C.O.R.N. Newsletter 2008-28

Dates Covered: 
August 25, 2008 - September 2, 2008
Editor: 
Andy Kleinschmidt

Dry Weather May Lead to Stalk Lodging Problems in Corn

Authors: Peter Thomison, Pierce Paul, Dennis Mills

Exceptionally dry weather has plagued many corn fields since early July. Drought conditions experienced during grain fill often increase the potential for stalk rot and lodging problems in corn. When stalk rot occurs late in the season as it often does, it may have little or no direct effect on yield. Nevertheless, stalk lodging, which results from stalk rot, can have such an impact on harvest losses that many plant pathologists consider stalk rots to be the most significant yield limiting disease of corn.

For a corn plant to remain healthy and free of stalk rot, the plant 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, which predisposes plants to root and stalk infection by fungi. Even mild, early season water stress during the pretassel stage of development can significantly increase root infection by stalk rot fungi and result in greater stalk rot at maturity. 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 rot 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 or saturated soils restricting root growth (recent flooding); and high plant populations.

Most hybrids do not begin to show stalk rot symptoms until shortly before physiological maturity. It is difficult to distinguish between stalk rots caused by different fungi because two or more fungi may be involved. Similarly, certain insects such as European corn borer often act in concert with fungal pathogens to cause stalk rot. Although a number of different fungal pathogens cause stalk rots, the three most important in Ohio are Gibberella, Collectotrichum (anthracnose), and Fusarium. For more information on stalk rot in corn, consult the OSU Plant Pathology web site "Ohio Field Crop Diseases" (http://www.oardc.ohio-state.edu/ohiofieldcropdisease/) for more details and pictures of the disease symptoms associated with these pathogens.

The presence of stalk rots in corn may not always result in stalk lodging, especially if the affected crop is harvest promptly. It’s not uncommon to walk corn fields where nearly every plant is upright yet nearly every plant is also showing stalk rot symptoms! Many hybrids have excellent rind strength, which contributes to plant standability even when the internal plant tissue has rotted or started to rot. However, strong rinds are not will not prevent lodging if harvest is delayed and the crop is subjected to weathering, e.g. strong winds and heavy rains.

A symptom common to all stalk rots is the deterioration of the inner stalk tissues so that one or more of the inner nodes can easily be compressed when squeezing the stalk between thumb and finger. It is possible by using this "squeeze test" to assess potential lodging if harvesting is not done promptly. The "push" test is another way to predict lodging. Push the stalks at the ear level, 6 to 8 inches from the vertical. If the stalk breaks between the ear and the lowest node, stalk rot is usually present. To minimize stalk rot damage, harvest promptly after physiological maturity (about 30% grain moisture). Harvest delays will increase the risk of stalk lodging and grain yield losses, and slow the harvest operation.

In addition to potential stalk rot problems, mycotoxins, especially aflatoxins, are major concerns in drought-stressed corn. Under normal conditions, aflatoxin contamination is not usually a problem in Ohio, but the dry conditions experienced across the state may lead to such problems this year. Drought-stressed corn is more susceptible to infection by Aspergillus flavus, an ear mold fungus that produces aflatoxins. As the corn dries down and we get closer to harvest, producers should start checking for ear molds by stripping back the husks and examining the ears of 80-100 plants sampled from across the entire field. Ear molds tend to be higher in insect damaged fields and are much easier to identify in the field than in harvested grain.

Since not all ear molds are associated with mycotoxin contamination, it is important to properly identify ear molds before harvest in order to determine if mycotoxin will be a concern and to make adequate marketing and storage decisions. For more on ear molds and mycotoxins, including sampling and testing for toxins, visit the field crops disease website at
http://www.oardc.ohio-state.edu/ohiofieldcropdisease/Mycotoxins/mycopagedefault.htm
http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/mycotoxin%20text2.htm

Potential for Nitrate Problems in Stressed Corn

Authors: Peter Thomison

Very dry to extremely dry soil conditions across Ohio have raised questions concerning the potential for toxic levels of nitrates in corn harvested for silage. Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in growing green leaves. Under unfavorable growing conditions, especially drought, this conversion process is retarded, causing nitrate to accumulate in the stalks, stems and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates and within a few days nitrate levels in the plant returns too normal.

The highest levels of nitrate accumulate when drought occurs during a period of heavy nitrate uptake by the corn plant. A drought during or immediately after pollination is often associated with the highest accumulation of nitrates. Extended drought prior to pollination is not necessarily a prelude to high accumulations of nitrate. The resumption of normal plant growth from a heavy rainfall will reduce nitrate accumulation in corn plants, and harvest should be delayed for at least 1 to 2 weeks after the rainfall. Not all drought conditions cause high nitrate levels in plant. If the supply of soil nitrates is in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates.

If growers want to salvage part of their drought damaged corn crop as silage, it's best to delay harvesting to maximize grain filling, if ears have formed. Even though leaves may be dying, the stalk and ear often have enough extra water for good keep. Kernels will continue to fill and the increases in dry matter will more than compensate for leaf loss unless plants are actually dying or dead. Moreover if nitrate levels are high or questionable, they will decrease as plant gets older and nitrates are converted to proteins in the ear.

For information on testing and feeding corn with varying nitrate-nitrogen levels, check out the following publication: Nitrates in Dairy Rations - Maurice Eastridge and Bill Weiss, Ohio State University Fact Sheet AS-0003-99 available on-line at http://ohioline.ag.ohio-state.edu/as-fact/0003.html verified 8-25-08


Corn Silage Management

Authors: Mark Sulc

Last week I posted three articles (one by Bill Weiss and two I wrote) about corn silage being ready for harvest in much of Ohio and how to determine dry matter content, see our blog http://ohioforages.blogspot.com/ for more information.

Below, I have listed each article individually.

Corn Silage Ready for Harvest in Ohio
http://ohioforages.blogspot.com/2008/08/corn-silage-ready-for-harvest-in-ohio.html

How to Determine Corn Silage Moisture
http://ohioforages.blogspot.com/2008/08/how-to-determine-corn-silage-moisture.html

Dry Forage Samples With a Hair Dryer
http://ohioforages.blogspot.com/2008/08/dry-forage-samples-with-hair-dryer.html

Late Season Emergency Annual Forages

Authors: Mark Sulc

Annual forages can still be planted in late August to early September to provide additional forage by early winter, assuming adequate rainfall is received. The best options for planting now are small grains and annual ryegrass.

Seedings should be made as soon as possible, to be completed no later than the first week September in northern Ohio and by Sept 10 to 15 in southern Ohio. Rainfall patterns will obviously have a big affect the success of late season forage plantings.

Forages planted this late in the season are best suited for utilization by grazing animals rather than mechanically harvested and stored. The lower yields from planting this late make mechanical harvesting questionable from an economic cost perspective, and poor drying conditions late in the year make the practical feasibility of mechanical harvesting questionable as well.

Oats seeded at 70 to 90 lbs per acre this late in the season have the potential to produce from 0.75 to 1.5 tons of forage dry matter per acre. Forage quality will be extremely high with late plantings (low NDF content and crude protein near 30%). Oats can be seeded no-till or into tilled seedbeds following wheat or corn silage harvest. No-till seeding is preferable for preserving precious soil moisture and to provide firm footing for grazing animals.

Oats can also be no-till seeded into existing perennial pastures that have been grazed short. This practice seems to work best when soil moisture is adequate for oat seed germination and oat growth, but not abundant enough for stimulating strong pasture regrowth. This may be the case this year, because we have dry soil conditions in many areas of the state. So we would need just enough rain to get the oats growing. The oats can add up to an extra ton of forage dry matter per acre in this manner.

Spring triticale can also produce well in the autumn like oats, but seed cost is much higher than for oats. Winter rye will produce limited forage this autumn and winter triticale will produce little to no forage this autumn, but both will produce significant forage early next spring. Winter wheat is not an option for autumn forage because of the need to delay planting until after the Hessian fly safe date. Mixtures of oats (60 to 70 lbs/acre) with a winter cereal (80 to 90 lbs/acre) such as winter rye, winter wheat, or winter triticale can provide both autumn and spring forage. The oat produces most of the autumn forage, and the winter cereal will produce the early spring forage.

Annual/Italian ryegrass is an option for planting by early to mid September. Italian ryegrass will most likely produce less forage than oats this autumn. However, a few Italian ryegrass varieties have the potential to survive our winters and produce additional forage next spring. Refer to the Ohio Forage Performance Trials for selecting annual ryegrass varieties (http://www.oardc.ohio-state.edu/forage2006/default.asp).

Annual/Italian ryegrass should be planted at 20 to 25 lbs seed/acre. Annual/Italian ryegrass planted in early September in Western Ohio has produced 0.3 to 1.0 ton of forage dry matter per acre by November to early December, and some varieties have yielded 3 to 6 tons of dry matter per acre the following year with N fertilization.

A word of caution with using annual/Italian ryegrass – it may not be the best option if a grain crop will be planted early next spring. Annual/Italian ryegrass can be hard to kill in early spring and it can become a weed in wheat.

Nitrogen applications are often needed for good production of these annual grass forages. Applying 100 lbs urea/acre is usually a good practice, except where there is reason to suspect significant levels of residual N are left in the soil. This may the case following corn silage this year, due to the dry summer conditions and if high nitrogen applications were made to the corn. If nitrogen carryover is suspected, do not apply additional N to these crops. Oats and annual ryegrass are good N scavengers, and excess N in the soil can result in accumulation of toxic levels of nitrates in the forage.

Corn and corn stover. Finally, don’t forget the opportunity to utilize residue from one of Ohio’s most important annual grasses, corn. One acre of corn stover can meet the nutritional needs of one mature beef cow for about a month. For more information, refer to the factsheet ANR-10-02 “Grazing Corn Residue”, available at OSU Extension offices and online at http://ohioline.osu.edu/anr-fact/0010.html. Standing corn can also be grazed directly by cattle (strip grazing only) and sheep with good results.

Managing Biennial and Perennial Weeds in Wheat Stubble

Authors: Mark Loux

The late summer and fall following wheat harvest can be an optimum time to apply herbicides for control of biennial and perennial weeds. Perennials can be classified as either warm-season or cool-season for the purposes of determining when to apply herbicides in the fall. Warm-season perennial species are those that die or are severely injured after the first frost in the fall. Examples of warm-season perennials include hemp dogbane, common milkweed, pokeweed, horsenettle, and johnsongrass. Cool-season perennials and biennials will survive several frosts and are typically still green into about early November. Cool-season perennials include quackgrass, curly dock, Canada thistle, and dandelions. Biennials that survive into late fall after their first season of growth include poison hemlock and wild carrot, and these are much more effectively controlled by fall herbicide treatments, compared with spring burndown treatments.

As a general rule, most effective control will occur when perennials are at least 8 to 15 inches tall at the time of herbicide application. Apply herbicide prior to the onset of plant senescence, or by about mid-bloom for any species that are flowering in the early fall. Fields should not be mowed from this point on, to allow perennials to grow to an appropriate size. For control of warm-season perennials, apply herbicides in mid-September or at least one week before a light frost. For control of cool-season perennials and biennials, apply between mid-October and early November. Control of cool-season perennials can be more effective when a light frost occurs prior to herbicide application.

We suggest applying a mixture of glyphosate and 2,4-D for most effective control of broadleaf biennial and perennial weeds. Exceptions to this include any field where perennial grasses or Canada thistle are the primary target, since glyphosate alone can adequately control these perennials, and the addition of 2,4-D can reduce the activity of glyphosate on these species. Glyphosate labels contain specific information on the rates required for control of many perennial species, and a quick review of this section of the label can help in decisions on rate. Our general recommendation for a mixed bag of perennial species is to apply the following: glyphosate @ 1.1 to 1.5 lb ae/A plus 2,4-D ester @ 0.5 to 1 lb ai/A. The higher rates can result in more effective control of the harder to control perennial weeds, and also perennial grasses. However, Canada thistle and quackgrass can be effectively controlled by glyphosate applied alone at the rate of 0.75 lbs ae/A, when applied in a spray volume of 10 gpa or less. Include ammonium sulfate at recommended rates. Additional information can be found on glyphosate labels, and in the “Problem Weeds” section of the “Weed Control Guide for Ohio and Indiana”. The bulletin can also be viewed online at https://agcrops.osu.edu/weeds.


Late-Planted Wheat After Soybeans, Back-to-Back Wheat or Wheat After Corn?

Authors: Dennis Mills, Pierce Paul

The prospect of a late soybean harvest again this year already has some Ohio wheat growers thinking about planting wheat after corn or wheat after wheat. Indeed, late planting may result in poor stand establishment (fewer tillers per foot of row) and increase winter kill. While planting back-to-back wheat will ensure that the crop is planted at the recommended time for adequate tiller development before winter dormancy, it increases the potential for disease and insect (Hessian fly) problems.

Wheat following corn. Being both members of the grass family, wheat and corn may be affected by some of the same pests and diseases. One such disease, and by far the one of greatest concern is head scab, caused by Fusarium graminearum. This fungus causes ear and stalk rot in corn and even if the cornfield into which wheat is planted did not have a major ear rot or stalk rot problem this year, the fungus still is present in the corn stubble left in the field after harvest. Wheat planted into this stubble is more likely to have head scab and vomitoxin problem next year, especially if late-spring, early-summer conditions are wet and humid. Our studies have shown that when residue is abundant (more spores of the fungus present), only a few days of wet and humid conditions during flowering are needed for head scab to develop and vomitoxin to exceed critical marketing thresholds (2 ppm). We had very little or no head scab problems in 2008 not because the disease is no longer a concern in Ohio or because our varieties are all resistant; it was largely because conditions were cooler than normal dry during flowering and because we practiced good crop rotation by planting wheat after soybeans instead of after corn or wheat. Remember, one of the best ways of minimizing losses due to head scab and vomitoxin is to plant wheat after soybeans and not after corn.

Wheat following wheat. Head scab is just as big a problem in wheat following wheat as it is in wheat following corn. The fungus survives equally well in both corn and wheat stubble. In addition, growers who plant wheat after wheat usually have more problems with diseases such as Cephalosporium stripe and Take-all root rot. Plants severely infected in the fall and winter will become weak and discolored in the spring and often die prematurely without producing grain. In addition, foliar diseases such as Stagonospora leaf blotch, Septoria leaf blotch, powdery mildew, and tan spot become more problematic when wheat follows wheat. These diseases are all caused by fungi that survive in wheat stubble left in the field, and as such, can readily attack the new crop and spread shortly after germination or early in the spring. When diseases become established early, growers are more likely to suffer higher yield and quality losses.

Effective fungicides and resistant varieties are available for controlling Stagonospora leaf and glume blotch, Septoria leaf blotch, powdery mildew, and tan spot. However, there is no variety that is resistant to, and no fungicide that is highly effective against, all of the potential disease problems associated with a wheat-on-wheat or a wheat-on-corn cropping system. Most of our varieties are susceptible to head scab and fungicides are less effective against this disease when spores are abundant (wheat and corn stubble present in fields) and weather conditions are favorable (wet and humid). Similarly, in the case of Take-all and Cephalosporium stripe highly resistant varieties are not available, so crop rotation (with soybeans or other legume) is still the best way to manage these diseases. A minimum of one to two years (two years better than one) away from wheat, barley or related grass species are needed for adequate control. Tillage to bury and speedup the decomposition of spore-bearing residue would be another good option to minimize disease problems in a non-rotational system. However, deep plowing alone will only minimize, but not eliminate any of these diseases.

Given the problems associated with planting back-to-back wheat or wheat following corn, growers would be better off sticking to the recommended practice of planting wheat after soybeans, even if it means planting wheat a little later than normal. If late planting becomes an issue, growers should plant at a higher seeding rate than the regularly recommended rate of 1.2 to 1.6 million seeds per acre for 7.5-inch rows (that is about 18 to 24 seeds per foot of row with normal sized seed) to compensate for fewer tiller development in late-planted wheat (during the third and fourth week after the fly-safe date). Plant at a rate of 1.6 to 2.0 million seed per acre instead. The number of seeds per pound and germination rate are important for determining the correct seeding rate and drill calibration. There are fewer seeds per pound of large seeds than per pound of small seeds. The number of seeds per pound can be found on the seed bag.

Soybean Seed and Pod Feeding Insects

Authors: Ron Hammond, Andy Michel, Bruce Eisley

During the later part of the summer, we usually receive reports of bean leaf beetles in late maturing soybeans in September; subsequently the fields end up having high levels of pod feeding. These soybeans can be late planted fields, double-cropped soybeans, and relay-intercropped soybeans. What ever the reason, these still-green soybeans act as trap crops for second generation bean leaf beetles, providing a food source prior to overwintering. In addition to these beetles, we often find high populations of grasshoppers, especially along field edges, that continue to feed on pods.

Because of past problems, we felt it important to caution growers of potential pod feeding by these two insects. Growers with fields that remain green well into September are advised to continue monitoring those fields until they begin to mature in mid to late September. Although leaf defoliation will not be a major concern, injury to the pod is a potential problem because of yield loss potential and seed quality issues. This concern is especially important with food grade soybeans and soybeans being grown for seed. If insect populations are high, still active and continuing to feed, and pod injury has reached 10% and is relatively new, an insecticide treatment is warranted to prevent further pod injury. Growers should be careful with their insecticide choice because of the shorter time period from application to harvest. See the following web sites, http://entomology.osu.edu/ag/545/siblb.pdf and http://bugs.osu.edu/ag/545/sigrass.pdf for a list of labeled materials for bean leaf beetle and grasshopper control, respectively, along with their pre-harvest intervals.

An additional group of insects to call your attention that feed on pods that are capable of causing severe injury to the seed are stink bugs. We often find three pest species in soybeans with the green stink bug being of most concern (the other two are the southern green stink bug and the brown stink bug). If finding a lot of the brown stink bugs in your field, make sure you do not confuse them with a fourth species of stink bug, the spined soldier bug, which has sharp-pointed shoulders. The one that is a pest, the brown stink bug, has a rounded shoulder. The spined soldier stink bug is a predator on other insects and is consider beneficial. Although not usually a problem in Ohio, we have received a few reports of higher than normal stink bug numbers in some fields. Growers, especially those in more southern regions of the state, should be aware of these insects because their feeding can result in discolored and smaller seeds. The threshold for the green stink, taken from Purdue’s field guide, ranges from 20 stink bugs per 100 sweeps for seed or food grade soybeans to 40 stink bugs per 100 sweeps for regular soybeans. Most of the insecticides labels for the bean leaf beetle or the soybean aphid are also labeled for stink bug control; read the various labels for rates.


Central Ohio Agronomy Day Program

Authors: Howard Siegrist

Central Ohio Agronomy Day program is set for Thursday, September 4, 2008 from 10 a.m. until 4 p.m. at the David Miller Farm, 10750 Millersport Road, Millersport, Ohio. The program will address significant issues and challenges facing grain producers in the Central Ohio area. Resources for the day will include Ken Ferrie, Farm Journal Magazine Agronomist. Mr. Ferrie will present information on how local growers can correct soil problems that were created by the heavy rains and flooding of the spring. Economizing on fertilizer dollars will also be addressed. Many of the sessions during the day will be hands on and in the field. Auto steer and “smart” equipment will be a part of your farming future with “Zone and Grid Soil Mapping” as a major part of the days demonstrations with more than seven companies and technology providers present. A special “ride or drive” opportunity will be provided from 3 p.m. until 4 p.m.

Other sessions will look at plant health programs, managing sky high fertilizer prices and making wise agronomic decisions for 2009 and a grain market review and analysis provided by OSU Grain Market Specialist, Matt Roberts.

The program cost is a $10.00 registration fee. No advance reservations are needed. The cost helps defray the expenses of the program. A free pork loin lunch will be provided. Certified Crop Advisor continuing education credits will be offered. The event is sponsored by the Pickaway, Fairfield, Perry and Licking county offices of OSU Extension. Additional information can be secured by accessing the following website at http://licking.osu.edu/agriculture/2008-central-ohio-agronomy-field-day or email siegrist.1@cfaes.osu.edu

The David Miller farm is located three miles south of I-70 and 1/2 mile south of the village of Millersport, Ohio. The farm can be accessed by exiting I-70 at the SR37 exit or the SR79 exit.

Ohio Soy Industry Insight Forums

Authors: Harold Watters

August 26, 2008 Owens Community College, Findlay
August 27, 2008 Champions Center (Clark County Fairgrounds), Springfield

Ohio Soybean Council is bringing together Ohio's soybean producers and industry
representatives to discuss today's trends and tomorrow's opportunities in
the soybean business. The 2008 Ohio Soy Industry Insights Forum promises to
be an interesting and informative event designed to give participants a
chance to gain a greater understanding of the soybean crop's value to the
ultimate end consumer.

Notable industry experts from Monsanto, Pioneer, ADM, and Farm Credit
Services of Mid America will conduct presentations on topics ranging from
future traits to risk management and new uses for soybeans. In today's
ever-changing marketplace, it's good business to continually learn about the
latest opportunities available at both the local and global levels. We
invite you to start planning for the future at the 2008 Ohio Soy Industry
Insights Forum.

Registration begins at 8:30 am with lunch served at 12:00 pm. The forum
will conclude at 3:30 p.m. CCA-CEU credits are: Crop Management 3.5 hours, Professional Development, 2.0 hours.

To register now for the event at the location near you call 866-748-6579 or
email us at pfarmer@soyohio.org.

Weather Update

Authors: Jim Noel

The outlook for this week: near normal temperatures. There should be rain over eastern and southern Ohio from the remnants of Fay as it lifts north and east. Expect 0.25 inches to over 1 inch in some areas of beneficial rain seems on tap especially east of I-71. The far western and northwest sections probably won't get much of anything. The heaviest rains will be in the far east and south as it appears now. Monitor later forecasts as there is enough uncertainty that most areas could get some rain to most areas don't get much at all. The mostly likely is described above. This would mostly occur Wednesday into early Thursday. A weak front may spark a few storms on Friday. After that, it looks dry until late next week when a few more showers would be possible.

Overall, near normal temperatures and below normal rainfall continues into Sept. for now until I see something change, but in those eastern and southern counties that get rains from Fay, that will mean near normal rainfall.

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), Peter Thomison (Corn Production), Mark Sulc (Forages), Mark Loux (Weed Science) and James Noel (NOAA/NWS/OHRFC). Extension Associates and Educators: Roger Bender (Shelby), Greg La Barge (Fulton), Steve Bartels (Butler), Harold Watters (Champaign), Mike Gastier (Huron), Tim Fine (Miami), Suzanne Mills-Wasniak (Montgomery), Todd Mangen (Mercer), Marissa Mullet (Coshocton), Mark Koenig (Sandusky/Ottawa), and Ed Lentz (Seneca).

About the C.O.R.N. Newsletter

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.