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September 10 to September 16,
2001
C.O.R.N. 2001-30
In This Issue:
A) Get Ready to Plant Wheat: Steps to Improved Yield
B) Effect of Row Spacing on Wheat Yield
C) Fall Herbicide Applications for Wheat
D) Weed Control in Wheat Stubble Fields
E) Corn Leaf Diseases and Stalk Rots
F) Drydown Rates in Corn and Potential for Harvest Losses
G) Time to Take Last Harvest of Forage Legumes
H) Multicolored Asian Lady Beetle
I) Visit the OSU Agronomic Crops Team at the Farm Science Review
and Receive a Free Gift
High yields and low cost production are necessary for wheat to be a viable economic partner in the crop-rotation sequence in Ohio. Wheat has a place in the rotation sequence on nearly every farm in Ohio, if for no other reason than to help reduce problems associated with continuous planting of soybeans and corn. The most prudent wheat production system is one of defensive management. High yield wheat research conducted over the past four years as On-Farm research plots and on OARDC research facilities have confirmed that high input wheat does not consistently improve economic returns on investment. However, consistent high yields can be obtained 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 to produce the best crop possible.
- Select high-yielding varieties with good straw strength and disease resistance. Do not jeopardize your investment by planting anything but the best yielding varieties that also have good resistance to yield robbing diseases like powdery mildew and Stagonospora blotch. Use good clean seed that has been treated with a fungicide to control seed borne diseases.
- Plant after the Hessian Fly Safe date for your county. Planting within the first 10 days after this date ensures the proper planting time to avoid serious insect and disease problems including Hessian Fly, Barley yellow dwarf virus and several foliar diseases. Early planting has reduced yield by 7.5 to 20% in research trials due to increase disease levels as compared to those planted after the Hessian Fly Safe Date.
- Optimum seeding rates for Ohio are between 1.2 and 1.6 million seeds per acre. For drills with 7 inch spacing between rows plant 16 to 21 seed per foot of row. In seeding rate studies conducted over the past four years, seeding rate had little effect on final yield. High seeding rates (above 30 seed/foot of row) increased lodging potential. There is no evidence that more seed is better, it only costs you more money.
- Planting depth is critical to winter survival and tiller development. Plant
seed 1 to 1.5 inches deep and make sure the seeding depth is uniform across
the field. Rough ground or heavy crop residues greatly affect planting depth
even with the newer no-till drills. Remember shallow planting is the main cause
of winter heaving and freezing injury to wheat causing thin stands in early
spring. Additionally, you can not compensate for a poor planting job by planting
more seed, it just costs you more money.
- Apply 20 to 30 lb of nitrogen prior to planting in the fall and apply the
rest of the nitrogen requirement for the crop as a top dress in the spring.
An application of nitrogen in the fall was one of the main factors that contributed
to consistent high yield in our recent research tests. Remember to subtract
the amount applied in the fall from the total crop requirement and apply the
difference in the spring as a single application between green up and beginning
stem elongation (mid March to early April).
- Apply Phosphorus and Potassium at planting time based on a soil test.
Remember to record the information and decisions you made including variety planted, planting date and weather conditions for future reference. Having accurate and complete notes will help you be a better manager and increases your chances of improving your profit margin.
A dense population of winter annual weeds can suppress wheat growth, especially in the spring when growth of the weeds and wheat resume. Application of herbicides in the fall can help manage winter annual weeds and prevent them from inhibiting crop growth in the spring. Chickweed, henbit, and marestail are already emerging in soybeans, and will continue to emerge throughout September and early October.
An application of glyphosate after soybean harvest and prior to no-till wheat planting will effectively control emerged winter annuals and control or suppress dandelion. Dicamba products should not be applied within 15 days before wheat planting and 2,4-D is not labeled for preplant application in wheat, so glyphosate is really the primary option for application between soybean harvest and a timely wheat planting. Winter annuals will be small at that time, and rates of 20 oz/A of Roundup Ultra Max (or 24 oz/A of Touchdown, Glyphomax, and other glyphosate products) should be adequate. Established dandelions will require a rate of 26 oz/A of Roundup Ultra Max (or 32 oz/A of Touchdown, Glyphomax, and other glyphosate products).
Several herbicides can be applied later in the fall to emerged wheat to control winter annuals if needed. Harmony Extra and Harmony GT can be applied in the fall to wheat that has reached the 2-leaf stage. Peak can be applied in the fall after wheat is in the 3-leaf stage, but double-crop soybeans cannot be planted following a wheat crop treated with Peak. Harmony Extra is more effective than Harmony GT and Peak when several different winter annuals are in the field. Sencor is labeled for postemergence application to wheat in the fall, but rate varies with wheat size and not all wheat varieties have adequate tolerance. We suggest consulting the Sencor label and your seed company for more information when considering use of Sencor.
If the field predominantly has warm-season perennials such as johnsongrass, milkweeds, hemp dogbane, and perennial nightshades, spray these fields from now until the first frost. A light frost on these type of species will kill them. Make applications to these weeds before too many leaves start to fall off the plant. If over 50 % of the leaves have fallen off the plant, then poor control may result due to lack of herbicide uptake. Try to apply herbicides during warm temperatures. Apply only glyphosate at 1.12 lb ae/A to control johnsongrass. For milkweeds, hemp dogbane, bindweeds, and nightshade species use glyphosate at least at 1.12 lb ae/A plus 2,4-D ester at 1.5 pt/A.
If the field predominantly has cold-season perennials, such as Canada thistle, quackgrass, and dandelion, applications should be made from mid to late-October. For Canada thistle and cool-season perennial grasses use only glyphosate at 1.12 lb ae/A. For dandelion, use 2,4-D ester at 1.0 qt/A or glyphosate 0.75 lb ae/A plus 2,4-D ester at 1.5 pt/A.
Make sure all perennial species are at least 8 inches tall, to allow for good root or rhizome kill. The bigger the plants are the better the long-term control of perennials. Decide what the predominant species are in the field, to determine when you should apply the herbicides in wheat stubble. Then choose the appropriate herbicide and rate for the species and size of weeds in the field.
Gray leaf spot has increased in severity in fields where it was detected earlier and susceptible hybrids have disease lesions to the top leaves in these fields. We have seen several other leaf diseases this year that may contribute to the overall premature loss of green leaf tissue at this time of year. These include anthracnose, common rust, northern leaf spot and northern corn leaf blight. All of these leaf diseases can contribute to rapid and premature death of the corn plant.
During the latter stages of grain fill the corn plant translocates carbohydrates and other nutrients out of the leaf and stalk tissues to fill the grain. Fungi attacking the leaves and stalks also utilize these nutrients and cause a more rapid and complete depletion of nutrients that would have been used to keep the stalk alive. When severe leaf blighting occurs the rapid depletion of food reserves in the plant predisposes the corn stalks to invasion by stalk rot fungi and rotting stalks become prone to lodging. Anthracnose stalk rot has been particularly common this year and the later season stalk rots like Gibberella and Diplodia have already been detected.
Plan now to visit all your corn fields to evaluate stalk quality. The process is simple. Check stalks by squeezing the lower stems to see if they are soft. By assessing 20 plants in four or five different areas of the field you can get a good assessment of the lodging potential. Plan to harvest those fields with the highest percentage of soft stalks first. Continue to monitor the stalk quality in fields as you progress through the harvest season. Stalk quality can change quickly, especially if anthracnose or Gibberella stalk rot are present early. Wet weather for a few consecutive days can profoundly reduce stalk quality and increase lodging in a field. Spending a few hours scouting your fields now can help put more of the corn in the bin and prevent grain loss in the field due to lodging.
The loss of one "normal" sized ear per 100 feet of row translates into a loss of more than one bushel/acre. In fact, an average harvest loss of 2 kernels per square foot is about 1 bu/acre! According to an OSU ag engineering study, most harvest losses occur at the gathering unit with 80% of the machine loss caused by corn never getting into the combine.
Corn will normally dry approximately 3/4 to 1% per day during favorable drying weather (sunny and breezy) during the early warmer part of the harvest season from mid-September through late September (probably a week to 10 days earlier, respectively, for southern and northern Ohio). By early to mid-October, drydown rates will usually drop to 1/2 to 3/4% per day. By late October to early November, field drydown rates will usually drop to 1/4 to 1/2% per day and by mid November, probably 0 to 1/4% per day. By late November, drying rates will be negligible.
Estimating drydown rates can also be considered in terms of Growing Degree Days (GDDs). It takes about 30 GDDs to lower grain moisture each point from 30% down to 25%. Drying from 25 to 20 percent requires about 45 GDDs per point of moisture. In September we generally average 10 to 15 GDDs per day. In October (as things cool down) the rate drops to 5 to 10 GDDs per day. However, note that the above estimates are based on generalizations, and it is likely that some hybrids vary considerably from this pattern of drydown.
We conducted evaluations of corn drydown at the OSU-OARDC Western Branch Research Farm, near S. Charleston, OH in 1991 and 1992. In 1991, under warm, dry fall conditions, grain moisture loss per day ranged from 0.76 to 0.92%. Whereas under cool, wet fall conditions in 1992, grain moisture loss per day ranged from 0.32 to 0.35%. Grain moisture losses based on GDD ranged from 24 to 29 GDD/percent moisture (i.e., a loss of one percentage point of grain moisture per 24 to 29 GDD) in 1991, whereas moisture loss ranged from 20 to 22 GDD in 1992. The number of GDDs required to reduce grain moisture was lower in 1992 than 1991.
For additional discussion of corn drydown check out a recent article prepared by Dr. Bob Nielsen, extension agronomist at Purdue - it's available on-line: http://www.agry.purdue.edu/ext/corn/news/articles.01/Grain_Drydown-0826.html
It is definitely time to wrap up the last harvest of the year for forage legumes. Harvest of forage legumes should be completed THIS WEEK. They should not be cut during the 6-week period before a killing frost. For our region, this means the period from mid-September through October is the critical fall rest period. Harvesting during this period disrupts accumulation of energy reserves and development of cold hardiness.
Late September and early October cutting can be especially stressful, but the injury suffered depends on the winter conditions which no one can predict. The damage can be severe, mild, or non-existent. Despite the known risk, each year growers harvest forages during the fall. This year rainy weather has delayed cutting schedules throughout the growing season for many producers, pushing back the time when the crop will be ready for a last harvest. Growers should carefully weigh the need for additional forage against the increased risk of stand injury from fall cutting. THE TONNAGE EXPECTED FROM A FALL CUTTING AND THE NEED FOR THE FORAGE SHOULD BE HIGH BEFORE CONSIDERING A CUTTING DURING THE CRITICAL FALL PERIOD.
When harvesting alfalfa in the fall, research has shown that several factors can moderate the risk of winter injury. These can be used to assess the risk associated with cutting specific alfalfa fields this fall:
- Young, healthy stands are less susceptible to winter injury due to fall harvesting than older stands. On the other hand, more future production potential is lost if a younger stand is injured from fall cutting.
- Forages in well-drained soils will be at lower risk of injury than those with marginal drainage. Fall cutting should not be attempted on soils prone to heaving! Removal of the cover greatly increases the potential for heaving injury.
- Length of harvest interval during the growing season is often more important than the date of fall cutting in determining alfalfa stand survival. For example, a 3rd cutting during the fall is less risky than a 4th or 5th cutting taken during the fall, because a 3-cut schedule allows longer intervals and better recovery between cuttings compared with a 4-cut schedule. Likewise, a growth interval of 45 days BEFORE a fall harvest will reduce the risk of injury compared with a pre-harvest growth interval of 35 days or less. The longer growth period allows more energy buildup before the fall harvest, and lessens the need for energy buildup after harvest.
- Maintaining optimal soil fertility levels (pH, P and K) is extremely important in keeping the stand healthy and reducing risks from added stresses like fall harvesting.
- Disease resistant and winter hardy varieties will lessen the risk of injury from fall harvesting.
- Alfalfa that was protected from potato leafhopper injury during the summer will be at lower risk than if leafhoppers caused severe injury. Any stress (like wet soils) that weakened the crop during the year can increase the risk of damage from fall cutting.
- Cutting AFTER a killing frost (25 F for several hours) in late October or early November can be an option for WELL-DRAINED SOILS! Leave a 6-inch stubble after late fall cutting. Cutting this late in the year prevents regrowth that burns up energy reserves; however late removal of plant cover increases the risk of frost heaving!!! I'll say it again: FALL CUTTING SHOULD NOT BE PRACTICED ON SOILS PRONE TO HEAVING.
- Do not harvest late summer seedings this fall.
The Multicolored Asian Lady Beetle has been and will be a topic of discussion as this insect moves later this fall from fields into over wintering sites. The IPM group at OSU is currently surveying Ohio residents to see what problems this insect has caused in the past and to see what tactics have been used to try to stop this insect from getting into their homes.
The IPM group will be conducting meetings at three locations in Ohio in the
next few weeks about the lady beetle problem. Information about the meetings
(including times and locations) can be found on the Ohio IPM website at:
http://www.ag.ohio-state.edu/~ipm/lady/lady.htm
This site also has information about the biology of the lady beetle and suggestions
about treatments to be used around the home to stop the
beetle's home invasion.
While at the Crops Team exhibit, take a few minutes to try a weed identification quiz, and look at displays on the soybean aphid, soybean cyst nematode, sudden death syndrome in soybeans, and weed resistance in Ohio. Displays from the OSU Extension Precision Agriculture Team will also be at the same location.
Readers can subscribe electronically to this newsletter by sending an e-mail message to: corn-out-on@postoffice.ag.ohio-state.edu. A successful subscription message will receive by an automatic reply from the listserv. Contact your local Ohio State University Extension Office or e-mail labarge.1@osu.edu if you have problems subscribing.
Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/
C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.
Contributors to C.O.R.N. this week include: State Specialists: Pat Lipps, Anne Dorrance and Dennis Mills (Plant Pathology), Peter Thomison (Corn Production), Ron Hammond and Bruce Eisley (IPM), Mark Loux and Jeff Stachler (Weed Science), Jim Beuerlein (Soybeans and Small Grains), Mark Sulc (Forages), and Ed Lentz (Northwest District Agronomist) Extension Agents: Barry Ward (Champaign), Dennis Baker (Darke), Greg LaBarge (Fulton), Howard Siegrist (Licking), Jim Skeeles (Lorain), Glen Arnold (Putnam), Ray Wells (Ross), Clark Hutson (Seneca), and Roger Bender (Shelby)Editor: Andy Kleinschmidt Web Editor: Tom Rosati
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868
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