PW09 Pesticide I
8:00 AM - Wednesday
(PW160) Historical perspective of pesticide use in the Colorado River delta, and impacts on avian health.
Garcia-Hernandez, J.1, Vega-Cazares, M.2, Sapozhnikova, Y.3, Shlenk, D.3, Garcia-de-la-Parra, L.2, Betancourt-Lozano, M.2, 1 Centro de Investigacion en Alimentacion y Desarrollo (CIAD) Guaymas, Guaymas, Sonora, Mexico2 Centro de Investigacion en Alimentacion y Desarrollo (CIAD) Mazatlan, Mazatlan, Sinaloa, Mexico3 U.C. Riverside, Riverside, CA, U.S.A.
ABSTRACT- Pesticide use in the delta of the Colorado River has changed from the intensive use of organochlorine compounds to the application of the newer organophosphate, pyrethroid and carbamate substances. In the 70s, DDT was the pesticide of choice for cotton crops in the Colorado River delta. The dose was 5 kg/ha of DDT resulting in the application of more than 440,000 kg of DDT in one season. In the last fifteen years, crops have changed from cotton to grains and, as consequence; the pattern of pesticide use has also been modified. The pesticides used for these crops are mostly organophosphates followed by pyrethroids and carbamates, some of them reported as highly toxic to birds. The Colorado River delta is a nutrient rich wetland, home of 213 species of birds, including some endangered species. The objective of our study was to determine the effects of organochlorine pesticides in nest success of three bird species and to evaluate the levels of cholinesterase inhibition in cattle egrets from the Colorado River delta wetlands. Our results showed that DDT and DDE are still present in 100% of the egg samples analyzed, although levels were below 20 ng/g, which are considered lower than the threshold concentration established for birds. On the other hand, cholinesterase activity in cattle egrets was inhibited in 30% of the samples analyzed during 2003-2004 crop season, with inhibitions ranging from 5 up to 45%. PCBs were also analyzed in egg tissues finding elevated concentrations in aquatic birds compared to terrestrial birds. Therefore, past and present pesticide use in the Colorado River delta affected and is still potentially affecting avian health. We recommend to continue monitoring, both resident and migratory bird populations, and to evaluate nest success in different species in order to protect avian health in this important area.
Key words: avian health, colorado river delta, pesticides