LOUISVILLE, Ky. – The only thing researchers and farmers pooling their brainpower at the National Soybean Rust Symposium in Louisville in mid-December could agree upon about controlling Asian Soybean Rust (ASR) was that there is no one way to control it … because it still can’t be fully predicted or easily scouted.</p><p>
“Rust is difficult to identify,” said John Damicone, Oklahoma State University extension plant pathologist – which, incidentally, is one other sentiment all the speakers could agree upon. “We have septoria (brown spot) everywhere in the state,” which he said could be mistaken for ASR by the inexperienced. “You go batty looking for rust out in the field.”</p><p>
Kevin Black, a technical support specialist with Growmark – a cooperative covering Iowa, Illinois and Wisconsin – trains others to work with growers and agreed that ASR is tricky. “This thing is going to be a nightmare to identify, for the average individual,” he said.
Neither Oklahoma nor Texas is a big soybean-producing state. </p><p>Oklahoma only harvested 170,000 acres this year, and Texas, 80,000, compared to a smaller state like Iowa, which harvested 8.5 million acres. For that reason, despite being closer to the biggest incidences of ASR in the United States, neither state has a lot of resources devoted to scouting or dealing with the fungus.</p><p>
“I didn’t really know what to say to farmers,” Damicone admitted, when ASR was found in Oklahoma in July. “We didn’t have any fungicidal data.” He added he had done some tests with fungicide for three years, but saw no yield changes that might provide a clue.
The current sentinel and monitoring system in place in Oklahoma is not sustainable, he explained – it’s too labor-intensive and the money’s going to run out. It may be important to shore up, though, since with predictions as high as $15 soybean futures next year, he predicts more local farmers may jump on that bandwagon.
Damicone added that “contrary to popular opinion, Oklahoma is not a desert wasteland” – in fact, this year the central region of the state received 20 inches more than normal seasonal rainfall, and conditions were ripe for ASR to settle in soybean fields.</p><p>
Ken Dalenberg, a farmer near Champaign, Ill., and a United Soybean Board director, agreed more sentinel plots south of the “soybean belt” in the U.S. would be welcome. Unlike Oklahoma, Illinois has many sentinel plots and scouting provides good early detection – four sites were confirmed in 2007, and even more “mobile sentinel” plots were tested after the first find. Dalenberg believes more southern plots might give better warning to northern farmers of impending disease.</p><p>
In Illinois and elsewhere, he would like to see the ASR sentinel plots kept permanent to scout for other diseases, as well.</p><p>
One grower who actually contended with ASR in 2005 is Billy Wayne Sellers of Baxley, Ga., also president of the Georgia Soybean Assoc. and Chair of the Georgia Agricultural Commodities Commission for Soybeans. In Georgia, cotton is king and soybeans are sparse, at only 265,000 acres harvested this year, though Sellers believes this could change in 2008 because of higher soybean futures.</p><p>
Historically, soybean growers in his area have been more worried about nematodes and insects, than diseases. In 2005, he cooperated with the University of Georgia by spraying part of his crop with fungicide at the R2 and R3 stages just in case ASR hit that season, so researchers could compare the untreated areas. He was well familiar with the chemicals, having sprayed his peanuts with fungicide for years, and spraying for fungus in the warm, humid Southeast isn’t uncommon.</p><p>
At around stage R5, the rust showed up. Sellers said thanks to the fungicide, those plants produced eight to 18 more bushels/acre than damaged plants, and that more expensive chemicals really have worked better for him.</p><p>
“Don’t really skimp unless you want to take a chance on not making quite as much (yield),” he said, adding if ASR sets in close to the end of a soybean plant’s life cycle, however, cheaper fungicides may work as well.</p><p>
He advises other Georgia farmers to closely monitor their fields and to spray at even the smallest sign of confirmed ASR, rather than waiting two weeks to see if it’s progressed.</p><p>
“We have that mentality,” he half-joked. “You go back (after that long) and it’s all pustules, it’s all over but the crying.”</p><p>
Citing a UG cost study, he said depending on what fungicide a grower decides to use, they will need to see anywhere from a 1.3 to 2.5 bu./acre increase to justify the expense of purchase and application.</p><p>
He said one unique consideration for some Southern farmers is hurricane season. He lives seven miles from the Atlantic Ocean and if a fungicide keeps his crop green and leafy for an extra two to three weeks, that’s that much longer a storm has to potentially make landfall and destroy it.</p><p>
Blaine Viator, a plant pathologist and 18-year certified crop consultant in southern Louisiana, has a background mainly in sugar cane. But with higher prices, more farmers are eyeing soybeans and the land is suited: it hasn’t supported soybeans in several years, so there’s not disease to over-winter in the soil, and there are good growing conditions.</p><p>
But he agreed with Sellers about fungus problems, describing his area – which receives 60-70 inches of rain annually and is hot – as a “fungal petri dish.” He added aerial spraying seems to work well and that generally, “compared to our other diseases, rust is not very difficult to control if you get it in time” – a familiar refrain by many at the Louisville conference.</p><p>
Even he, however, has healthy respect for the disease, especially after he’s wrestled with it at the R6-R7 stages … and in hot, dry weather, a condition in which it’s not supposed to flourish. “Every time we think we know the facts, it comes up and surprises us,” he said, adding this is why Louisiana growers tend to spray fungicides twice as a matter of course.</p><p>