Best way to control soybean rust is multipronged approach

The 8th Brazilian Soybean Congress wrapped up its four day meeting Thursday in the city of Goiania in the state of Goias. One of the goals of the Congress, which was sponsored by Embrapa, was to elaborate the path forward for the control of soybean rust disease.

Soybean rust is native to China and it was first identified in Brazil during the 2000/01 growing season and it quickly became the most important disease infecting Brazilian soybean production. The disease is now present in all the soybean producing regions of Brazil and Brazilian farmers spend approximately US$ 2.2 billion per year on control measures. That cost does take into account lost production caused by the disease. If the disease is not adequately controlled, the disease can cause losses of 30% to 90%.

Scientists emphasized that the best way to control the disease was a multipronged approach. A simple way for farmers to save on control measures is to get ahead of the disease by planting early maturity soybeans as early as possible. Brazilian farmers have been planting more early maturity soybeans year after year. These 95-day maturity soybeans may be ready for harvest before the disease becomes a widespread problem. Another way to help control the spread of the disease is to adhere to the soybean-free period that has been established in most Brazilian soybean producing states.

Currently, the best method of control is the use of approved fungicides, but many of the fungicides on the market have been losing their effectiveness due to the disease developing resistance. Scientists advise farmers to use a mixture of fungicides with different modes of action to help mitigate the development of resistance.

Farmers may also want to plant two soybean varieties currently on the market that exhibit improved resistance to the disease. These varieties have one-gene resistance and scientists are working on multi-gene resistance that will offer more durable protection. Ultimately, the goal is to incorporate resistance genes without giving up high yields or resistance to herbicides and insects.

In order to do that, scientists are trying to better understand the disease. They have already identified 851 different proteins that the disease injects into an infected soybean plant. The goal is to identify which of the proteins elicits the plant's own response mechanism. That knowledge, along with the complete DNA sequencening of the disease, may enable scientists to develop complete resistance to the disease. Scientists are hopeful they will reach that point within the next decade.

The Congress was attended by 2,300 people involved with all aspects of soybean production and it included 5 different conferences, 50 presentations, 16 panels, and 340 scientific posters.