Monitor Stored & Standing Corn for Grain Mold Diseases

Monitor Stored & Standing Corn for Grain Mold Diseases

March 5, 2010

Just because your corn may be out of the field doesn’t mean it’s “out of the woods,” so to speak.

Corn is still vulnerable to grain molds that develop during storage from the ear rot diseases that occurred in summer and fall of 2009. Producers can expect the fungi to continue to grow in the bins, storage piles, etc. when the temperatures increase above freezing, particularly if the grain moisture is greater than 15%. (The higher the moisture, the greater the potential problem.) These diseases can cause even greater losses in grain quality post-harvest during storage than they did prior to the fall harvest.
Large pile of discolored grain
Figure 1. Corn stored outdoors in piles has been exposed to winter precipitation that may result in the development of grain molds and a reduction in quality. (Source: Larry Ziems)

Snow drifts in standing corn

Snow drifts in standing corn

Figures 2 (top) and 3 (directly above). Standing corn left in the field from the 2009 crop is still at risk for ear rots and grain molds and should be evaluated for damage prior to harvest. (Source: Larry Ziems)
Fusarium ear rot on corn
Figure 4. Fusarium (top) and Cladosporium (below) are two of several ear rot diseases that occurred in Nebraska corn last fall. Most fungi causing ear rot diseases can continue to grow in bins during storage, causing grain molds and reducing grain quality.Corn ear rot

Cold winter temperatures helped to slow or temporarily stop grain mold development. However, they did not kill the fungi causing grain molds, which will likely continue to grow in the bins and other storage areas once temperatures increase above freezing.

Outdoor storage piles of corn (Figure 1) that have been exposed to winter precipitation and other changing climatic conditions over the last few months may be at increased risk for molds and decaying conditions and damage or decay may be visible on the surface or in the middle of piles. It is important to continue to monitor the condition of stored corn throughout its storage period, particularly for the development of mold growth. During the last two weeks, some people have already observed the decline in grain quality and development of a moldy “crust” on the surface of bin-stored corn in some areas.

Standing Corn

In contrast, a considerable number of acres of the 2009 corn crop has not yet been harvested, particularly in western and northern Nebraska, where grain moistures remained too high for harvesting throughout the fall. Harvest will be further delayed in some areas as deep snow drifts (Figures 2 & 3) have formed in the field and will require significant melting before harvest can occur. The quality of lodged corn that is in contact with the soil or trapped by snow may have been further compromised, as well, and should be evaluated prior to harvest so that it can be handled and utilized appropriately.

Some ear rot diseases that developed in 2009 were visible (Figure 4), while others were not. In either case most of the fungi causing them will continue to grow in sub-optimal storage conditions. Corn harvested from fields with a history of these ear rot diseases should be considered more perishable and used or marketed quickly to avoid further losses.

For more information about common ear rot diseases reported in Nebraska in 2009 see

Potential for Mycotoxin Contamination

Some ear rot diseases are caused by fungi that can produce toxic secondary metabolites called mycotoxins. Probably the best known and most notorious mycotoxin is aflatoxin. We are NOT concerned about aflatoxin contamination in the 2009 Nebraska corn crop because growing conditions were not conducive for the ear rot diseases caused by the fungi Aspergillus spp., which produce aflatoxin. Those diseases tend to develop during hot, dry growing seasons.

In contrast, the cool, damp conditions of 2009 strongly favored other diseases, such as Fusarium and Diplodia ear rot, which were more common last year. The Fusarium spp. that cause these diseases can produce other mycotoxins, such as fumonisin and vomitoxin (DON). Although we do not have evidence to believe there is a serious mycotoxin problem in the 2009 crop, the potential is there considering the increased incidence and severity of ear rot diseases.

Mycotoxins can have serious negative effects on some livestock (please link to some of Mike Carlson and swine specialist materials). In particular, fumonisins can be especially toxic to swine and you should use caution when feeding contaminated corn. Other species, such as cattle, are more tolerant of fumonisins so feedlots are likely good outlets to use contaminated grain from 2009.

For more information on feeding this corn see

Related Health Hazards

At the very least, moldy corn can present other hazards in the bin that you should be aware of. People who have compromised immune systems or who are prone to respiratory illnesses should be especially cautious when working around or handling molding grain. They should protect themselves by wearing dust masks and gloves.

Fungal spores can act as particulate matter and may be concentrated in less ventilated areas, such as grain bins. Other safety precautions should be considered when working in filled bins and collecting samples to avoid entrapment. See these articles from Purdue University for safety tips for working in grain bins:


For more information on grain drying and related topics, see

Tamra Jackson
Extension Plant Pathologist