Effects of Some Meteorological Parameters and Formulation on Phytotoxicity of the Fungicide Captan

Background: This study investigated the effects of some important meteorological parameters and filler type compounds on phytotoxicity of captan in peach trees in the north of Iran. Captan is a phthalimide fungicide which has frequently been used in northern regions of Iran to control certain plant diseases. This fungicide has caused intense phytotoxicity in peach trees which was first observed in the northern districts of Iran in 2005. Since early research has only reported that some changes in the climate could be associated with this phytotoxic effect and little is known on phytotoxicity of filler in the formulation, therefore, we studied the role of filler in this toxic effect and also its interaction with this phytotoxicity. Methods: Filler (calcium carbonate) and climatic parameters, including minimum and maximum temperatures, relative humidity, daily precipitation, and sunshine hour, were analyzed. Results: The means of calcium carbonate concentrations measured by atomic absorption and EDTA analyses were 17.41± 0.4 and 20.93 ± 1.25 µg /ml, respectively. The final ranges of calcium carbonate in formulation were found to be 42-43.5%. pH values were measured from 8.55 to 8.75. Furthermore, there were no significant differences between meteorological parameters in the year 2005 in comparison with previous year (P>0.05). Conclusion: The high amounts of calcium carbonate in the formulation of captan, resulting in alkaline hydrolysis followed by the increasing uptake of thiophosgen in peach trees and consequently interacting with meteorological parameters, have caused a broad spectrum of phytotoxicity in northern areas of Iran.