Production Journal

Farm Journal, May 19, 2007 by Roger Bernard

Soy Rust Spray Tips

After a few years of real-life experience, recommendations on the most effective methods to spray for Asian soybean rust are being tweaked. "It's all about achieving medium droplet size," says University of Illinois Extension specialist Scott Bretthauer.

Nozzle pressure affects droplet size, spray volume and velocity. It's important to select a nozzle type, orifice size and pressure to achieve the flow rate for the application and create a medium droplet. Groundspeed is also critical, Bretthauer explains. "Be honest when calibrating the sprayer, and try to keep speed variation as little as possible," he adds.

Since soybean rust begins on the lower leaves, it's critical to deposit fungicides into the lower canopy. That's fairly easy at the R1 growth stage, but it gets harder as the canopy gets taller and more dense.

Several farmers bought twin spray nozzles in anticipation of soybean rust. Now, research at Ohio State University and Kansas State University is showing single flat fans improved canopy penetration in later growth stage (R5) soybeans.

Air assist and pulse width modulation technology are effective on rust. But, Bretthauer says any sprayer will work with accurate calibration and attention to detail. Aerial applications will be key if rust gets a foothold, he adds.

Constructing the Prospective Plantings Report

Seldom has there been as much anticipation leading up to a Prospective Plantings report than there was for the March 30 release. Where does USDA come up with these numbers, though, and how do they compare with the figures released in the June report throughout the years?

The acreage estimates reports are based primarily on farmer surveys conducted during the first two weeks of March. According to USDA: "The March Agricultural Survey is a probability survey that includes a sample of more than 86,000 farm operators selected from a list of producers that ensures all operations in the U.S. have a chance to be selected. These operators are contacted by mail, Internet, telephone or personal interview."

Looking back, planted corn acreage has increased in the June Acreage report compared with the March Prospective Plantings report in six of the last 10 years (1997 to 2006). The average increase has been almost 875,000 acres; the average decline has been slightly more than 620,000 acres.

The range of increases from the March to the June report: The smallest increase was 17,000 acres in 1998; the largest increase was 1.964 million acres in 2004. The range of decreases: The smallest decrease was 100,000 acres in 2003; the largest decrease was 1.189 million acres in 1997.

See "Seismic Acreage Shifts" on page 30 for a recap of the March 30 report.