after enrichment onto C8 bonded-phase cartridges.
Apres l'enrichissement sur cartouche de silice C 8 , on analyse par chromatographie en phase gazeuse les pesticides suivants: le lindane, le chlordane, l'endosulfan, le fenvalerate, le methyl parathion, le fenitrothion et le malathion