ABSTRACT
Black flies, a non-target species of the insecticides used in fruit production, represent a severe medical and veterinary problem. Large increases in the level of resistance to the pyrethroids fenvalerate (more than 355-fold) and deltamethrin (162-fold) and a small increase in resistance to the organophosphate azinphos methyl (2-fold) were observed between 1996-2008 in black fly larvae under insecticide pressure. Eventually, no change or a slight variation in insecticide resistance was followed by a subsequent increase in resistance. The evolution of pesticide resistance in a field population is a complex and stepwise process that is influenced by several factors, the most significant of which is the insecticide selection pressure, such as the dose and frequency of application. The variation in insecticide susceptibility within a black fly population in the productive area may be related to changes in fruit-pest control. The frequency of individuals with esterase activities higher than the maximum value determined in the susceptible population increased consistently over the sampling period. However, the insecticide resistance was not attributed to glutathione S-transferase activity. In conclusion, esterase activity in black flies from the productive area is one mechanism underlying the high levels of resistance to pyrethroids, which have been recently used infrequently. These enzymes may be reselected by currently used pesticides and enhance the resistance to these insecticides.
Subject(s)
Animals , Azinphosmethyl , Esterases/metabolism , Insecticides , Nitriles , Pyrethrins , Simuliidae/drug effects , Argentina , Biological Assay , Insecticide Resistance , Simuliidae/enzymologyABSTRACT
Aunque el manejo integrado de plagas se aplica en forma creciente en la Región Norpatagónica, todavía una amplia gama de plaguicidas es utilizada con el fin de controlar apropiadamente las principales plagas agrícolas. Otros agroquímicos también son aplicados en las actividades industriales asociadas. El objetivo del presente trabajo es evaluar el impacto potencial causado por estos plaguicidas sobre los organismos acuáticos y para ello se utilizan datos bibliográficos de toxicidad aguda y resultados analíticos locales. Se utilizó un procedimiento escalonado, permitiendo la selección de aquellos xenobióticos ambientales que justificarían un estudio de ecotoxicidad posterior. Los residuos máximos de metil azinfos (S-(3,4-dihydro-4-oxobenzo[d]-[1,2,3]-triazin-3-ylmethyl)O,O-dimethyl phosphordithioate), indican la probabilidad de efectos agudos en el 37% de las especies estudiadas en el río, principalmente peces y zooplancton. Este valor se incrementa en los drenajes hasta un 42%. En el caso del carbaril (1-napthylmethylcarbamate) los residuos encontrados en drenajes afectarían al 14% de las especies estudiadas, mientras que en el río el impacto es despreciable.
Although the Integrated Pest Management (IPM) is increasingly being applied in the Northern Patagonia Region, different pesticides are still used in order to properly control agricultural pests. Other agrochemicals are also applied in the agriculture associated activities like conservation and packaging industries. The potential impact caused by these pesticides on aquatic organisms is assessed in the present study by means of acute toxicity data available in the literature and local analytical results. A tiered procedure was used allowing the selection of those environmental xenobiotics that need further ecotoxicity studies. The observed maximum residues of azinphos-methyl, (S-(3,4-dihydro-4-oxobenzo[d]-[1,2,3]-triazin-3-ylmethyl) O,O-dimethyl phosphordithioate), indicate the probability of acute effects in 37 % of the studied species in the river, mainly fish and zooplankton.This value increased in drainage channels samples up to 42 %. Additionally, carbaryl (1-napthylmethylcarbamate) residues foundin drainage channels affect 14 % of the studied species, while in the river samples the impact was negligible.