ABSTRACT
The present study aimed to evaluate the action of both the site-specific fungicide carbendazim + tebuconazole and the multisite fungicide chlorothalonil, in vitro, on the germination of Phakopsora pachyrhizi uredospores and, in vivo, on the severity of symptoms of the disease in soybean leaflets. The uredospores of Phakopsora pachyrhizi used in the experiments were collected from Artur Nogueira, São Paulo State, during field trials carried out in three growing periods within the 2016/17 season. For each sowing period, three different cultivars, susceptible to Asian soybean rust, were used according to the recommendations for their respective maturation group (early, medium and late), totaling 9 cultivars, i.e., 9 samplings. The action of both the multisite fungicide chlorothalonil and the site-specific fungicide carbendazim + tebuconazole was evaluated on the germination of urediniospores, in vitro, and on the disease severity, in vivo, by the method of detached leaves, preventively treated before inoculation. Lethal concentrations LC50 and LC95 were determined by the Probit method. The multisite fungicide chlorothalonil was more fungitoxic in vitro and in vivo than the specific fungicide carbendazim + tebuconazole to P. pachyrhizi uredospores in all samplings, regardless of seasons and sowing times. The in vivo and in vitro tests indicated significant interaction of the cultivars with each fungicide.
Keywords
uredospores germination; Asian soybean rust;
Glycine max