Responses in root growth, nitrogen metabolism and nutritional quality in Brachiaria with the use of thiamethoxam

This study investigated the effects of using increasing doses of thiamethoxam, a neonicotinoid insecticide, applied as seed treatment, on the physiological, biochemical and nutritional composition of Brachiaria brizantha cv. Piata. We conducted two experiments with B. brizantha in a greenhouse, in the absence of insects. Biometric parameters and nutritional quality, for feed, were measured in the first experiment, and the root system and the leaf nitrate reductase activity were analyzed in the second experiment. The doses of: 0, 17.5, 35.0, 70.0 and 140.0 g of thiamethoxam per 100 kg of seeds, were applied in both experiments. The results show that the seed treatment with thiamethoxam resulted in a slight decrease in shoot development, but provided root growth, which led to an increase in the nitrate reductase activity that resulted in the higher crude protein content in the shoot. Our data indicate that thiamethoxam alters the metabolism and physiology of B. brizantha, and improving the feed quality is thus becoming a technological tool to be applied to crops.