Yield Loss in Wind Damaged Corn

August 30, 2011 in Uncategorized

Many corn fields in the county have experienced wind damaged corn resulting in severely lodged corn.  Delays this spring caused by wet weather lead to a large amount of late planted corn.  Yield losses in corn are experienced when the corn plant is damaged before physiological maturity (kernel black layer).  Below is an article on what to expect when corn is prematurely killed:

Severely damaged immature corn will likely shut down prematurely (kernel black layer development). If silage is an option, obviously that would be a preferred choice for utilizing immature corn that is severely flattened.

Dry down of grain (mature or immature) will be slower where ears are literally lying near the soil surface simply because they are less exposed to sun and wind. Less-severely lodged corn will dry at fairly normal rates.
It is important to understand what the current crop stage is at now and where it was at the time of the storm. Listed below is a description of the dent stages of field corn as it relates to corn maturity:
Kernel Dent Stage (R5). About 35 to 42 days after silking, all or nearly all of the kernels are denting near their crowns. A distinct horizontal line appears near the dent end of the kernel and slowly progresses to the tip end of the kernel over the next 3 weeks or so. This line is called the ‘milk line’ and marks the boundary between the liquid (milky) and solid (starchy) areas of the maturing kernels. Severe stress can continue to limit kernel dry weight accumulation. Kernel moisture content at the beginning of the dent stage is approximately 55 percent. Generally the amount of time it takes to go from dent to black layer is about 25 days (10 days from dent to 50% kernel milk stage, and 10 days from 50% kernel milk stage to black layer).
Physiological Maturity (R6) and Volunteer Corn potential. About 55 to 60 days after silking, kernel dry weight usually reaches its maximum and kernels are said to be physiologically mature and safe from frost. Physiological maturity occurs shortly after the kernel milk line disappears and just before the kernel black layer forms at the tip of the kernels. Severe stress after physiological maturity has little effect on grain yield, unless the integrity of the stalk or ear is compromised (e.g., ECB damage or stalk rots). Kernel moisture content at physiological maturity averages 30 percent, but can vary from 25 to 40 percent grain moisture. Thus ears with kernel moisture of 40% moisture or less will continue to progress to black layer even if the stalks were “crimped over” but not broken off completely. Therefore grain harvest is possible for these ears as well as the problem of viable kernels resulting in volunteer corn next growing season.

Premature Plant Death

Severe lodging resulting in stalk breakage prior to physiological maturity can cause premature leaf death or whole plant death. Premature death of leaves results in yield losses because the photosynthetic ‘factory’ output is greatly reduced. The plant may remobilize stored carbohydrates from the leaves or stalk tissue to the developing ears, but yield potential will still be lost.
Premature death of whole plants results in greater yield losses than if only leaves are killed. Death of all plant tissue prevents any further remobilization of stored carbohydrates to the developing ear. Whole plant death that occurs before normal black layer formation will cause premature black layer development, resulting in incomplete grain fill and lightweight, chaffy grain. Grain moisture will be greater than 35%, requiring substantial field drydown before harvest.

Effect on Grain Quality

Growers should recognize that possible development of ear molds resulting from direct or rain-splash contact with fungi and bacteria on ears lying near or at the soil surface obviously increases the risk of poor grain quality. That risk plus potential kernel sprouting in ears lying close to the soil surface could increase grain quality headaches for growers on the worst lodged fields or areas of fields.
Growers may need to consider the segregation of grain storage from severely lodged areas from the rest of their corn if possible to avoid grain quality discounts when marketing the grain later. The U.S. marketing standards for corn allow up to 5% total damaged corn kernels in U.S. No. 2 corn.
The best guide for correct combine adjustments is your operator’s manual. Remember that gathering head losses usually represent the greatest source of loss for the combine.
  • Use a ground speed of 2.8 to 3.0 miles per hour.
  • Close the stripper plates or snapping bars only enough to prevent ears from passing through.
  • The chain flights over the stripper plates should extend beyond the edge of the plates about 1/4 inch.
  • Ears should be snapped near the upper third of the snapping roll.
  • Gathering snouts should float on the ground, and gathering chains should be just above the ground.
  • Measure losses and make corrective machine adjustments whenever crop conditions change.
Use plastic snouts and reels to help pick up lodged corn and move it off the corn head and into the combine. Below is a list of manufactures and dealers for combine snouts and reels.
The Kelderman reel moves the corn off the header and into the combine to allow the combine to continuously move forward.
Kelderman Equipment
2686 Highway 92 East
Oskaloosa, IA 52577-9685
Phone: 800-334-6150
The Meteer corn reel is very similar to the Kelderman reel. Its revolving fingers help to feed lodged corn into the head, saving down corn that would otherwise be lost.
Meteer Manufacturing
RR1 Box 221
Athens, IL 62613
Phone: 217-636-8109
The Roll-A-Cone Manufacturing Company has two different types of plastic cone attachments, one for a corn head and the other for a soybean-type head.
Roll-A-Cone Mfg. Co.
Rt. 2, Box 25
Tulia, Texas 79088
Phone: 806-668-4722
If plants are extremely lodged and stalks and roots are badly deteriorated, a high number of ears may be lost over the outside snouts of a regular corn head. This is especially true if roots are easily pulled from the soil during harvest. In such cases another harvest option is to use a soybean platform head to completely cut the plants off. This may reduce the instances of corn trash plugging the head as well.
Disengage power and shut off engine before making any adjustments. Stalk rolls turn faster than you can react to release plugged stalks. Keep shields in place. Mechanically lock and block the corn head before getting underneath it. Carry two fire extinguishers, a small one inside the can and a 10-pound unit at ground level.
From Nicolai, Dave & Dale Hicks.  2006. Corn Development and Maturity as Affected by Wind Storm Damage.  University of Minnesota Extension.  Minnesota Crop News.  http://www.extension.umn.edu/cropenews/2006/06MNCN53.htm

Corn Harveting Equipment for Wind Damaged Corn

August 29, 2011 in Uncategorized

Hurricane Irene has caused significant lodging in corn fields.  Drought and high temperatures during and after pollination left corn fields with weakened stalks.  Stalk rots in dryland corn are also common this year.  Recovering lodged corn can be a challenge.  Below are companies that make attachments for corn heads that help to recover wind damaged corn:

Heritage Machine & Welding
1001 W. Locust
Bloomington, IL 61701
(800) 274-0440
Corn Reel by Minden Machine Shop Inc.
1302 K Road
Minden, NE 68959
(800) 264-6587
Corn Saver
5200 N. Columbia St.
Plainview, TX 79072
(800) 536-1022
The Kelderman Reel
Kelderman Manufacturing, Inc.
2686 Highway 92 East
Oskaloosa, IA 52577
(800) 334-6150
The Meteer Corn Reel
Meteer Manufacturing
RR1 Box 221
Athens, IL 62613
(217) 636-8109
The Roll-A-Cone
Roll-A-Cone Manufacturing
7655 Roll-A-Cone Road
Tulia, TX 79088
(806) 668-4722
St. John Welding and Manufacturing, Inc.
P.O. Box 175
St. John, KS 67576
(800) 549-3289
Storm Reel
Lofquist Welding Inc.
P.O. Box 365
202 Ontario Avenue
Elwood, NE 68937
From Roth, Greg. 2011.  Corn Harvesting Equipment for Wind Damaged Corn.  Penn State Corn and Soybean Management website.  http://cornandsoybeans.psu.edu/lodgeequipment.cfm

Stalk Rots In Corn

August 24, 2011 in Uncategorized

Some corn fields in the county are showing symptoms of stalk rot.  This can make an earlier harvest more desirable as a storm with strong winds and rain can cause severe lodging.  Below is an article from Arv Grybauskas, Extension Plant Pathologist, University of Maryland describing why stalk rots occur and why scouting should occur now.  The article is from last year, but pertains to conditions that parts of the county are experiencing.

Corn harvest will begin earlier this season due to the high average temperatures increasing the speed with which growing degree-days (GDD) have accumulated. Typically in seasons characterized by high temperatures and droughty conditions there is an increase in stalk rots and certain ear rots. Most notably two fungal ear rots that can produce toxins in the grain, Aspergillus and Fusarium ear rot, are favored by these conditions. The more dangerous of the two is Aspergillus. Aspergillus infected kernels can contain the carcinogenic toxins known as aflatoxins.
Aspergillus is a fungus that is highly tolerant of high temperatures. Because of its high temperature tolerance it is the most prevalent ear-infecting fungus during hot dry conditions. The fungus survives is soil and crop debris and is spread to silks by wind and insects. The use of certain types of BT corn have helped reduce the incidence of Aspergillus infection by reducing the insect-associated infections but direct infections are still possible. Stressed corn appears to be more susceptible to infection. Typically only a few kernels near the tip are infected by Aspergillus, but tolerance levels for aflatoxin are in parts per billion (e.g. 20 ppb for human consumption). A blacklight is commonly employed as a quick preliminary test for aflatoxin contamination. A sample of cracked or coarsely ground kernels is illuminated with a blacklight and viewed for a yellow-green fluorescence. It is important to know that the fluorescing material is not aflatoxin itself but often is an indicator of (correlated with) aflatoxin. Other material will fluoresce under blacklight like corn glumes (a.k.a. beeswings), certain weed seeds, and uninfected kernel tips, so that false positives are possible. Since the advisory limits are at ppb levels false negatives are also possible with the blacklight test. There are commercially available rapid test kits that provide better and in many cases quantitative detection, as well as commercial labs that will test for toxins.
Similarly, Fusarium ear and kernel rot is favored by high temperatures and droughty conditions especially when they occur near flowering. There are several species of Fusarium that are involved but generally are different from the primary species that cause scab in wheat. Fusarium ear and kernel rot is important because of a production of a class of toxins known as Fumonisins. Fumonisins are known to cause equine leukoencephalomalacia, “blind staggers” in horses and pulmonary edema in swine, and have been linked to human cancers in other parts of the world. Different tests are required to detect Fumonisins.
Stalk rots caused by fungi leading to premature lodging are also generally favored by stressful growing seasons. In general any stress on the corn plant can lead to insufficient capacity of the plant to provide photosynthate to the developing ear. When the capacity is exceeded the plant mobilizes stored carbohydrates from the stalks to fill the demand. This leads to premature senescence of stalk tissue and predisposes the plant to colonization by any number of opportunistic stalk rotting fungi.
Regardless of the stalk rot or ear rot, there are a few things that can be done to minimize losses and improve the harvestablity. First, harvest the corn at high grain moisture (25 to 27%), and make sure the combine is adjusted properly to minimize cracking. Harvesting as early as practical reduces the time that the damaging fungi have at colonizing the tissue. This reduces lodging due to stalk rots, kernel infection and toxin development. Cracked kernels are more susceptible to post-harvest colonization and toxin development. You can also use simple pre-harvest stalk testing to determine which fields are at greater risk for lodging to schedule harvest accordingly. You can pinch stalk internodes to determine a percentage that are soft and likely to lodge if left in the field, or you can use the push test. The push test is simply pushing corn stalks at arms length and determining the percentage that break. In both cases the greater the number of plants and sites scouted the better the information. A rule of thumb I like is 10 stalks in 10 sites for every 10 acres. It is also important to note that fungicides used near tassel will not have a direct effect on stalk rotting. If there was a foliar disease then fungicides reduce the stress associated with the foliar disease and this indirectly reduces stalk rotting. There is no fungicide residue available by the time stalks are predisposed to stalk rotting fungi to directly affect the colonization by these fungal organisms.
Secondly, to reduce the damage from ear rots and in particular to keep toxin development to a minimum, after harvesting corn at high moisture with careful attention to reduce cracking, dry the corn as soon as possible (within a day or two) to 15.5% moisture or lower. The ear rotting fungi continue to grow in high moisture corn in the bin. Controlling moisture and temperature of harvested corn is the most cost-effective method of preventing spoilage.

Information from “Plan Ahead to Deal with Corn Stalk Rots, Ear Rots and Toxins in Grain”.  Arvydas (Arv) Grybauskas, Extension Plant Pathologist, University of Maryland.  August 10, 2010 Weekly Crop Update.

Corn – Stalk Strength Poor This Year in Many Fields

September 29, 2009 in Uncategorized

I have looked at many corn fields and stalk strength is often poor this year. The following are some causes.

  • The primary reason for poor stalk strength this year is corn diseases, both stalk rots and foliar diseases. Fungal stalk rots weaken stalk strength directly (essentially digesting the stalk). Leaf diseases reduced carbohydrate production and therefore storage reserves in the stalk thus weakening stalks.
  • Root rots are also common this year, weakening plants and causing small diameter stalks and poor stalk quality as well as root lodging.
  • Nitrogen deficiencies are evident in many fields this year with the heavy leaching with excess rainfall and some field areas not receiving enough N due to wet conditions. Nitrogen deficient plants have smaller stalk diameters and are more prone to lodging.
  • Water damage and late planting have caused weaker plants more prone to lodging.

The following is from Bob Mulrooney, Extension Plant Pathologist, UD:

The common late-season stalk rots are caused by fungi and include: Gibberella stalk rot (Gibberella zeae = Fusarium graminearum), anthracnose (Colletotrichum graminicola), Fusarium stalk rot (Fusarium moniliforme), charcoal rot (Macrophomina phaseolina), and Diplodia stalk rot (Diplodia maydis). It is common for more than one stalk rot organism to attack a plant at the same time.

Be sure to check corn fields for lodging potential by squeezing the lower nodes or pushing on the stalks. A simple way to do this is to walk through the field and, keeping your hands at chest height, push stalks 8-10 inches from vertical. If 10-15% of the stalks lodge, schedule the field for early harvest before a strong wind results in severe lodging.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Red Root Rot in Corn

October 4, 2008 in Uncategorized

I recently looked at a corn field where large spots were heavily lodged and had reduced yields. Upon examination, the roots of the corn were found to be infected and had a dark red coloration. We are currently culturing the roots to determine the exact cause but the initial diagnosis is Red Root Rot. The following are exerpts from an article on Red Root Rot by Dr. Bob Carroll, a plant pathologist that worked at the University of Delaware for many years until recent retirement.

Red root rot has increased in incidence and severity since the late 1980s. The disease has been most prevalent in the Atlantic states, especially the Delmarva region (Delaware, Maryland, and the Virginia peninsula), where yield reductions of 15-20% have occurred in localized areas. It is now being found in many other states with reports from Colorado, Missouri, North Carolina, and Oregon.


Red root rot is usually not apparent until just prior to senescence (corn maturity). The major symptom, as implied by the name, is the reddish pink discoloration of the root system and basal stalk tissue. There is a reduction in total root mass, which is obvious when a comparison is made with roots of a nearby healthy plant. As the rot continues, the color of the roots often progresses from reddish pink to deep carmine and is accompanied by necrosis and shriveling of the root tissue. A similarly colored rot can be observed in basal stalk tissue and generally does not extend more than three elongated internodes above the soil line. The red color may be confused with that associated with Gibberella stalk and root rot. However, the discoloration associated with red root rot is usually darker. Aboveground, the most obvious symptom of the disease occurs during the late stages of ear fill and is characterized by premature death of the plant. As with many stalk rot diseases, foliage and stalks become grayish green, and leaves have an overall wilted appearance. Foliar symptoms occur quickly, usually in a 4- to 5-day interval, and death of the most susceptible plants occurs within a week. This may be followed by severe lodging, depending on weather condidons. Symptoms have been observed most frequently in the Delmarva region when corn is grown in a “high-yield” (high-population, high-fertility, irrigated) environment. The rate of disease development varies greatly among varieties.

Causal Organism

Several studies have indicated that red root rot is caused by a complex of fungi that includes Phoma terrestris as the primary pathogen in association with Pythium and Fusarium species.

Disease Cycle and Epidemiology

P. terrestris is recognized as a widespread saprophyte and weak parasite on the underground parts of a wide variety of hosts. The most studied and economically destructive disease caused by this pathogen is pink root of onion, and much remains to be learned about the disease on com. The fungus occurs in many types of soils and survives well under a wide range of temperature and pH conditions. The fungus can survive in the soil for years, presumably as microsclerotia, which may serve as the overwintering structures and the primary inoculum. There is a general lack of information about the importance of the pycnidial stage, and a sexual stage has not been found. In some research, P. terrestris was detected in corn roots as early as the midsilking stage but not consistently. It is generally considered a late-season pathogen that can be successfully recovered from infected corn roots beginning in early August or later. The rate of colonization of root and basal stalk tissue increases as the host undergoes senescence. Deterioration of infected roots results in loss of vigor, accelerated senescence, wilting of leaves, stalk lodging, and reduced yield. In both corn and onion, P terrestris propagules invade root epidermal and cortical dssue. Hyphal advance and penetration of host cells are facilitated primarily by enzyme breakdown of host cell wall tissue. Recent research indicates that early infection of corn roots by Pythium spp. (and perhaps other fungi) debilitates the roots to the extent that P. terrestris is able to invade earlier and/or more effectively as an important secondary pathogen, resuldng in red root rot.


It is extremely difficult to evaluate breeding materials for suscepdbility or resistance to P. terrestris. As with many other root-infecting fungi, it is likely that through extensive testing of corn hybrids over wide geographical areas, those that have some resistance are selected. Studies on inheritance of resistance indicate that resistance is a polygenic trait with additive gene action. Crop rotation with soybeans seems to provide some control.

Red root rot, note the deep red color of some roots.

Red root rot infected corn roots. This corn plant pulled up easily and the root system was severely affected.

Corn lodging in an area of a field infected by red root rot.

Information from “Red Root Rot of Corn” Prepared by R.B. Carroll – Compendium of Corn Diseases – Third Edition, APS Press – The American Phytopathological Society. Photos by Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Corn Lodging

September 11, 2008 in Uncategorized

There are reports of severe corn lodging across the county making harvest more difficult. Stalk strength is very poor with the August drought. Hanna caused significant lodging but it was less than expected. Recent thunderstorms had some severe local effects causing downed corn where there were heavy wind gusts with the rain. The following are some pictures I took recently of lodged corn after Tuesday’s thunderstorms. Most corn is able to be picked up with the head and there is not a lot of ear drop so far. Additional storms will cause more harvest problems.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Drought and Stalk Strength in Corn

August 27, 2008 in Uncategorized

Exceptionally dry weather has plagued many corn fields since late July. Drought conditions experienced during grain fill often increase the potential for lodging problems in corn. The following is more information.

Corn plants must produce enough carbohydrates by photosynthesis to keep root cells and pith cells in the stalk alive and enough to meet demands for grain fill. When corn is subjected to severe drought stress, photosynthetic activity is sharply reduced as leaves roll tightly and plant growth slows. As a result, the carbohydrate levels available for the developing ear are insufficient. The corn plant responds to this situation by removing carbohydrates from the leaves, stalk, and roots to the developing ear. While this “cannibalization” process ensures a supply of carbohydrates for the developing ear, the removal of carbohydrates results in premature death of pith cells in the stalk and root tissues. This weakens the stalk. It also predisposes plants to root and stalk infection by fungi and increases stalk rots.

As plants near maturity, this removal of nutrients from the stalk to the developing grain results in a rapid deterioration of the lower portion of corn plants in drought stressed fields with lower leaves appearing to be nitrogen stressed, brown, and/or dead. Other plant stresses which increase the likelihood of stalk problems include: loss of leaf tissue due to foliar diseases (such as gray leaf spot or northern corn leaf blight), insects, or hail; injury to the root system by insects or chemicals; high levels of nitrogen in relation to potassium; compacted soils restricting root growth; and high plant populations. Most hybrids do not begin to show stalk problems until shortly before physiological maturity.

Adapted from “Dry Weather May Lead to Stalk Lodging Problems in Corn” by Peter Thomison, Pierce Paul, Dennis Mills in the August 25 CORN newsletter from the Ohio State University.