Much of the corn looks very good, however ear rots have been a concern to some area farmers as the crop comes out. Ear rots can present a number of problems, from the potential presence of toxins in the grain, to quality, to low test weight, to serious storage issues. Environmental conditions and heavy insect pressure this year conspired to produce a lot of exposed, damaged ears. These are predisposing factors for ear rot infection. Late season rains have also presented an ideal environment for continued deterioration of the grain by fungal rots.

Because of the ear rot fungi already present on the grain, seed moisture of 18-20 percent or more will set the stage for problems in storage. When ear rot fungi continue growing on stored grain they produce moisture and heat needed for infection by a progression storage fungi. To reduce potential problems from storage fungi, store grain in thoroughly cleaned debris free bins. Store grain at moisture levels of 13-18 percent. Proper aeration is important to prevent the build up of moisture pockets as well.

Although there are many fungal ear rots, infection by Aspergillus is typically one of the most frequent concerns when ear rots are a problem. The concern is real because Aspergillus fungi can produce very potent toxin called aflatoxin. Aflatoxin is just one member of a larger group of chemicals called mycotoxins, which are toxins produced by fungi. Aflatoxins are some of the most potent carcinogens on earth so that gets everyone's attention. The allowable amount of this toxin in grain for food or feed is highly regulated.

Aflatoxin can be produced by the fungi Aspergillus flavus and A. parasiticus. These fungi are present everywhere in soils and organic matter. Stored grain can be infected by the fungi or they can infect in the field. This typically occurs when the weather is dry and hot (more than 86°F) during silking to late kernel development. We saw this happen in 1988 and it may happen again this year, certainly for some of the drought stricken areas of the state.

Aflatoxin produced by A. flavus is most likely to be produced in the field and particularly in storage after the kernels have been damaged by insects, birds, mites, hail, early frost, heat and drought stress, windstorms and other unfavorable weather conditions. The presence of the fungus A. flavus in a feed sample does not imply that the feed is unwholesome or that it will contain high levels of aflatoxin. Testing is necessary to determine how much toxin may have been produced.

Sampling grain for aflatoxin at the elevator follows established federal protocols. A 10-pound sample is usually collected by pooling 5 or more probes collected from an auger discharge of one or more combine hopper loads. The sample is ground for analysis. There are 3 methods of aflatoxin analysis. One is a visual examination called a black light test. A second type is a quick qualitative laboratory immunoassay procedure for the presence of the toxin; the quick tests now also have quantitative test kits for a range of toxin levels. And third are a number of laboratory tests for the actual quantification of the toxin.

If you think your corn may have been at risk what can you do to minimize chance of fungi and toxin development now or in storage? First, harvest drought-stressed and insect-infested grain at early maturity as soon as the moisture content allows minimum grain damage: for shelled corn (23 to 25 percent moisture), ear corn (25 to 30 percent). Set the blower on the combine high. Adjust the combine header speed to minimize cracking and reduce the content of trash, fines, and small broken or mold-infected kernels, especially those kernels near the tips where mold infestation is most likely to be present. Upward of 50 percent reduction in existing aflatoxin levels (or below 20 ppb) can be achieved in some fields by careful monitoring of combine cylinder, screen and air flow levels.

Drying is then essential. You need to prevent further growth. Dry all grain to at least 13- to 14-percent moisture as rapidly as possible, not to exceed a 24 to 48-hour period after harvest to prevent production of aflatoxins.

Safe, long-term storage can be accomplished at a uniform moisture level of 13 percent or somewhat below. Moisture may be 14 percent if grain is to be moved or sold in a shorter period of time. For slow drying, the grain should contain no more than 18 to 20 percent moisture in full-bin drying; this may not be the best method when toxins are a concern. Another possibility is high-temperature drying until the grain reaches 18 to 20 percent moisture, followed by low-heat drying to13 percent moisture. Avoid air drying of mold-damaged corn without heat. Research has shown aflatoxin increases of 100 to more than 2000 ppb in three days when recently harvested field corn was stored at high moisture levels. Delays in transit to the storage bin or buying point need to be minimal. Aflatoxins have been shown to increase in truckloads of contaminated corn by as much as 6 percent per hour of delay. Cool the grain after drying and maintain dry storage conditions. When possible, continue cooling until the grain temperature reaches 35° to 40°F. Thoroughly screen and clean the grain and all bins before storage to remove dirt, dust, and other foreign matter, crop debris, chaff, and cracked or broken seeds and kernels. Most of the contaminated corn is in the small and broken kernels, which will drop through a screen. Store the grain in water, insect, and rodent tight structures. Continue periodic aeration and probing for hot spots at intervals of 1 to 4 weeks throughout the storage period.

And finally, if you have crop insurance, remember that the crop is insured while it's in the field. If you think you have a 'very' suspect field, harvest a pass and have it tested. Once you harvest the field it's all yours and not the concern of the insurer. Stay safe as harvest continues.