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Corn hybrids, aflatoxin research

In front of an impressive field of corn plants, Rick Mascagni paces powder-dry silt loam and addresses four trailers full of field day folk. With the region having turned from very wet to very dry, the large, late-planted corn hybrid test at the Northeast Research Station outside St. Joe, La., is a good place to check out how the corn crop is doing in mid-June.

“This spring we’ve had a couple of issues with farmers planting corn in the early- to mid-March window,” says the LSU AgCenter research agronomist. “There was a lot of rain, cold weather and erratic stands. Many had to replant.”

With 89 hybrids, the corn test was first planted on March 23 and subsequently had a terrible stand.

“Some of the hybrids have not silked out yet (June 17). It’s going to be interesting if a couple of these hybrids show some tolerance to drought conditions. The last rain of an inch or higher was 1.6 inches on May 3. It is extremely dry.

“Normally, when you plant corn later it produces a taller plant with a smaller stalk. As you look at this crop — particularly in the sandier areas of the field — it isn’t very tall. I think that’s partly due to the dry weather.”

Only four of the 89 hybrids in the test aren’t Roundup Ready.

“At each planting, we applied 0.12 pound active per acre of Aztec. We wanted to make sure all the hybrids are on an equal basis on insect control, particularly in case of rootworm.”

Mascagni and colleagues also put out 200 pounds of nitrogen around the two-leaf stage for the first planting. Just to be on the safe side, another 50 pounds of nitrogen was applied at the two-leaf stage of the second planting.

“There are still some (shaky) spots, but overall the second planting produced a much better stand.

“We planted this with a cane planter because of the high number of hybrids. It’s notorious for (placing) two or three plants together and then a skip. I don’t like that, at all. Overall, we’ve got relatively good spacing in this test.”

Mascagni hopes the test “gets some rain, number one. Also, I hope we get some good information on this late planting date. We’ve got a couple of other tests on the station that were planted mid-April. I know a lot of farmers are interested.”


If dry weather remains, one problem farmers may face is aflatoxin. Ken Damann with the LSU Department of Plant Pathology and Crop Physiology has been doing aflatoxin work for several years.

With Mascagni’s cooperation, one of the things Damann reinstituted this year was aflatoxin testing of hybrids.

“If this hot, dry weather continues, we’ll probably be facing some aflatoxin issues,” says Damann. “To give you an idea of which hybrids do better in those conditions, over at the Macon Ridge station, Rick has this test replicated and has provided the 89 hybrids for me to go in and inoculate.”

About 20 days after mid-silk, “we’ll go in with a bottle of inoculum, dip a vaccination device into the inoculum and plunge it into the ear. We’ll do that on a number of the hybrids, let them mature, hand-harvest, shell the ears, grind up all the corn and then analyze it for the aflatoxin levels. We’ll then provide a ranking of the most sensitive (varieties) to infection and aflatoxin and which are best. This information will be on the Web when Rick puts out the yield data. That should be available to you for next year’s crop.”

Damann is also working on a biocontrol approach for aflatoxin. One of the ways researchers hope to eventually control aflatoxin contamination is to apply non-toxigenic isolates in the fields. These outcompete toxigenic isolates and suppress aflatoxin contamination.

In 2007, Damann and colleagues sampled from 11 different fields “up the Mississippi River, west of Baton Rouge and in the Red River area — all corn-growing areas. Soil samples and kernel samples were gathered. We got 600 isolates from kernels and 300 from soil.”

Each of the isolates was placed in a rice medium to determine aflatoxin production. The first thing Damann found is there are many more non-toxigenic isolates from the kernel isolates than from the soil isolates.

“The ‘hottest’ 11 isolates — one from each location — were picked. Those were then challenged with the non-toxin-producing isolates.

“Our philosophy has always been to go to the kernel and isolate the non-toxin producers so we know a (particular) isolate has the ability to get into corn and infect. If they get into corn and infect and aren’t a toxin-producer it causes no problem. Ear rot isn’t a problem — aflatoxin is. So, if they don’t produce (aflatoxin), we don’t care if the ear is infected.”

Researchers want to select non-toxigenic isolates that compete with toxigenic. “But when we tested the 11 hot ones against soil non-toxigenic and kernel non-toxigenic, the best competitors that inhibited toxin production were from the soil isolates.

“We’ve got four isolates from soil titled 17, 19, 21 and 22. All four are being tested in the field (behind me), the field at Macon Ridge and a field at Ben Hur in Baton Rouge.”

The non-toxigenic isolates are applied to sterile wheat seed and then spread through the field prior to silking. That allows the “fungus to grow on the wheat seed and produce spores that fly around and land on the silks. They get into the corn and outcompete the toxigenic isolates.

“A group in Georgia has commercialized — primarily for peanut biocontrol isolates but also for corn — an isolate called ‘Afla-guard.’ We’re also going head-to-head with Afla-guard, which is also in the trials. Next year, we’ll be able to tell you which of our four is best and how they stack up against the commercially-available Afla-guard.”


TAGS: Corn
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