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Corn+Soybean Digest

Disease Guide For 2005

Diseases can blow in or blow up depending on wind, water and temperatures. The keys are to know your fields and watch the weather.

“2005 will certainly be a year of surprises,” says Martin Draper, plant pathologist from South Dakota State University. “No measure of guesswork will anticipate every problem, but if we know our fields we can have an even better idea of what to expect in the coming season.”

Adding to the list of usual suspects, plant pathologists are on the lookout for Asian soybean rust, the newest possible plague for American farmers.

Scientists from across the country have been establishing systems to warn when the deadly disease is on the move. But pathologists advise not to lose sight of reoccurring disease problems while waiting for a disaster to strike.

We asked leading plant pathologists across the Midwest what they expect your most dreaded diseases will be this year. Here's what they claim will most likely cause you the most headaches.


“The diseases to watch for on corn are northern corn leaf blight, gray leaf spot, ear rots and stalk rots. On soybeans I would watch for SCN (soybean cyst nematode), Phytophthora root rot, white mold, seedling diseases and charcoal rot. Last year we also saw a lot of SDS (sudden death syndrome), brown stem rot and stem canker; they could appear again.

“Everyone is wondering about soybean rust, which may be a minor or significant problem. We should know more about the potential risks based in part on what happens in the Deep South in April and May.”
Dean Malvick, University of Illinois


“Soybean rust is on everyone's mind. Whether it will affect Indiana this year is still a question. It depends on how early inoculum reaches the state and how favorable our weather conditions are for continued development. Some growers are considering planting soybeans earlier than normal to escape the greatest rust pressure late in the season. This is a doubtful strategy and will increase the risk of seedling blights and SDS.

“As for corn, experience in recent years shows that diseases such as gray leaf spot, northern corn leaf blight, Diplodia ear rot, anthracnose leaf blight and stalk rots are always a threat. The risk from each of these depends on weather, and also on a hybrid's degree of resistance. Growers should pay close attention to resistance ratings provided by seed companies when choosing a hybrid. If they look only at maturity, standability, yield and drydown, they may have an unpleasant surprise when severe disease develops.”
Greg Shaner, Purdue University


“If the weather is wet and cool, then we should see lots of white mold. With normal temperatures farmers should see both white mold and SDS. Normal weather is also very favorable for brown spot and other foliar diseases. If we get a cool spring, we should see SDS unless it gets dry in the summer.”
X.B. Yang, Iowa State University


“In soybeans, be on the lookout for charcoal rot, SCN and seedling diseases. As growers plant earlier in the season and there is a shift to more no-till or reduced-till acres, seedling diseases have become more common. I don't expect Asian soybean rust to have significant impact in Kansas in 2005.

“On corn, gray leaf spot and Fusarium stalk rot will be likely problems this year. I expect a return to more normal weather conditions in Kansas — hot and dry. Also, gray leaf spot is always a problem in irrigated corn acres.”
Doug Jardine, Kansas State University


“Soybean rust is on everybody's mind, but I think people really tend to forget other regularly occurring problems like SCN and the root rots. They should be planting resistant varieties to combat those diseases. Brown stem rot (BSR) could be a problem again. We saw a lot of BSR last year due to cool weather. Iron chlorosis is a big concern for growers in some parts of the state, so those growers should also plant tolerant varieties.

“As for rust, it's especially important that people stay aware of what's going on with fungicide recommendations. There are a lot of fungicides getting Section 18s so it's a fluid situation that varies state by state.”
James Kurle, University of Minnesota


“We are starting off wet, so Phytophthora and some of the early season diseases on soybeans are concerns. Of course, everybody's wondering what's going to happen with soybean rust. We'll be watching to see if we're going to have a reoccurrence of SDS, which was our biggest issue early in the season last year. SCN continues to be a problem.

“On corn, early season planting conditions, foliage diseases and stalk rots are always concerns. Last year we did have some southern rust that came into the southwestern part of the state. We'll be monitoring that situation as well.”
Laura Sweets, University of Missouri


“I'm on the lookout for more SMV (soybean mosaic virus) as we continue to see more aphids. It depends on what bean leaf beetle populations do, but I don't expect to see a lot of bean pod mottle virus this coming year. We'll have Phytophthora and stand problems if it's wet in spring. If it's drier we'll see charcoal rot. And we're all concerned about soybean rust. I think there are too many unknowns right now, but I expect to see soybean rust in Nebraska.”
Loren J. Giesler, University of Nebraska

North Dakota

“We'll always be facing the old standbys: Phytophthora root rot, white mold — if the weather conditions are favorable — and SCN. We have to watch SCN's movement. It was found in the southern part of the state just a few years ago.

“We've got some other diseases that are starting to pop up like stem canker. And last year we saw quite a bit of Septoria brown spot.

“Obviously we're going to have to keep our eyes open for soybean rust. Luckily, where we're sitting we can see what's going on to the south and get a little warning if rust is on its way. I don't know if we'll be affected this year.

“We typically don't have major problems with corn diseases. We've never found gray leaf spot. We occasionally get some common rust. Generally there are some good hybrids that do well in our conditions.
Carl Bradley, North Dakota State University


“Phytophthora root and stem rot were the big winners in 2004 for Ohio. Saturated soil conditions occurred repeatedly throughout the season and varieties with low levels of partial resistance are widely planted.

Soybean rust is currently driving much of the excitement. If this fungus is able to survive a U.S. winter and if inoculum builds up quickly in the South, this will definitely take our attention.

“On corn, northern corn leaf blight has made it back to the top of the disease list. This leaf blight, caused by a fungus, was in obscurity for 20-plus years. This disease has been managed successfully by planting varieties with resistance, but somehow these resistant genes have been lost in some of the newer varieties. Northern corn leaf blight can overwinter on old crop debris. Cool, moist conditions early in the season may get this fungus started, which could hit the plant early and cause losses. Growers' choices of varieties are critical to minimizing losses to this fungal pathogen in 2005.”
Anne Dorrance, The Ohio State University

South Dakota

“Stalk rots will likely be present to some degree. Leaf spots, such as gray leaf spot, are very dependent on moisture and residue. It's easily managed with hybrid selection. Producers who have a problem with gray leaf spot should consider that concern when making their seed purchases.

“Soybeans will have some Phytophthora and some seedling diseases, but SCN will cause losses. There are fields in South Dakota with serious SCN problems that haven't been recognized yet.

“Of course, soybean rust is the big question mark. Producers need to plan on managing the disease and hope they don't have to. As such, putting $20 in the crop budget for fungicide and application costs is in order. If you don't need it, it's like money made.”
Martin Draper, South Dakota State University


“We expect a big soybean aphid year, so soybean mosaic virus will likely increase. To date, soybean mosaic virus has not been common in commercial fields despite high soybean aphid populations in 2003. White mold is very weather dependent, but growers should always manage fields with a history of white mold as if it has the potential to develop. SCN always takes a bite out of yield despite weather patterns.

“On corn, gray leaf spot and anthracnose have established a consistent track record in the southern half of Wisconsin. Eyespot tends to be most prevalent north of Madison.”
Craig Grau, University of Wisconsin

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