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9/7/2009 - 9/13/2009

Quality Issues Related to Hail Damaged Crops

By Charles R. Hurburgh, Department of Ag and Biosystems Engineering; Alison Robertson and Gary Munkvold, Department of Plant Pathology

The August 23 hailstorm across north central Iowa, and to a lesser extent the earlier northeast Iowa storm, caught crops approaching maturity. The sheer size of the north central event, almost 200 miles long and 10 miles wide, assures that damaged grain will reach the market.  Fortunately, weather since the storm has been very favorable for hastening maturity and minimizing mold toxin potential. 

Corn maturity in general was lagging across the state, anywhere from 200 to 500 heat units below normal. A relatively high moisture harvest seems inevitable, even without the hail concerns. However, the recent weather – mid 70s and low 80s during the day and 60s at night – has brought corn toward maturity faster than the late season conditions of 2008. This means that, even if the harvest starts out wetter, it may dry down faster because of more complete maturity. This will also increase test weights, storage stability and handling properties over the problem crop of 2008.

Corn in the intense central band of the hailstorm was killed by the hail; the hail stones were large enough to cause extensive bruising. The bruised kernels will shrivel; many will be moldy but many also will pass out the back of the combine. Corn that has had its development stopped with the milk line partway down the kernel will be soft, have free sugars and be very low test weight (below 50 pounds per bushel, some down to 40 pounds per bushel). This corn will not dry easily but the recent warm weather will start the drying process right away, without creating toxin problems. Cool wet weather would have increased the risk of vomitoxin and fumonisin; hot weather would have increased the risk of aflatoxin. Mold will be present, but with less likelihood of toxin production. Feed users should spot check initial harvest just to be sure. Your veterinarian can assist in making decisions; the Iowa State University Veterinary Diagnostic Lab provides toxin testing. 

 Stalk strength will be poor in hail damaged fields. It may be worthwhile to harvest remaining crop, putting only a few feet of corn in bins and using advantage of the dry air. The key is to get the moisture down as quickly as possible to slow both cob and kernel molding. Do not expect the test weight of very light corn to increase after drying. Elevators will isolate, dry and move this corn rapidly. Expect discounts for moisture, damage, test weight and possibly foreign material.

Corn in the larger hail area outside the high intensity band had shredded leaves, with some bruised stalks and ears from larger stones – likely resulting in less than 10 percent damaged kernels by grading standards. Test weights will be reduced (50-54 pounds per bushel) and field drydown may be slower, but test weights should increase after drying. Again the present weather is a big help. This corn will present the most difficulty for the market because it will not be distinctly low quality, but may require the buyer to grade for both damage and test weight.  This is difficult at harvest; buyers may choose to accumulate composite samples by seller, and grade those, or they may visually grade and price each load. Test weight is measured automatically by the moisture meter. 

Damage grading is sometimes controversial because visual evaluation is required; graders should use color copies of the official damage designation photos as a comparison reference.  This year is particularly difficult for damage because of the problems still on hand from the 2008 crop. The grain market has little leeway to handle damage from 2009. Ethanol plants are negatively affected by damage; fermentation reactions are retarded. As always, test weight is a good way of making a rough division of corn quality and storability.

types of mold on corn

Hail damaged ears with signs and symptoms of Gibberella ear rot, Fusarium ear rot, Penicillium ear rot and sooty mold. (Robertson, 2009)


Barring frost, the primary soybean quality issue for beans remaining attached to plants will be smaller seed size (down to chips in some cases). Percentagewise, there were greater yield losses in soybeans than corn. The impact on composition (percentage protein and oil) is uncertain because the total yield and the quantities of individual nutrients were both reduced. The smaller beans and chips will be harder to process; many very small pieces will be removed by the combine. Small beans or chips will not be graded damaged unless discolored as well.  They are not foreign material unless they pass through the 8/64 foreign material sieve. They are not splits even if they pass through the splits sieve because splits must be physically broken pieces. However, the bruised plants will create more FM in the tank, due to broken stems.

Beans in pods that were bruised but not removed may be discolored. As with corn, comparison to standard color photos is needed to identify damaged soybeans in the grades.

General Recommendations
Iowa was headed for a wetter than normal 2009 crop before of the hailstorms. Late August and early September weather has been ideal for accelerating the lagging maturity and reducing the high moisture potential. Nonetheless, expect to dry corn again this fall. Even air and low temperature dryers, if only filled one-third or less depth will operate rapidly in present conditions.  Take advantage of this if you have lodging; soybeans too will dry easily in 70-80F weather.  Soybean moisture probably will fall rapidly in the field after leaves have dropped, making drying less necessary. 

There is carryover of 2008 crop on hand, primarily in elevators but some on farms. Do not mix 2008 and 2009 crops in the same storage. The old corn will have a high tendency to spoil; its storage life is probably expended or nearly so. Mixing with less moisture stable new crop creates an unpredictable situation.

Temperature control is critical. The same warm weather that is helping maturity will mean warm grain coming from the field. It must be cooled immediately, even if drying is not necessary. Leaving grain warm after harvest can remove months of storage life in the next spring and summer. Good aeration practice is to immediately cool harvested grain, then cyclically reduce temperatures into the 30s as the outside air temperature falls. Remember that once a cooling cycle is started, it should not be stopped until complete. The benefits of having a bin temperature monitoring system becomes very clear during aeration cycles, as it tracks cooling progress without over aerating.

Remove center cores of bins to take out fines and trash. Larger bins (over 50,000 bushel) may have to be cored twice. Level the grain after the last coring. A vac can be used to core piles or flat storages, although it has less effectiveness and removes more grain than bottom center draw off.

Expect ethanol plants and other users to become increasingly careful about grading inbound corn. Damage and test weight discount scales are going up. The steady increase in production (yield) has come with some cost in wetter corn, less high quality storage as a percent of total, and more management issues. Plan ahead very carefully which grain should go in which storage area, based on expected length of storage time. The better corn (higher test weights) should be the corn held for longer periods, in the better storages. Move lighter corn to market as soon as possible.



Charles Hurburgh is a professor of Agricultural and Biosystems . He can be contacted at (515) 294- or by email at Alison Robertson is an assistant professor of plant pathology with research and extension responsibilities in field crop diseases. Robertson may be reached at (515) 294-6708 or by email at Gary Munkvold is an associate professor of plant pathology and seed science endowed chair in the Iowa State University Seed Science Center with research and teaching responsibilities in seed pathology. He can be reached at (515) 294-7560 or by email at

CCA Credit Opportunity at Precision Agriculture EXPO

By Jim Fawcett, Extension field agronomist

Certified crop advisors can earn up to five hours of credit (including 2.5 hours in soil and water) by attending a 9 a.m. special session on Thursday, Sept. 17 on “Strip Till Using Precision Ag.” This session will be followed by the Advances in Precision Ag EXPO; both will be held at the Iowa State University Southeast Iowa Research and Demonstration Farm near Crawfordsville.  The EXPO, from 10:30 a.m. to 4:30 p.m., will feature field demonstrations and many exhibits by the industry’s leading precision ag companies.

The CCA session in the morning will include hands-on experience in properly setting tillage and planter equipment to achieve the best results. At noon Dave Nelson with Brokaw Supply will present “Operation Strip Till with RTK Guidance Systems,” followed by Dr. Matt Darr, ISU ag engineer on “Precision Ag – Where We’ve Been and Where We’re Going.”  Field demonstrations at the EXPO will include strip tilling and planting on the contour using RTK guidance, auto-shutoff planters, and auto-steer. People will have the opportunity to ride in the equipment and see first-hand how it works.

The credit fee is $50 for CCAs (or $15 for no credit). The EXPO is free to Southeast Iowa Research Association members and $15 for non-members.  Attendees also have the option of purchasing a 5-year association membership for $25. The entrance fee includes lunch. The farm is located 2 miles south of Crawfordsville on Hwy 218, then 2 miles east on County Road G-62, then 1 mile north. All field days are open to the public; the EXPO and CCA session will be held rain or shine. To pre-register for the CCA session, please call the Johnson County extension office at 319-337-2145 or send Jim Fawcett, ISU Extension field agronomist an email at

September 7 Crop and Weather Report

By Doug Cooper, Extension Communications and External Relations

This week’s interview is with Charles Hurburgh, Iowa State University professor of agriculture and biosystems engineering. He talks about the issues that farmers face this harvest season. He says they can expect a huge corn and soybean harvest, but some parts of the state may face quality issues. In general, producers will be dealing with high moisture corn at harvest and some corn won’t make maturity.

Many issues will be a repeat of last year – low test weight and storability issues along with high moisture corn. Hurburgh talks about a lot of last year’s wet corn hanging around waiting for new corn, and where to put this year’s high moisture corn becoming an issue.

He says the next two to three weeks will play a significant role in the development of mold and toxins in corn fields that have hail damage this summer. Hurburgh talks about the need for good scouting in these fields to determine the amount of ear bruising and stalk health, and the importance of testing for toxins.

Elwynn Taylor is traveling this week.

Degree Days - Will it be Septembrrrrrr??

By Rich Pope, Department of Plant Pathology

Cooler-than-normal weather continued as September dawned in Iowa. During the first week of September, Iowa lost about an additional 25 degree days to normal. This isn't great, but then not a crisis either. Open, sunny days and moderately warm temperatures are key to maturing and drying crops in the fields.

The Aug. 31, 2009 USDA crop condition report listed 76 percent of both corn and soybean acres in good to excellent condition. But the question now relates to dry down and potential harvest issues.  

Worries about a potential early killing frost are reasonable in most areas as well. There is no definitive predictor this far out that I know of for determining the likelihood of an early frost, and time will tell, of course.

Iowa map showing degree day departures for the season through Sept. 6.

As harvest approaches, keep in mind assessment of stalk strength to estimate standability of corn. That might help you schedule harvest to avoid losses. See this article by Alison Robertson that describes the process that was published last year in the ICM News.  


Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted at or by calling (515) 294-5899.

This article was published originally on 9/14/2009 The information contained within the article may or may not be up to date depending on when you are accessing the information.

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