The eyes of many farmers and at least one fungicide manufacturer are focused firmly on prevention in dealing with soybean rust in Brazil and in the US this year. While it might be more cost effective for farmers if failsafe curative fungicides were more widely available, the preventive treatments from Syngenta that growers used this year in Brazil's Parana state by all appearances offer reliable protection.

Continue article

ADVERTISEMENT

"The information about rust currently available is excellent if it is used correctly, and the available crop protection products have worked very well at preventing losses to the disease," Brazilian farmers Armin and Rubens Kliewer (above) told Agriculture Online Thursday afternoon in Brazil's Ponta Grossa county. The interview was part of a crop tour for American ag journalists in the southeastern part of the country lead by Syngenta.

"Three years ago, when rust was new in the region, we were in a bit of a panic about it, and thought the treatments were very expensive," Armin said through a translator. Today they are still concerned but mostly because even though they have effective treatments it is still difficult to identify the disease in their fields. "The first symptoms are easy to miss," he says.

Armin and Rubens together farm about 400 hectares (just under 1,000 acres) near Ponta Grossa. The father and son duo, along with Rubens' two brothers, raise a total of about 800 hectares (about 2,000 acres) of crops in three Brazilian states. They call their farm Fazenda Cachoeirinea.

One preventive application did the trick

The Kliewers have used preventive treatments of azoxystrobin (a strobilurin fungicide) and several different triazoles mostly, according to their agronomy consultant José Luiz Buss. This year they only needed to make one application on their acreage in Ponta Grossa because of the drought there, and because rust didn't appear nearby until very close to harvest.

Armin says at this point in the timeline of the disease they are more concerned with efficiency in getting treatments onto the crop than they are with resistance to the chemistries.

Aerial applications aren't used frequently in their part of the country because farm sizes are small and the terrain is uneven. That means they must use ground sprayers in a very short application window.

"The main thing is to keep monitoring and not let rust affect crops," Armin says. "Timing is everything." That was the gist of the message to US growers from several other independent and corporate farmers in the region this past week as well.

In addition to sentinel plot programs organized and monitored by industry and government organizations, a common practice in the south of Brazil is for farmers to plant their own sentinel plots 20-30 days ahead of their main soybean plantings.

Trained agronomists who work on the farms scout these plots carefully every few days for signs of rust. If they find it, they spray their main soybean crops with a preventive treatment a few days before their equivalent of the R1 stage. They call this stage "first flowering" because they raise soybeans that grow as long as conditions are favorable.

Why isn't resistance as great a concern as application timing?

"It is a relatively new fungal disease of crops with relatively new chemistries available to treat it," Syngenta spokesperson José Sergio Osso explained.

Brazilian farmer wishes for better curatives

Armin says their main hope looking forward is that more research money will be spent developing effective curatives for rust.

"A disease management strategy based on curing an existing problem would be cheaper for us in the long run than one based on prevention of a potential threat," Armin says.

Syngenta continues to conduct research and development into making more effective products, and that includes anything that may be curative for soybean rust, says Mike Vanausdeln, a spokesperson for Syngenta Crop Protection, who took part in the crop tour. The products they plan to introduce in the US for this growing season, however, are mainly preventive.

This year, the Kliewers used a Syngenta product called Priori Xtra. Once it receives regulatory approval, the fungicide will be marketed as Quadris Xtra in the US, according to Vanausdeln. Quadris Xtra, which uses the active ingredients azoxystrobin and cyproconazol, is both a preventive and curative, containing chemistries classified as triazoles and strobilurins.

Ninety percent of the effectiveness of preventive fungicides in terms of preventing yield loss to rust is achieved when the first application is made just before the R1 stage, according to research done by Olavo Correa da Silva, with Fundacao ABC, a private research firm that serves three large Brazilian cooperatives. Some additional benefit can be realized from a second application, but it's not a dramatic difference, da Silva says.

"We are optimistic that Quadris Xtra will get Section 18 approval in the US for the upcoming growing season," Vanausdeln told Agriculture Online on Thursday. He said he thinks supplies of the fungicide should be sufficient to meet demand.

Syngenta also will offer a pre-mix of Quadris and Tilt in the US this year. Called Quilt, the product uses the active ingredients azoxystrobin and propiconazol. It, like Quadris Xtra, is a strobilurin-triazole combination.

"Section 18 approval for that product is expected shortly," Vanausdeln says. The company has been encouraging growers to use a tank-mix of the two separate fungicides up to this point, but, he says, the Quilt premix is the same thing in a form that's easier to use.

Photos by Cheryl Rainford: Top photo (Left to right): José Luiz Buss, Rubens Kliewer and Armin Kliewer. Armin and his son Rubens farm about 400 hectares in Brazil's Parana state, near Ponta Grosso. Rubens' two brothers farm another 400 hectares in Bahia and Mato Grosso states. Buss is a private agronomy consultant who works with their farm. Bottom photo: Early signs of Asian soybean rust can be difficult to spot since they look like several other leaf diseases. This photo was taken last week in a test plot near Castro, in Brazil's Parana state.