Publication evaluates the efficiency of fungicides to control soybean rust

Embrapa has just launched the publication  Efficiency of fungicides to control Asian soybean rust, Phakopsora pachyrhizi, in the 2019/2020 harvest: Summary results of cooperative trials.  The publication is the result of cooperative trials carried out in the 2019/2020 harvest in different producing regions (Rio Grande do Sul, Paraná, Mato Grosso, Mato Grosso do Sul, Goiás, Bahia, Minas Gerais and Distrito Federal) by 23 public research institutions and private companies, components of the Fungicide Assessment Network for Disease Control in Soybeans. 

According to researcher Cláudia Godoy, from Embrapa Soja, network experiments have been carried out since the 2003/2004 harvest to compare the efficiency of registered fungicides and those in the registration phase for controlling Asian rust. “This harvest, three experiments were carried out, with registered fungicides, in the registration phase and with fungicides made up of single active ingredients to monitor changes in the sensitivity of the fungus P. pachyrhizi”, she explains. 

The results of the Network are relevant for the continuity of research and rural extension work, as well as presenting information that can assist technicians and producers in making more efficient decisions for managing the disease. “Asian rust experiments are carried out in late sowings, starting in November, to guarantee the presence of the disease, but this is not the situation in many crops in Brazil that have shown disease escape or late incidence due to the sowing time. The results must be appropriate to the sowing time and situation in the region, always prioritizing the rotation of fungicides”, explains Godoy. 

Disease management

Asian soybean rust is one of the most severe diseases affecting soybean crops, with damage ranging from 10% to 90%. The management strategies recommended in Brazil for this disease include: sanitary vacuum (absence of soybean sowing and the elimination of volunteer plants in the off-season through sanitary vacuum to reduce the fungus), the use of early cycle cultivars and sowing in beginning of the season - recommended as a strategy to escape the disease -, the use of cultivars with resistance genes, monitoring the crop from the beginning of its development, the use of fungicides preventively or at the appearance of symptoms and the reduction of sowing windows to reduce the number of fungicide applications throughout the season and thus try to delay the selection of fungal populations that are resistant or less sensitive to fungicides.