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 In tegrated Pest Management Project, University of California Cooperative Exte nsion, and the Biologically Integrated Orchard Systems (BIOS), a coalition of public and private groups, have promoted the replacement of OPs on almon ds 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 co unties significantly reduced use of OPs. The area of almond orchards treate d 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 do rmant season was reduced by 31-48%, and the mass of OPs applied to almond o rchards during the dormant season was reduced by 22-57%. During the same pe riod, there was a significant increase in the percentage of growers who use d "reduced-risk" treatments: the microbial pesticide Bacillus thuringiensis at bloom-time, oil without an insecticide during the dormant season, and n o 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 contaminatio n. (C) 2001 Elsevier Science B.V. All rights reserved.