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Ohio State University Extension


C.O.R.N. Newsletter 2007-28

Dates Covered: 
August 27, 2007 - September 4, 2007
Todd Mangen

Late Season Flood Damage to Corn: Management Considerations

Authors: Peter Thomison, Pierce Paul, Dennis Mills

Recent flooding in parts of Ohio, especially the NW counties, has caused major damage to many cornfields. In some river bottoms, corn was immersed up to the tassels. Since much of the corn was shorter than normal (with low ear height - due to drought conditions), the likelihood that ears were immersed by flood waters was greater. Much of the corn was in the dent stage when flooded. The impact of this flood damage on corn will be highly dependent on kernel stage of development, length of the flooding period, how much of the corn plant was immersed during flooding, and subsequent weather conditions.

Since late season flooding is an uncommon event, little information is available on its effects on corn at this stage of kernel development, and how to best salvage damaged corn. A major concern is the impact of flooding on grain and silage quality. In past reports, when corn in the dent stage was covered by flood water for six hours or more and nearly completely caked with mud for up to two weeks, damage from ear rots and premature kernel sprouting was extensive in those areas of fields where water had covered the ears the longest. Although such damage may be negligible in fields where water never covered the ears, prolonged flooding may cause significant injury to the roots, if not premature root death. Such plants will be more vulnerable to stalk rots thereby increasing the likelihood of stalk lodging, especially if harvesting is delayed. Therefore, as soon as plants have dried, stalks should be inspected to determine the degree of rot. If rot is extensive, these affected fields should be harvested first to minimize further yield loss.

Another issue that may impact injury from immersion is whether ears were in an upright or downward position when flooded. If most plants had not yet reached black layer when flooding occurred, most ears were probably in an upright position which would probably result in ears catching and retaining more soil, etc. Corn growers in the South have observed that once the ears are soaked from flooding, they quickly rot at high temperatures so prompt harvesting is necessary. Moreover, soaked ears are often associated with premature kernel sprouting, which can lead to secondary bird damage and insect feeding, especially if husks are loose.

The combined effects of excess moisture, bird and insect damage and warm temperatures may also result in ears being colonized by mycotoxin producing molds. In general, mold development and ear rots are of greater concern when favorable weather occurs during silk development, however, fungi may also infect and cause ear rot late in the season, especially if ears remain in an upright position and accumulate soil and moisture. Normally, healthy, intact kernels at the dent growth stage are not easily infected by fungi, however, these same kernels softened by excess moisture and damaged by birds become easy targets for both saprophytic fungi (and bacteria) and ear rots, most of which are present in soil particles and debris found in flood waters. Samples of grain harvested from flooded fields, especially if ears were covered with flood water for extended periods or plants were lodged, should be sent for toxin analysis before feeding grain to animals. Laboratories for mycotoxin analysis can be found on the Ohio Field Crop Disease web site
When dealing with flood damaged corn, a common suggestion is to allow rains to wash off as much soil as possible before harvesting. Another observation is that flooding often deposits considerable debris on fields making harvesting difficult, as will dust associated with soiled plants.

For more information on salvaging corn damaged by late season floods, consult the Penn State Corn and Soybean Management website - Managing Flood Damaged Crops

Feeding Flood-Damaged Corn

Authors: Bill Weiss

The two primary concerns regarding feeding flood-damaged corn to cattle are soil contamination and microbial contamination.

1. Soil contamination will be much worse for silage than for grain since most of the soil is trapped on lower parts of the plant. Silage made from corn that has been flooded should be analyzed for total ash and minerals. Normal corn silage has about 4 to 4.5% ash (dry matter basis) but flood-damaged silage could have 5 to 7% ash. Soil contamination will reduce the energy value of silage (ash has no energy) and can reduce availability of certain essential minerals, especially copper. If the silage has high ash concentrations make sure the estimated energy value of the silage was calculated from equations that consider ash. If the estimated value does not consider ash, on average high ash corn silage (approximately 6%) will have about 3 to 4% less energy than normal corn silage. Dietary copper should also be increased when high-ash silage makes up a substantial portion of the diet. In most situations, diets that provide about 20 ppm of total copper should be adequate. Soil contamination is not a major concern when flood-damaged corn grain is fed.

2. Microbial contamination caused by flooding can increase the risk of a poor fermentation (silage) and increase the risk of mold and mycotoxin development in both silage and grain. Although no data are available supporting this recommendation, using a proven corn silage inoculant (per manufacturers directions) may reduce the risk of poor fermentation caused by flooding. Good silage making practices (filling rapidly, good packing, covering the silage, letting it sit undisturbed for several weeks after filling) are always important but are even more important when the risk of a poor fermentation is high. The risk of mold and mycotoxin contamination is higher for flood damaged corn grain and silage (remember you can have moldy feed without mycotoxins). For silage, the best remedy is to promote a good fermentation which should inhibit mold growth. Good grain storage procedures will help reduce continued mold growth in grain. Although labs can run assays for some mycotoxins and some labs can provide information on mold counts, collecting a good sample of grain and especially silage is problematic. False negatives are likely because mold and mycotoxins are not spread uniformly within the silage mass. If mycotoxin problems are suspected based on animal performance, talk with your nutritionists about feed additives and other management practices that might help reduce the problem.

Flooding Injury to Soybeans

Authors: Anne Dorrance, Jim Beuerlein

Too much rain hit parts of Ohio last week with the remnants of tropical storm Erin. In some fields, the plants were totally covered, so these will be lost. For other fields, the combination of the fields being very dry (so they could absorb the moisture) combined with our excellent drainage systems, the water moved away quite quickly. From previous studies at The Ohio State University, by Dr. Tara VanToai’s group has demonstrated that it takes 3-days of saturated conditions before much root injury takes place. After the 3-days, the carbon dioxide builds up in the soil creating anaerobic conditions (no oxygen) and then root injury occurs. When you walk into the fields you will be able to smell when this occurred. It smells like a swamp. The amount of injury to the crop and impact on yield is going to be dependent on several factors: the length of time the field was flooded, the health of the crop before flooding; and the growth stage. If the plants were in earlier reproductive phases they will be impacted the most while other later growth stages will most likely show little damage.

Soybean Rust Update

Authors: Anne Dorrance

From the Soybean Rust website (, this is where the model forecasters have been placing weather data. Last week they were predicting that soybean rust spores (August 19-22) were picked up on tropical storm Erin and potentially deposited in Ohio. Don’t panic, don’t get excited and don’t get out the fungicide sprayers. These are predictions/speculations and as part of this, the inoculum levels are very, very low¬ (10 spores per 2.5 acres). To put this in a better perspective, when researchers inoculate in the greenhouse they need 1,000 spores/ml and 2 to 3 mls (1ml = 5 teaspoons) are applied to each plant in order to get 1 to 2 pustules per leaf. If the modelers were correct and soybean rust spores were deposited in Ohio last week, and those spores were viable and they landed on a soybean leaf and did not end up in the river, it would take us until mid-week this week (August 29) to find the first pustule and more likely 3 weeks to find the leaves/area where an infection occurred (due to the very low levels of inoculum) this would still be at very low incidence/severity for a field and well within anytime frame to make recommendations for our double crop. Our normal sampling will continue this week, but we will begin to increase our sampling – more fields and more locations following Labor day to determine: a.) if rust is present b.) if these model predictions were correct. Basically now the ground-truthing can begin. In a case like this with spores from a hurricane or tropical storm, the inoculum is so diluted over the region that we can monitor the sentinel plots to make individual county/region fungicide predictions. Most of Ohio’s crop is well past any effect of this fungus on the crop.

This is a good time to remind everyone that our sentinel plot system has 2 purposes: 1.) information for our own fungicide recommendations 2.) ground-truthing for these models. It will be interesting if this prediction proves to be true...we are not recommending any fungicides at this time and we still are required to go through the process of having USDA confirm a positive find. You are more than welcome to submit samples to our labs if in your scouting you find anything suspicious.

Ryegrass Cover Crop Risks in Kentucky Fields

Authors - James R. Martin, William W. Witt, and J.D. Green, Plant and Soil Sciences (This article originally appeared in the August 2007 edition of the Corn and Soybean News, University of Kentucky)

Seeding annual ryegrass as a cover crop has been promoted in a number of areas in annual and perennial cropping systems. While there may be benefits with this practice, grain crop growers need to be aware of the potential drawbacks encountered when seeding ryegrass as a cover crop in Kentucky.

Corn Problems:
Ryegrass can compete with young corn plants during early spring and often harbor rodents that eventually feed on corn seed. Therefore, killing ryegrass vegetation well in advance of planting no-till corn is necessary to avoid these problems. Controlling ryegrass in no-till corn requires good management skills and additional expense. A high rate of glyphosate may provide acceptable control, but it requires several weeks for ryegrass to die. This slow activity of glyphosate during early spring may not be acceptable for managing a heavy infestation of ryegrass prior to planting no-till corn.

University of Kentucky research shows that sequential applications offer the best method for managing ryegrass in no-till corn. One approach is to apply paraquat or glyphosate as two burndown applications with an interval of 7 to 10 days between treatments. If rapid kill of top growth of ryegrass is needed, paraquat should be included in at least one of the burndown treatments. Another approach is to apply a single burndown spray of either paraquat or glyphosate at planting followed by a postemergence spray of Accent, Option, Steadfast, Lightning (in Clearfield Corn) or glyphosate (in Roundup Ready corn), 3 to 5 weeks after planting. It is important to recognize that sequential programs will not provide 100% control of annual ryegrass consistently. Furthermore, sequential programs require extra time and additional expense that can range from $ 10.75 to $ 31.50/A.

Transitioning to Other Crops:
The risk of ryegrass emerging as a ‘weedy’ plant in subsequent crops is another factor to consider when using ryegrass as a vegetative cover in a grain crop rotation. This problem is very likely to occur where ryegrass plants initially escape control in corn and are able to produce viable seeds that germinate the following fall. Carryover of seeds in the soil can also contribute to future problems with ryegrass. While most ryegrass seeds germinate soon after exposure to a favorable environment, research has shown that a small percentage of seeds can remain viable in soil six to seven years. Therefore, even if a ryegrass cover crop is completely killed, there is a chance that seeds remaining in soil can develop as a problem in subsequent crops such as wheat.

Wheat Problems:
Ryegrass is especially competitive in wheat because it can emerge quickly in the fall and grow rapidly in early spring. One ryegrass plant per square foot can reduce wheat yield by approximately 4 percent. Management skills are as important in wheat as they are in corn. Sporadic emergence patterns of ryegrass challenges the grower in determining the optimum time to spray for this weed. Preventing ryegrass plants from producing seed is particularly important since its seeds are easily spread during the harvesting process. A few ryegrass plants that escape control in wheat can evolve into a major infestation in subsequent crops in a short period of time. A large drawback in dealing with ryegrass in wheat is the cost of using herbicides which can range from $16.75 to $29.50/A.

Potential “Fit” for Ryegrass
Good seedling vigor, fast emergence, and low cost make ryegrass attractive for certain areas prone to erosion. A seed mixture of ryegrass with tall fescue may help establish a sod cover for waterways or highly eroded slopes that are not used for grain crop production. Nevertheless, these areas need to be properly managed to limit spreading ryegrass seed to fields used for producing grain crops. This includes clipping or mowing these areas before ryegrass plants mature to limit new seed production, especially areas in close proximity to fields used for grain production. Keeping mowing equipment clean of seed will also help contain ryegrass.

Lacefield, G., M. Collins, J. Henning. Tim Phillips, M. Rasnake, R. Spitaleri, D. Grigson, and K. Turner. Annual Ryegrass. AGR-179. 2005.

Liebl, R. and A.D. Worsham. Interference of Italian Ryegrass (Lolium multiflorum) in wheat (Triticum aestivum). Weed Science, 1987. Vol. 35: 819-823.

Martin, J. R. Ryegrass – Crop or Weed. Kentuckiana Proceedings, Dec 1993.

Martin, J. R., W. W. Witt, and D. L. Call. Feb. 1999. Managing Italian Ryegrass in Wheat and No-tillage Corn. Proc. of the 4th National Wheat Industry Research Forum. pp. 31-33.

Martin, J. R. and C. H. Slack. 2005. Factors Affecting Burndown Control of Italian Ryegrass with Glyphosate. 2005. Proc. of Southern Conservation Tillage Systems Conference. 27: 166.

Martin, J. R., D. Call, and J. James. 2003. Italian Ryegrass Control with Wheat Herbicides. Proc. of Southern Weed Science Society. 56: 307.

Martin, J. R., J. D. Green, and W. W. Witt, 2001. Italian Ryegrass (Lolium multiflorum) Control in No-Tillage Corn. Proc. of Weed Science Society of America 41: 1-2.

Nickel, K. l. Going Deep with Annual Ryegrass. CTIC Partners. Oct, 2006. Vol. 24, No 3.

Rampton, H. H. and T. M Ching. Persistence of Crop Seed in Soil. Agronomy Journal, Mar-Apr 1970, Vol. 62: 272-277.

Flooded Soil and Bad Odors, Can Anything Be Done?

Authors: Robert Mullen

Recent floods have saturated many soils and as a result some rather offensive odors may be emanating from these soils. The question is being asked – what can be done?

First, let’s discuss the source of the odor. As a soil becomes saturated with water, oxygen becomes limiting and that is a problem for obligate aerobes (organisms that require atmospheric oxygen). The absence of atmospheric oxygen will allow organisms that are adapted to oxygen limiting/anaerobic conditions (obligate anaerobes and facultative anaerobes) to flourish if an abundant carbon source is available. Like most other organisms the anaerobes require carbon, but instead of generating carbon dioxide as an end product of metabolism methane is produced. This is mostly likely the source of the foul odor coming from your soil.

Now that we know what is causing the odor – what can we do about it? Unfortunately very little. The best course of action is to allow the soil to dry. As oxygen returns to the soil system the aerobic organisms will once again return and it will be back to business as usual.

GVM West and OSU Extension Field Day; September 6th

Authors: Steve Prochaska, Mike Gastier

8:00 – 9:00 am Free Registration – Coffee- Donuts
9:15 – 9:45 am Raven Presentation: AutoBoom, AccuBoom, Viper, Light Bars
- Register to Win a RGL600 Lightbars
9:50 – 10:20 am TeeJet Presentation: Filed Pilot, Light Bar, Spray Nozzles
- Register to Winn a Centerline 220 Lightbar
10:30 – 12:00 Noon GVM Ride & Drive , Visit Vendors
10:30 – 11:15 am OSU – Variant Western Corn Rootworm & Soybean Aphid Update
Category 1 Pesticide ½ hour CCA & Restricted Use Credits
Presented By: Ron Hammond, OSU Extension
11:15 – 11:45 am OSU Fungicide Use on Corn and Soybeans: What & When
Category 1 Pesticide ½ hour CCA & Restricted Use Credits
Presented By: Dennis Mills, OSU Extension
11:45 – 12:15 pm OSU Pesticide Law Regulations Update/IPM Concepts
½ hour CORE Credit (Attend both sessions for 1 hour credit)
Presented By: Steve Prochaska, OSU Extension
12:00 – 1:00 pm Lunch
1:00 – 2:00 pm OSU Weed Control Update & Weed ID and Diagnostic Session
Category 1 Pesticide ½ hour CCA & Restricted Use Credits
Presented By: Jeff Stachler, OSU Extension
1:15 pm Pan Test of GVM Fusion Dual Product Spreader – VRT (in the Field), GVM Ride & Drive Continues, Visit Vendors
2:00 – 2:30 pm OSU Ohio Pesticide Law Regulation Update/IPM Concepts
½ hour CORE Credit (Attend both sessions for 1 hour credit)
Presented By: Mike Gastier, OSU Extension

CCA Credits: 2 ½ hours Pest Management; ½ hour Crop Management.
Pesticide Applicator Commercial Credits:1 hour Core, 1 hour Category 1 & ½ hour category 2a and 2c.
RSVP at 1-800-848-8460, GVM West – 4341 Sandhill Road, Bellevue, OH 44811
Field will be located on Sandhill Raod just South of Route 20 and 1 ½ miles east of Route 4 and Route 20 interchange.

Archive Issue Contributors: 

State Specialists: Anne Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond (Entomology), Mark Loux and Jeff Stachler (Weed Science), Peter Thomison (Corn Production), Bill Weiss (Animal Science), Jim Beuerlein (Small Grain Production) Robert Mullen (Soil Fertility). Extension Educators: Roger Bender (Shelby), Todd Mangen (Mercer), Jonah Johnson (Clark), Gary Wilson (Hancock), Glen Arnold (Putnam), Mike Gastier (Huron), Greg Labarge (Fulton), Ed Lentz (Seneca), Mark Koenig (Sandusky/Ottawa), Steve Prochaska (Crawford), Wesley Haun (Logan), Bruce Clevenger (Defiance).

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.