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Purdue: Be on the lookout for fungus degrading corn

By LINDA McGURK
Indiana Correspondent

WEST LAFAYETTE, Ind. — The cool, wet fall weather in large pockets of the Midwest didn’t just keep farmers out of the fields for weeks. The combination of moisture during silking time and the delayed harvest has made a perfect storm for mold in the crops, and according to the Purdue University extension service, the problem is widespread in Indiana.

“If you haven’t scouted your fields yet, now is a good time to do it,” said Charles Woloshuk, a Purdue University plant pathologist, during a Nov. 9 conference call addressing ear rots. “What we’re seeing pre-harvest is that ear rots seem to be a major problem this year.”

Out of four major ear rots common to Indiana, Gibberella and Diplodia are the two causing farmers the most headaches this year. Gibberella tends to be more prevalent in the northern part of the state, and can be identified by pulling the husks down and checking for a pinkish or reddish mold that starts at the top of the ear and develops towards the base.

Diplodia, on the other hand, is found primarily across the southern part of the state and is characterized by bleached husks with tiny black specks. The whitish or grayish Diplodia mold usually starts at the base of the ear and sometimes makes the cob appear rotten.
Gibberella produces two mycotoxins – deoxynivalenol (DON, vomitoxin) and zearalenone – that are causing big losses for some livestock producers who started feeding their animals moldy corn from this year’s crop.

In hogs, deoxynivalenol quantities as low as 3-5 parts per million (ppm) during gestation can cause low fetal weights, and the pathogen can cause vomiting and reduced feed intake at levels of 5-10 ppm. At levels above 10 ppm, the pathogen can lead to complete feed refusal in hogs.

The other mycotoxin, zearalenone, primarily impacts breeding herds, as replacement gilts may not cycle and the sows could have trouble getting bred at levels above 3-5 ppm.

“Hogs are the most sensitive (to moldy grains), and right now hog producers are having issues. If you’re using it for breeding animals you need to be very careful,” Woloshuk advised. “Cattle can take quite a bit (of mold), but you shouldn’t feed a lot of moldy feed to your animals; it’s just not right.”

Todd Applegate, a Purdue extension poultry specialist, said they are less sensitive to the mycotoxins than hogs, though there are reasons to be careful about feeding the birds moldy grains.
“DON or vomitoxin is known to suppress the immune system in poultry, making them more susceptible to sickness. Levels of DON known to have these effects begin to occur at about 7.5 parts per million, or less,” he said.

Purdue urges farmers to harvest potentially infected fields as soon as possible and recommends they test their crop for mycotoxin levels. Brian Richert, an extension swine specialist, said some producers have started feeding new crop corn and had nearly 100 percent feed refusal because of the high vomitoxin levels in it.
“Those producers had to suck all that feed back out of the feeders, find a source of new feed and try to get feed back in for those animals,” he said. “It can cause some significant problems if producers don’t test their corn up front.”

“If you see any levels of disease, store the grain separately,” Woloshuk said, adding that farmers should dry the affected corn immediately. “Below 20 percent moisture the pathogen will stop growth and mycotoxin production, but you need to get it down to 14.5 percent for safe storage. It’s very important that you don’t delay drying, or you risk getting storage mold.”

Richard Stroshine, another Purdue professor, advised farmers who have moldy corn to remove as much of the fine material or broken pieces as possible.

“Mold can more easily grow on broken kernels because this is the food source for the fungi and it is more readily available,” he said in a statement from the U.S. Grains Council. “They also impede airflow during aeration of stored corn. So, getting rid of the fine material is a good strategy for improving grain storage, especially this year.”

Though ear rots are caused by weather and typically aren’t a big problem in Indiana, Woloshuk said farmers should take precautions to protect themselves against a repeat of the disease going into next year.

“Think about tillage to make sure the (plant) materials degrade. Rotating out of corn will encourage degradation of residue, but if you have to go into corn, pay close attention to the hybrids,” he said. “You may want to go out of corn for two years to make sure you get rid of the disease. If you go back after one year, pick hybrids that are resistant to Gibberella.”

Help from Illinois
University of Illinois specialists are scheduled to answer farmers’ questions and concerns about the presence of yeast, molds and mycotoxins in corn in two “webinars.” The first is today from noon to 1 p.m. CST. To register, visit
www1.gotomeeting.com/register/169847248
Once registered you will receive an e-mail confirming your registration with information you need to join the webinar. Computer requirements include:

•PC-based viewers: Windows 2000, XP Home, XP Pro, 2003 Server, Vista

•Macintosh-based viewers: Mac OS X 10.4 (Tiger) or newer

Topics to be covered include status of wet molds and mycotoxin formation; update of mycotoxin levels measured in commercial labs; storage alternatives, including drying, high moisture corn, and use of propionic acid; pricing wet corn; feed value of immature corn for livestock; mycotoxin binder choices; and any other questions from participants.

Another session is scheduled for Dec. 3, at the same time. Visit www1.goto meeting.com/register/842673729 to register for that session.

11/18/2009