Asian soybean rust may have been the most hyped fear, but a late-season dry spell will be a much larger factor in deciding Georgia's yields.
“Our crop is comprised of a few Group 4 varieties, some Group 5 and Group 6 and a lot of Group 7,” said Phil Jost, Georgia Extension soybean specialist on Sept. 22. “Most of the Group 4 varieties have already been harvested. The Group 5 and Group 6 varieties are either being harvested or close to it. Our Group 7 varieties are almost at R-6.
“So the majority of our crop is past the point where we're concerned with soybean rust. Rust hasn't been as big a worry for the past two weeks.”
Even with rust lurking, the state was expecting a great soybean yield. “It looked phenomenal — USDA had us pegged at around 33 bushels per acre. That would have tied a record we set a few years ago.”
However, positive expectations have been quieted in the past couple of weeks. Since Labor Day, the state has suffered from a lack of rain.
“Our beans will be hurt,” said Jost. “I have no doubt the Group 7s will take a yield hit due to this dry weather.”
Although a lack of moisture has slowed the disease, new rust findings are still popping up. The latest findings are in commercial fields in Johnson (Sept. 21), Lanier (Sept. 20) and Terrell (Sept. 25) counties.
“The rust finds in those counties are so late I don't think yields will be hurt,” said Jost.
It's safe to say the overriding issue for Georgia's soybean yields will be the late drought. “Considering what was expected out of rust, that's an interesting development. We did a lot of talking about disease but yields, ultimately, will again come down to a well-timed rain and the environment.”
In its movement, the disease didn't act as expected. Weather patterns early through midseason were “perfect” for rust to take advantage of.
“But it didn't take hold. It's really surprising how sporadic the rust locations were. We'd find it in the southwest part of the state and then in the central. There wasn't the geographical progression we'd hoped for. If it hadn't jumped around so much, it would be easier to make predictions on movement and plan spraying.”
Asian soybean rust continues to show up in Alabama fields at low severity.
Since Sept. 9, there have been two new rust findings in the state. One was in a Clarke County sentinel plot near Jackson, about an hour north of Mobile. The second discovery was in a small commercial field in Geneva County by Slocumb.
Most of the fields in north Alabama are “yellowing up” into R-7, said Ed Sikora, Alabama Extension plant pathologist. Many fields are being harvested.
Is Sikora seeing any defoliation due to soybean rust? “The most interesting case we've had is one of the first commercial fields we found infected in Baldwin County. The grower has 50 or 60 acres he treated with Stratego about 21 days apart. He put the first fungicide on before knowing the disease was in his crop.”
Sikora visited that field earlier this month. There was very little defoliation.
“What's interesting is across the road from the main field, the producer has a 1-acre soybean patch — a different variety in the same maturity group.”
The farmer was unable to spray the patch with a fungicide. “He was aerial spraying and the patch is surrounded by power lines and trees. He left the patch as a check.”
As a result, the single acre was hit hard by rust. “Last week, it was thoroughly defoliated. That acre is a complete loss, I imagine. But right across the street, where he sprayed twice, the crop was protected from rust. That illustrates the power of a fungicide.”