C.O.R.N. Newsletter 2007-29

Dates Covered: 
September 4, 2007 - September 10, 2007
Editor: 
Andy Kleinschmidt

Bean Leaf Beetle, Pod Feeding, and Late Maturing Soybeans

Authors: Ron Hammond, Bruce Eisley

Although we mentioned it a few weeks ago, we thought it important enough to again remind growers about late season pod feeding by bean leaf beetle. Just this week, we have received reports of large second generation adult populations. Growers are strongly advised to continue monitoring soybean fields that remain green and succulent throughout September for the presence of bean leaf beetles. Adult beetles that emerge from yellowing soybean fields will move to those that are still green to continue feeding prior to overwintering. This movement will result in abnormally high densities in some late maturing fields.

Although defoliation will no longer be the major worry, injury to the pod will be of primary concern because of potential yield and seed quality losses. This concern is especially important with food grade soybeans and those being grown for seed, both situations where seed quality is an issue. However, regular fields that still filling pods will also be at risk for yield losses. If populations are high, beetles are still active and continuing to feed, and pod injury has reached 10-15% and is relatively new feeding, treatment is warranted to prevent further pod damage. Growers should be careful with their insecticide choice because of the shorter time period from application to harvest. See the following web site, http://entomology.osu.edu/ag/545/siblb.pdf for a list of labeled materials along with their pre-harvest intervals.

Important Management Guidelines for Wheat in Ohio

Authors: Dennis Mills, Pierce Paul, Edwin Lentz, Jim Beuerlein

The 2007/2008 winter wheat season is fast approaching and as growers make preparation for planting, we would like to remind them of a few important management decisions that are important for a successful crop. Nearly every farm in Ohio has a field or two that could benefit from planting wheat, if for no other reason than to help reduce problems associated with continuous planting of soybeans and corn. Consistent high yields can be achieved by following a few important management guidelines. Below are listed the most important management decisions that Ohio wheat producers need to make at fall planting time to produce a crop with satisfactory economic returns.

1) Select the right variety. Select high-yielding varieties with high test weight, good straw strength and adequate disease resistance. Do not jeopardize your investment by planting anything but the best yielding varieties that also have resistance to the important diseases in your area. Depending on your area of the state, you may need good resistance to powdery mildew, Stagonospora leaf blotch, and/or leaf rust. Avoid varieties with susceptibility to Fusarium head scab. Plant seed that has been properly cleaned to remove shriveled kernels and treated with a fungicide seed treatment to control seed-borne diseases.

2) Plant at the right time. Plant after the Hessian Fly Safe date for your county. This date varies between September 22 for northern counties and October 5 for the southern-most counties. Planting within the first 10 days after this date insures the proper planting time to avoid serious insect and disease problems including Hessian Fly, aphids carrying Barley Yellow Dwarf Virus, and several foliar diseases. Planting before this date has lowered yield by 7 to 20% in research trials due to disease and insect problems. On the other hand, planting late (generally after Oct 20 in northern Ohio) can reduce the number of primary tillers that develop in the fall and increases the risk of cold temperature injury.

3) Use the correct seeding rate. Optimum seeding rates are between 1.2 and 1.6 million seeds per acre. For drills with 7.5 inch row spacing, this is about 18 to 24 seeds per foot of row with normal sized seed. When wheat is planted on time, actual seeding rate has little effect on yield, but high seeding rates (above 30 seeds per foot of row) increase lodging. There is no evidence that more seed is better, it only costs more money.

4) Plant seeds at the right depth. Planting depth is critical for tiller development and winter survival. Plant seed 1.5 inches deep and make sure planting depth is uniform across the field. No-till wheat into soybean stubble is ideal, but make sure the soybean residue is uniformly spread over the surface of the ground. Shallow planting is the main cause of low tiller numbers and poor over-winter survival due to heaving and freezing injury. Remember, you can not compensate for a poor planting job by planting more seeds; it just costs more money.

5) Apply 20 to 30 lb of actual nitrogen per acre at planting to promote fall tiller development. Wheat also requires at least 45 ppm of available phosphorus per acre in the soil to produce really good grain yields. If the soil test indicates less than 40 ppm, then apply 80 to 100 pounds of P2O5 at planting. Soil potassium should be maintained at levels of 135, 165 and 185 ppm for soils with cation exchange capacities for 10, 20, or 30, respectively. If potassium levels are low, apply 60 to 100 pounds of K2O at planting. In Ohio, limed soils usually have adequate calcium, magnesium and sulfur for wheat. Soil pH should be between 6.5 and 7.0.

The key to a successful wheat crop is adequate and timely management. The above recommendations are guidelines that may be fine-tuned by you to fit your farming operation and soils. They also assume that you are planting wheat in fields that are adequately drained. You can review more details on these, and other, research-based wheat management recommendations on-line at
http://ohioline.osu.edu/iwy/index.html.

The Importance of the Preemergence Glyphosate Application in No-till Wheat

Authors: Mark Loux

Many winter weed problems in no-tillage wheat can be managed with a preplant/preemergence application of glyphosate. Dandelion and winter annual weeds such as chickweed and purple deadnettle have been problems in wheat in recent years. Producers are often not aware that these weeds are a problem until late fall or early spring. However, many winter annual weeds have emerged by early October and are easily controlled with relatively low rates of glyphosate prior to wheat planting. This can be a more effective treatment for winter annuals, compared to the herbicides that can be applied broadcast to wheat in late fall or early spring. Preplant glyphosate application is also by far the most effective and least expensive tool to control dandelion and winter annual grasses such as downy brome and cheat. A dense population of winter annuals or dandelion may have already suppressed wheat growth by the time a spring treatment can be applied.

Dandelion is especially problematic because most postemergence wheat herbicides have limited effectiveness on this weed. Dandelion should be controlled with tillage or glyphosate prior to wheat emergence, since options after emergence are less effective. Tillage must be thorough enough to completely disrupt dandelion plants, and this may not be accomplished with one pass of an implement designed primarily for seedbed preparation. Therefore, consider a glyphosate application prior to tillage for most effective dandelion control. We suggest a glyphosate rate of at least 0.75 lb of glyphosate acid per acre in any field that contains dandelion. Include ammonium sulfate in glyphosate treatments, and the appropriate amount of surfactant if specified by the product label. The activity of herbicides on dandelions may be reduced where fall dandelion growth has been less than vigorous as a result of dry conditions. Also, the preplant herbicide application timing for wheat is somewhat earlier than the optimum timing for fall dandelion control. However, we believe the control attained by a glyphosate application makes it worth the effort even if dandelions are not in the optimum condition. It is possible that increasing the glyphosate rate to 1.1 or 1.5 lbs of glyphosate acid per acre may improve dandelion control prior to wheat planting.

We usually at this time of the year start to receive questions about the safety and legality of 2,4-D applied prior to wheat planting. We do not know of any 2,4-D product labels that support this use of 2,4-D. There is some risk of stand reduction and injury to wheat from preplant applications of 2,4-D. We question why producers would want to use 2,4-D, when glyphosate can be applied for about the same cost to obtain a similar level of weed control (better on some species). One argument in favor of the use of 2,4-D would be to avoid overuse of glyphosate and slow the development of herbicide resistance. However, 2,4-D can be used with glyphosate in fall and spring herbicide treatments prior to corn and soybean planting, and would probably be best avoided prior to wheat planting.

Producers who have applied glyphosate at the time of no-till wheat planting report that their fields have been relatively free of winter annuals in the spring. However, producers also indicate that they often do not have time to make the application, given the time required to harvest corn and soybeans and plant wheat. Consider having the glyphosate custom applied where time is a limiting factor, especially in fields where winter weeds are evident. Where possible, apply the glyphosate several days before tillage or planting. Otherwise, be sure to apply before the wheat emerges!

Problems with Planting Wheat After Wheat or Wheat After Corn

Authors: Dennis Mills, Pierce Paul

High grain prices have Ohio wheat growers considering planting more wheat this fall. To increase their wheat acreage, some growers are thinking about planting back-to-back wheat crops. In addition, with more corn planted in 2007 and the prospect of a late soybean harvest again this year, some growers are even thinking about planting wheat after corn. Late planting may result in poor stand establishment (fewer tillers per foot of row) and increase winter kill. Some growers who had to deal with these problems last year and are concerned about facing a similar situation again this year may be considering planting wheat into the wheat fields they just harvested. While this will ensure that wheat is planted at the recommended time for adequate tiller development before winter dormancy, it increases the potential for disease and insect (Hessian fly) problems. So, from a disease management standpoint, which is worse? Wheat following wheat or wheat following corn?


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 2006 and 2007 not because the disease is no longer a concern in Ohio or because our varieties are resistant; it was because conditions were warm and dry during flowering in both years 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 beans 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 blotch, Septoria leaf blotch, powdery mildew, and tan spot. However, most of our varieties are susceptible to head scab and no fungicide is effective enough 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. Deep plowing alone to destroy stubble will 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. Use this information along with the table provided in the C.O.R.N newsletter “Correct Wheat Seeding Rates Can Increase Profit” by Jim Beuerlein (2005-29: September 6, 2005, http://corn.osu.edu/story.php?setissueID=102&storyID=605) to determine the amount of seed needed to plant 1.6 to 2.0 million seeds per acre.
 

Stalk Rot and Lodging in Corn: Potential Problem in 2007?

Authors: Peter Thomison, Pierce Paul, Dennis Mills

Hot, dry weather has plagued many corn fields throughout the growing season. Drought conditions experienced during grain fill often increase the potential for lodging and stalk rot 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 and 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.
 

Sampling Fields for Soybean Cyst Nematode

Authors: Anne Dorrance, Dennis Mills

Soybean cyst nematode is still a pest in many of Ohio's production fields. Light infestations of SCN in fields will have no above ground symptoms, which is part of the challenge, but yields will be anywhere from 5 to 10 bushels off. Higher infestations on susceptible soybean cultivars will have more severe symptoms, such as: soybeans will be irregular in height, mixtures of tall and short soybeans, early yellowing and very low yields. This pest is best managed with crop rotation, which reduces the SCN population levels and planting resistant cultivars. However, SCN readily adapts to ALL sources of resistance so it is important to manage the type of resistance that is planted in a field. The correct management plan starts with knowing what level of infestation is present.

The best time to sample fields for soybean cyst nematode is in the fall after the soybeans are harvested. Soybean cyst nematode populations can increase as much as 10 to 30 fold per growing season. Soybean cyst nematodes will not be distributed evenly throughout a field. Techniques for sampling soil for SCN by the Soybean Cyst Nematode Coalition are as follows:

1. Use a one inch diameter soil probe to collect samples (6-8 inches in depth)

2. Following a zig zag pattern, collect 10 to 20 soil cores per 10 to 20 acres

3. Collect cores from areas of similar soil type and crop history

4. Dump cores from each 10 to 20 acre area into a bucket or tub and mix thoroughly

5. Place 1 pint (2 cups) of mixed soil in a soil sample bag or plastic zippered bag and label with a permanent marker; and

6. Store sample in cool, dark place until shipped to the lab doing SCN analysis.

This level of sampling is necessary to obtain relatively accurate counts of the nematode population (egg and cyst) and to make meaningful recommendations for management. Charges this year at the C. Wayne Ellett Plant & Pest Diagnostic Clinic are $15.00 for each soil sample. Forms to accompany samples can found at the county extension offices or online at:
http://ppdc.osu.edu/8-30-Nematode.pdf

Mail samples to:
C. Wayne Ellett Plant & Pest Diagnostic Clinic
Room 110, Kottman Hall
2021 Coffey Road
The Ohio State University
Columbus, OH 43210

Additional Ohio SCN testing labs:
Brookside Laboratory Inc
308 S Main St
New Knoxville, OH 45871
Phone: (419) 753-2448
Fax: (419) 753-2949
Email: mflock@blinc.com
Cost: $13.00 per sample
Results reported: egg and cyst counts per 100cc of soil

Geophyta Inc
2685 CR 254
Vickery, OH 43464
Phone: (419) 547-8538
Fax: (419) 547-8538
Email: nathan@geophyta.com
Cost: $15.00 per sample
Results reported: cyst counts per 100cc of soil
 

Farm Pesticide Disposal

Authors: Roger Bender

The Ohio Department of Agriculture and The Ohio State University Extension will sponsor a farm pesticide disposal drop-off on September 12th from 9:30 a.m. – 3:30 p.m. at the Osgood American Legion Parking lot, located on Yorkshire-Osgood Rd. just South of St. Rt. 705.

The Clean Sweep program is designed to protect consumers and the environment. Ohio farmers can protect the environment by properly disposing of unusable and out-of-date pesticides.

The pesticide collection and disposal service is free of charge, but only farm chemicals will be accepted. Paint, antifreeze, solvents, and household and non-farm pesticides will not be accepted.

The pesticide collections are sponsored by the department in conjunction with the United States Environmental Protection Agency. To pre-register or for more information please contact the Ohio Department of Agriculture Pesticide Section at 614-728-6987.

Pesticide disposal collections have been conducted since 1993 with over one million total pounds collected and over 24,500 pounds collected just last year.

Farm Science Review CCA College Registration Ending September 7th

Authors: Harold Watters

The Certified Crop Advisor College at The Ohio State University Farm Science Review will be held Thursday, September 20, 2007 on the FSR grounds near London, Ohio. This program is sponsored by the OSU Agronomic Crops Team.

Topics this year include:
Balancing nutrients – manure AND commercial fertilizer
- Brad Joern, Purdue Extension Agronomist
- Robert Mullen, OSU Extension Soil Fertility Specialist

Challenges of growing corn in 2007
- Bob Nielsen, Purdue Extension Corn Specialist
- Peter Thomison, OSU Extension Corn Specialist

Corn disease management – a new era?
- Pierce Paul, OSU Extension Corn & Small Grains Plant Pathologist
- Greg Shaner, Purdue University Plant Pathologist

Cost: $70 which includes:
- Breakfast buffet and lunch
- Ticket to the Farm Science Review along with parking pass
- Additional tickets to the Farm Science Review are available for $5 when you register

Registration deadline is September 7th.
- Registration is limited - logistics prevent us from accepting late registrations!
- You will receive your parking pass and entry ticket only if registered by September 7.
- There is no on-site registration the day of the event.

Ways to register!
1. Internet: Get the registration form http://champaign.osu.edu/ag/ag.htm
Click on CCA College, print off, add check and mail to OSU Extension Champaign County.

or

2. Request registration form: Call OSU Extension, Champaign County at (937) 484-1526

Payment: Checks only are accepted, payable to OSU Extension and mailed to: OSU Extension – Champaign County, 1512 South US 68, Suite B100, Urbana OH 43078

CCA-CEUs (approved for 1.5 CM, 1.0 PM, 1.5 NM)

Water Resources Outlook

Authors: Jim Noel

The Water Resources Outlook for September has been issued by Tom Rench. It calls for continued drought in Tennessee and Kentucky into parts of southwest Ohio and southeast Indiana. It also calls for above normal streamflows across parts of northern Indiana into northern Ohio into northwest Pennsylvania. That area will remain close to the jet stream. Ohio into Indiana will be near the center of very quick changes across a sohrt distance.

For more details visit our Water Resources Outlook site at:

http://www.weather.gov/ohrfc/WRO.shtml

Jim Noel is a Senior Hydrologist with NOAA/NWS/OHRFC.

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Peter Thomison (Corn Production), Mark Loux and Jeff Stachler (Weed Science), Ron Hammond and Bruce Eisley (Entomology) and Jim Beuerlein (Small Grain Production), and Robert Mullen (Soil Fertility). Extension Educators: Harold Watters (Champaign), Steve Prochaska (Crawford), Glen Arnold (Putnam), Roger Bender (Shelby), Harold Watters (Champaign), Howard Siegrist (Licking), Steve Bartels (Butler), Mark Koenig (Sandusky), Wesley Haun (Logan), Ed Lentz (Seneca), Mike Gastier (Huron), Jonah Johnson (Clark), Mark Koenig (Sandusky/Ottawa), and Todd Mangen (Mercer).

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.