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Mississippi dealing with blight, Arkansas with rust

STARKVILLE, Miss. – As corn harvest kicks off, the widespread occurrence of northern and southern leaf blight continues to be the big story in Mississippi.

“Blight was promoted by the wet conditions during June,” says Erick Larson, the state’s Extension corn specialist. “It infected our crop during mid-June, causing leaf lesions and death. That hastened the infected crop’s maturity.”

Larson said the blight shuts down the photosynthetic capacity of the plants. That, in turn, causes yield losses because the seeds don’t fill out to their full potential. “We’re seeing significant yield losses in some of those fields – as much as 30 percent (40 to 50 bushels per acre).”

To the west, Arkansas’ corn has its own problem: rust. “I’m in Lee County (in east Arkansas) looking at corn fields,” says Jason Kelley, Extension corn specialist. “Corn here, as well as in the rest of the state, is really showing the end results of rust. Leaves are very desiccated. I just came out of a field of hybrids that didn’t have much rust resistance. The rust was all the way to the plant tops. These plants dried down a lot quicker than they should have. I’m seeing this same thing all over the state.”

Kelley says it appears that when kernels were mostly filled, rust robbed the plants of their “greenness.” That meant the plants had to cannibalize their own stalks in order to finish filling out the grain. “Very, very weak stalks” resulted.

“From the road, the crop looks fine,” says Kelley. “When you go out in the field, though, you can see there’s a real issue. You can barely push on a stalk, and they fall over. If we get a storm of any kind – especially a wind storm – a whole bunch of our acres will be on the ground.”

Mississippi is seeing much the same due to blight. “Our stalks are very weak and if a storm blows through, lodging could occur,” says Larson. “Fear of that will lead some of our farmers to harvest at between 20 percent and 25 percent moisture. We’ve already had some fields being harvested as early as July 20.”

The worst blight-affected fields in Mississippi are corn following corn. That’s because the blights will over-winter on corn residue or trash.

However, Larson is also seeing severe infections in first year corn fields with susceptible hybrids. That’s particularly true in some hot spot areas of the state. These hot spots have a history of large corn acreage – Noxubee County, Hollandale and Glendora, as well as some areas of Yazoo County and around Vicksburg.

“Most of the moistures currently are in the lower 20s to around 30 percent,” says Larson. “We’re probably around 10 percent harvested. We’re getting started in the Delta just now and haven’t made a whole lot of progress in east Mississippi yet.”

With warmer weather and fewer rain events, Louisiana’s corn is finally getting a chance to begin the “dry down process,” says David Lanclos, Extension corn specialist. While the crop has experienced more problems than is usual, Lanclos remains “relatively optimistic about yield potential. I still do not think that we will have much more than about a 10 percent to 15 percent loss.”

Lanclos says Louisiana’s latest problems involve running “morningglories and rotting of some portions of the ear. Because of all the rainfall, some husks have been loosened to the point where moisture on the end of the ear rotted some kernels.”

The several inches of lost ear can add up very quickly, he says. “The worst part is there’s nothing we can do about it.”

In Arkansas, Kelley says rust normally comes into the state’s crop after grain is filled and doesn’t make much of an impact. “This year, the disease came in a little earlier – although not early enough to stop grain filling, luckily. The weather conditions were right for rust and there’s plenty of corn in neighboring states. Wind picks up diseases there and blows them right to us.”

There’s nothing that can be done to remedy the situation, says Kelley. Producers with the aforementioned symptoms need to harvest as early as they can.

“They may need to harvest at a slightly high moisture level – hopefully, they’ve got a grain dryer. Otherwise, it’s a choice between dockage and risking a storm blowing their crop over. We should begin harvest in earnest anytime (during the second week of August). I’ve heard some combines are running here and there but I haven’t seen a harvested field yet.”

In Tennessee, corn has also had more widespread rust problems than is normal. “In the past, we saw rust mostly in isolated areas,” says Angela Thompson, Extension corn specialist. “I’m not as concerned about corn planted in March and early April. Those crops were well into black layer when the rust hit. I’m far more worried about our later-planted corn.”

Still, says Thompson, Tennessee’s yield potential is good – especially for the earlier crop.

“I haven’t heard of anyone harvesting yet but we’re very close – especially in the southwest corner,” she says.

Regarding rust, Kelley says there are “definite differences” amongst hybrids. Some plants have rust all the way to the top and the whole plant is, “just inundated. In other hybrids, rust isn’t nearly that bad. Yield-wise, I don’t think rust will hurt us too badly. Test weights in the worst fields may be a little lighter than usual but, barring a windstorm, we’re still expecting a good harvest. Our state record is 145 bushels per acre. We should be around the 140-bushel range.”


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