Workshop brings together production chain to discuss soybean rust

The high cost of controlling Asian rust (average of US$2,8 billion per harvest), as well as the consequences of the resistance of the fungus that causes the disease (Phakopsora pachyrhizi) to fungicides, the reduction in the efficiency of these products and existing strategies to ensure the sustainability of soybean production permeated the discussion this Thursday (30) and Friday (31) during the Workshop on Asian Soybean Rust: current situation and challenges .

The event coordinated by the Ministry of Agriculture, Livestock and Supply (Mapa), at the Assis Roberto de Bem Auditorium, at Embrapa Genetic Resources and Biotechnology, in Brasília (DF) brought together around 90 representatives from the soybean production chain. Participating in the event were: Department of Plant Health and Agricultural Inputs, the Secretariat of Agricultural Defense of Mapa, the Brazilian Agricultural Research Corporation (Embrapa), entities from the productive sector, as well as representatives of State Agricultural Defense Bodies from the main producing states of soybeans in Brazil.

For the event coordinator, Graciane Castro, from the National Asian Soy Rust Control Program (PNCFS) of the Ministry of Agriculture, Livestock and Supply (Mapa), the objective is to standardize information from scientific research, regulatory experiences, demands and impacts on the soybean sector caused by the disease. Graciane presented the legislative measures to manage the disease in Brazil, such as the sanitary void and the soybean sowing schedule.

The sanitary void is a period of at least 60 days without live soybean plants in the field. “The objective of the sanitary void is to reduce the survival of the fungus that causes Asian rust during the off-season and thus delay the occurrence of the disease during the harvest,” he says. In Brazil, 13 states and the Federal District adopted this measure, established through regulations.

Embrapa Soja researcher Cláudia Godoy, who was also a speaker, reinforced the importance of these measures as important strategies for managing the disease. When justifying the importance of the sanitary void, Claudia explained that the fungus that causes Asian rust is biotrophic, which means that it needs a living host to develop and multiply. “By eliminating soybean plants in the off-season,” we break “the disease cycle, thus reducing the amount of fungus spores present in the environment,” she says. “Hence, the importance of maintaining the sanitary void”, she highlighted.

Sowing calendar - The other legislative measure in force in Brazil is the sowing calendar, which provides for the determination of a deadline for sowing soybeans during the harvest. It is established by state regulations in seven soybean-producing states: Goiás, Mato Grosso, Paraná, Santa Catarina, Tocantins, Bahia and Mato Grosso do Sul. The objective of the schedule is to reduce the number of fungicide applications throughout the harvest and, with This reduces selection pressure for fungus resistance to fungicides.

Godoy reinforces that populations that are less sensitive to the fungicides "triazoles", "strobilurins" and "carboxamides" have already been found in the field. The researcher explains that late soybean sowings can receive populations of the fungus already at the beginning of the crop's development, which requires the use of fungicides to be brought forward and demands a greater number of applications. “The greater the number of applications, the greater the exposure of the fungus to fungicides and the greater the chance of accelerating the process of selecting populations resistant to these fungicides”, she reinforces. “And despite the contribution of fungicides, a reduction in the efficiency of products available on the market has been observed since the 2007/08 harvest due to the adaptation of the fungus”, she explains.

Market perspective - During the event, the sowing window in the management of Asian soybean rust was the topic of a panel during the Workshop, which included the participation of the production sector. To address future scenarios from the perspective of Asian rust management, the president of the Brazilian Agribusiness Association (ABAG), Luiz Antonio Pinazza, was invited.

The discussion on the demand of the productive sector in relation to the soybean sowing calendar was presented by the president of Aprosoja Brasil, Bartolomeu Braz Pereira. “Rust brings economic impacts to rural producers and great concerns. Today, fungicides, alongside seeds, are the inputs that most impact production costs,” he highlighted. “Therefore, we need to make decisions supported by scientific research to avoid greater losses”, he argues. Pereira also highlighted that Aprosoja defends the production of its own seed – as an alternative to reduce costs – but in Mato Grosso, this practice has been hampered by current legislative measures.

The view of the Brazilian Agriculture and Livestock Confederation (CNA) on the limit of the soybean sowing window was presented by the president of the institution, Luís Alberto Novaes, who defended the relevant role of research, but warned of the need to highlight the vision of each state.

The president of Cooperativa Bom Jesus, Luiz Roberto Baggio, representing the Organization of Brazilian Cooperatives (OCB) also said he agrees with the importance of research to define the sowing schedule, but understands that the particularities of each state should be considered. Baggio showed special concern about Paraná. “The difference in the soybean calendar between crops in the southwest of Paraná and Santa Catarina, which are often neighbors, generates dissatisfaction among producers in the southwest of the state who feel harmed”, he reflects.

Genetic variability and other views - To present aspects of the genetic variability of the fungus Phakopsora pachyrhizi, professor Sergio Hermínio Brommonschenkel, from the Federal University of Viçosa (UFV) highlighted that the fungus' variability mechanism promotes adaptation to the different control measures available for the rust, both for genetic and chemical control. “Mutation is a natural mechanism, therefore, efforts must be directed towards trying to reduce the fungus population and maintain its adaptive capacity more restricted”, emphasized Brommonschenkel.

There was also space for the presentation of the monitoring of fungus resistance to fungicides in a lecture given by the president of the Rust Resistance Action Committee (FRAC), Luiz Demant. “We have been monitoring the resistance process in Brazil and the role of FRAC is to encourage the adoption of existing good practices to reduce the impact of resistance on Brazilian crops and maintain the efficiency of fungicides for longer”, he highlighted.

The representative of the National Plant Defense Association (Andef), Fábio Kagi, presented a survey of the 16 fungicides that are in the registration phase. Of the total, 10 are from groups already used to control soybean rust and 6 of them should not be recommended for soybeans. “These new products have similar modes of action to those already used, yet they will bring greater efficiency to the management of the disease”, he argues. “I also emphasize that it is very important to adopt integrated rust management strategies, with respect to legislative measures, so that the useful life of fungicides can be extended for longer”, he highlighted.

The lecture on the consequences of late soybean cultivation for insecticide resistance was addressed by Daniela Okuma, from the Brazilian Insecticide Resistance Committee (IRAC). The workshop concluded with a lecture by Embrapa Soja researcher, Francisco Krzyzanowski, on technologies for seed production. The researcher presented results on seed quality in Brazil in three harvests (2014/15; 2015/16 and 2016/17), whose data were collected in samples from 12 states. Krzyzanowski showed that Brazil has high levels of soybean seed germination and vigor. In the 2016/17 harvest, the average germination was 91%. “In Mato Grosso - the largest soybean producer -, for example, the average was 93%, revealing that there are technologies in Brazil for producing quality soybeans”, he highlighted.

Regarding seed vigor, in the 16/17 harvest, the national average was 82%. The state of Mato Grosso surpassed the national average, reaching 84% seed vigor. “These data give an overview of the excellent quality of the soybean seed produced in Brazil”, highlighted Krzyzanowski. The researcher also presented which factors can interfere with the quality of the seed, such as mechanical damage during the harvest or attack by stink bugs, for example. “Even so, we have technologies available to overcome all the factors that affect the quality of soybean seeds in the country”, he concluded. The director of the Department of Health, Plants and Agricultural Inputs of the Ministry of Agriculture, Carlos Goulart, led the closing discussions of the event.