Is the application of carbendazim harmful to healthy plants? Evidence of weak phytotoxicity in tobacco.

To understand the phytotoxic effects that certain bezimidazole fungicides exert on plant growth, the aim of the present study was to determine the effect of the fungicide carbendazim, on foliar biomass, pigment content, and nutrient levels in tobacco plants (Nicotiana tabacum L. cv. Tennessee 86). The fungicide applied was carbendazim with a purity of 100%, at three different rates: 1.3 mM (carb1), 2.6 mM (the recommended concentration, carb2), and 5.2 mM (carb3). The control treatment was without carbendazim. The application of dosages of this fungicide lower than recommended (1.3 mM) resulted, on the one hand, in greater dry weight and, on the other, higher carotenoid concentrations, as well as higher N and K concentrations with respect to control. On the contrary, the application of the carbendazim dosage higher than recommended (5.2 mM) caused a decrease in dry weight and in all of the foliar pigments, as well as all of the nutrients, with respect to the other dosages and control. These results appear to indicate that besides its direct antibiotic action against pathogens, the effects of this fungicide in plants could be dangerous, especially at higher dosages. Nevertheless, the negative effects of carbendazim can be avoided by reducing the amount applied in current agriculture.