Brazil states impose soybean planting limits to control rust

To prevent and control the Asian rust on soybeans, the Brazilian states of Mato Grosso and Mato Grosso do Sul established new phytosanitary measures. The revision of the current states legislation aims to reduce soybean planting “window” to delay rust resistance to fungicides in the market. 

 

The Asian rust on soybeans, first reported in Brazil in 2001, is the disease with the biggest economic impact. The average cost to control the disease with fungicide is estimated at nearly $2 billion each season, according to the Anti-Rust Consortium. Even though there is a huge contribution of fungicide to control rust, the efficiency reduction has been observed due to the repeated use of the same products.

 

Embrapa researcher Cláudia Godoy explained that of the three fungicides groups used to control rust, two already presented decreased efficiency because of the fungus adaptation of these products. "Every effort is being made to stabilize the fall of efficiency and extend the life cycle of the third group, which entered the market in 2013", said Godoy.

 

To face this, the Crop Protection Agency of Goiás established a timetable for soybean seeding in the state of Goiás. From now on, that the soybean crop cannot be sown in the state between October 1 and December 31. "This measure is important because it reduces late soybean plantings and the off-season soybean crop," emphasized Godoy. "The late plantings receive fungus inoculums from early planted areas, which increases the number of sprayings and reduces spray intervals. This excess of fungicides spraying exerts a very high selective pressure and favors the fungicide resistance," explained by Godoy.

 

The state of Mato Grosso also published a normative instruction, anticipating in 45 days a period for fallowing, which now runs from May 1 to September 15 (and no later than June 15 to September 15). "This measure has the same goal, as it limits late planting. Mato Grosso has opted for an increase of fallowing once the technicians (agronomists) believe it is feasible" said the Embrapa researcher.

 

"After the entrance of Rust in Brazil, soybean crops has become dependent on fungicide in order to obtain high productivity. If fungicides continue to lose efficiency, this will have an impact in all the productive system, with productivity reductions all over Brazil," alerted by Claudia Godoy.