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ISU holds second drought webinar

By Staff | Aug 23, 2012



FORT DODGE A statewide webinar regarding grain quality, marking options and overall concerns for harvest was held Tuesday at Iowa State University Extension offices across the state.

ISU Extension experts covered several topics regarding the possibility of diseases affecting grain, what problems may occur with handling the crop and how to prepare equipment to remain safe in the fields for soon approaching harvest.

Alison Robertson, assistant professor in ISU’s plant pathology and microbiology department, said there is a prevalence of aflatoxins and other disease issues that have been brought on by the hot and dry conditions over the summer.

Aflatoxin, Robertson said, is associated with causing various diseases in livestock, domestic animals and humans.

Aflatoxin is produced by many species, specifically aspergillus ear rot. One way to tell, Robertson said, if your corn is affected by the disease is to look for an olive-green powdery fungus that can be often seen during the drought at grain fill.

Sometimes, she added there might not be any signs at all.

“Even if an ear doesn’t have the olive-green mold, it may still have ear rot, its just not bursting out of the kernels yet, she said.

If there has been any physical damage to the kernel, such as damage caused by hail, this will also enhance the damage from the fungus.

Production of aflatoxin is greatest at 18- to 20-percent kernel moisture and the drier the kernel gets, the more aflatoxin is produced, Robertson said.

Temperatures of 77- to 95-degrees are also the greatest time for aflatoxin to be made.

There have been reports of aspergillus ear rot detected in southeast and some in southwestern parts of the state already, but so far no reports in the northern sections as of yet.

“We know aflatoxin is out there,” she said. “We know it is in southern Iowa, just no reports in northern Iowa yet.”

Unfortunately, aflatoxin is hard to sample for and is not a uniform disease that can be found throughout an entire field.

“One ear may have it and another might not,” she said. “Stressed areas of a field may have it over other parts of a field.”

One way to be prepared for the chances of your corn crop being infected by aflatoxin is to scout.

Robertson suggests scouting by checking the black layer for ear rot and looking for the olive-green mold which will be evident more at the tip of the ear. If greater than 10-percent of the ears in that field have been infected with ear rot, that field should be scheduled for an early harvest.

First before harvest, it is important, Robertson said to notify your insurance agent and to leave strips in the field while harvesting as aflatoxin can only be covered in the field and not in the bins.

She also said the adjust the combine settings to reduce grain damage, clean bins, harvest at 25-percent moisture, store the moldy grain separate from field grain and cool and dry the grain as quickly as possible.

Other potential diseases to be aware of this harvest season are charcoal rot that can occur in both corn and beans; soybean cyst nematode damage is more evident during a drought and fusarium ear rot that is also a common problem in hot and dry conditions.

Charles Hurburgh, professor-in-charge of the Iowa Grain Quality Initiative, said some of the major harvest issues producers can expect to face will be low test weights in corn below 54 pounds.

Low test weights make corn hard to handle and to store and will also; agreeing with Robertson could be infected with aflatoxin.

In many areas weak stalks and a lot of downed corn is prevalent and it is in those areas of downed corn where fungus will most likely be an issue.

2012, Hurburgh said has been a lot like the years of 1983 and 1988 with the same hot weather during grain fill. Both of those years were also notable aflatoxin years. 2005 also brought some notable numbers of aflatoxin and that year the fungus spread due to a little bit of rain and cool weather during the dry down time of the grain.

Once aflatoxin is found in a field it is to be tested, Hurburgh said by a third party person, such as the crop adjuster and once that claim is settled, the grain is property of the producer and must be documented correctly.

Hurburgh said aflatoxin levels of 20 ppb (parts per billion) up to 100 ppb can still be fed to livestock, but mainly anything above 200 ppb gets to be an issue for feeding.

Hurburgh said if aflatoxin is present that it needs to be dried immediately, with no wet holding of the grain, but to keep in mind that aflatoxin is not removed by drying and or freezing the grain it will show up all year.

Hurburgh suggests visiting www.iowagrain.org for assistance in finding labs that will test for the aflatoxin.

As far as the soybean crop, Hurburgh said producers will be harvesting one or two filled beans in a pod and those beans have a high chance of being very small, wrinkled beans with a low protein look.

They will have what has been defined as a shrinkled look to them he said.

Steve Ensley, veterinary diagnostic and production animal medicine with ISU, said the level of aflatoxins in livestock feed have been set by the FDA with 300 ppb being ok to feed to finishing beef herds in corn and peanut products; 200 ppb can be fed in corn and peanut products to finishing swine over 100 pounds; 100 ppb measured in corn products can be fed to breeding cattle, breeding swine and mature poultry while 20 ppb is the limit for feeding immature animals and is also the high limit for dairy animals, horses and pets.

Dairy cattle will be primarily affected because of the aflatoxin residue in milk, said Ensley. The FDA has a less than .5 ppb tolerance of aflatoxin in milk, but most animals will tolerate concentrations of 100 ppb or higher.

Although aflatoxins have not been a health related issue in livestock as of yet, nitrate poisoning has.

We have seen some issues with death due to nitrates, said Ensley. We need to manage them in silage, corn stalks, bales and grazing.

Ensiling (putting grass or another crop into silage) forage is the best method to decease nitrate concentration, Ensley said.

Baling corn stalks will not decrease the nitrate concentration significantly enough to matter and any grazing done in corn stalks this fall will have to be done with caution, he said.

That is usually not an issue, but it maybe some concern due to the drought, said Ensley.

The stalk of the plant and more specifically the lower third of the plant is where the majority of the nitrates are held.

If an animal is affected by nitrate poisoning, death can happen in minutes up to 24 hours and clinical signs include weakness, frequent urination and salivating.

Bov a-Pro, he said is a possible supplement to use to help decrease the effects of nitrate poisoning.

Mark Hanna, ISU Extension agricultural and biosystems engineer, spoke on adjusting the combine for poor quality grain and reducing the risk of combine and field fires.

While harvesting, Hanna recommends getting out of the combine to check what is behind you. If you are seeing a lot of grain loss left in the field, check the setting of the combine and if that is still an issue, walk out into the field to see if that could be the problem.

Most of the loss occurs at the head of the combine, said Hanna.

He also said to be sure to adjust for small corn kernel and soybean sizes.

Harvest will be happening earlier than normal, Hanna said and with drier conditions than usual as well, so producers must be prepared for that.

The greatest correlation to combine fires, which was a common issue last fall, is wind speed.

If there is enough air movement, that makes for the potential of more problems, he said.

To help prevent combine fires, Hanna said to periodically clean debris from the unit and check coolant and fuel lines to keep them clean as well.

Besides prevention, Hanna said preparation is also key. Be prepared with a fire extinguisher and have cell phones and ensure the entire crew has the 911 address to each field.

Hanna also said the ISU Extension website has links to information on how to avoid harvest fires and combine settings for drought situations.

The drought has also left some concern of the risk of herbicide carryover.

Bob Hartzler, ISU Extension weed specialist and professor of agronomy said there could be a high risk of carryover of herbicides containing atrazine, chlorimuron and imazaquin; a moderate risk of carryover with fomesafen, imazethapyr, Prowl, Treflan and HPPD inhibitors.

Herbicide carryover risks all depend, Hartzler said on the herbicide characteristic, rate applied, soil characteristics and rotational crops.

However, most herbicides, he said do not have the characteristic to carryover, even with the drought.

There may be some issues with this next year, but if you plan accordingly, there shouldnt be a real big problem, said Hartzler.

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