In late February, a Louisiana contingent — part of a larger group — returned from a tour of Brazil with a much greater understanding of Asian soybean rust than expected.
The Brazilian people we met across the country had a very common thread of hospitality and friendliness. Everyone — from producers to agribusiness personnel — was willing to share with us his experience with rust.
A lot of amount of information was collected to be sorted for its validity here in the United States.
Rust is the largest problem Brazil has to deal with in soybean production. It is so prevalent in part because environmental conditions are perfect for its survival and spread. Optimal temperatures, dews and little to no cold temperatures are ideal for rust to become an epidemic every year.
In addition, growing two crops annually magnifies the rust problem.
Big advantages for the United States are that we do have winter and we grow one crop a year. Granted, rust can overwinter in the United States, but it may be a situation where the disease has to start over following a severe winter.
Brazil is just beginning to scratch the surface of its potential. Infrastructure and governmental policies are keeping the country from becoming more of a world player in areas other than agriculture, which will be the economic driving force for many years to come.
We were able on this tour to better understand what is going on in Brazilian soybean production. One thing noted was the weediness of some fields in certain parts of the country. The fields were primarily conventional beans and most fields were planted flat on 20-inch or less row spacings. Some producers are beginning to go to a wider row spacing to improve rust control.
Farm equipment was modern but smaller than I anticipated. The largest self-propelled spray rig we saw had a 90-foot boom. Most large farms we visited had three or four tractor-pulled spray rigs with 30- to 70-foot booms. They also use airplanes for spraying.
Farm size has something to do with the effectiveness of spraying for rust. Most farms we visited had no less than 15,000 acres of beans and other crops too. There is little to no staggering of plantings, so most of the soybean crop goes into the reproductive stage at about the same time. Some fields are sprayed more than twice because of the timing of the first spray and the coverage.
Compound selection at the first application is critical. Coverage on the first spray is very important in the management of soybean rust. If you do not do a good job on the first spray, you set yourself up for less control with the second spray, which could lead to a third spray.
Most sprays are put out at R1 or as close to R1 as possible. A ground rig is preferred. Some hedging takes place because of logistics. They have to start at some point to be able to cover 20,000 acres.
Another point discussed everywhere we went was spray volume. Someone said that water is the cheapest thing in a tank. Most ground rigs are spraying 12 to 16 gallons per acre; aerially no less than 5 gallons per acre or 3 gallons per acre with oil. Spray volume is critical in controlling rust.
Some producers were using primarily hollow cone nozzles at no less than 80 psi. Others were pleased with the results they got with double flat fan tips angled at 30 degrees. A great deal of spray nozzle research is being conducted by private industry and universities.
Rust suppression or control varied a great deal with application method, timing and products used. We were able to observe fields that had had two ground fungicide applications and were not going to be sprayed again before harvest. On the other extreme, we walked in some fields that had been sprayed up to four times and decisions were being made whether or not to spray again.
That goes back to effectiveness in spraying — it is critical.
Information on Asian soybean rust and management are readily available from many sources, primarily the Internet. The LSU AgCenter soybean rust site, http://www.lsuagcenter.com/subjects/soybeanrust, contains suggestions on how to manage soybean rust. USDA has posted a new soybean rust site, which can be accessed at www.usda.gov/soybeanrust.
Most of the well-managed fields in Brazil are treated an average 2.3 times — very efficiently and in a timely manner — and managed to reduce crop stresses during the growing season (a key part in controlling the disease). We have fungicides that will control rust, but we need to stay on top of the situation.
David Y. Lanclos is the soybean, corn and grain sorghum specialist at LSU AgCenter. e-mail: [email protected]