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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2005-29

Dates Covered: 
September 6, 2005 - September 12, 2005
Andy Kleinschmidt

Monitor Corn Maturation and Drydown

Authors: Allen Geyer, Peter Thomison

High temperatures, drought conditions, and premature plant death have accelerated maturation in many Ohio corn fields. A preliminary assessment (made Fri. 9-3-05) of the maturity of hybrids entered in the Ohio Corn Performance Test at the OSU-OARDC Western Branch (planted May 9) near S. Charleston, OH indicated that most hybrids in the early maturity trial (110 days or earlier) were at black layer (physiological maturity) with grain moistures at 29.2% and higher. Hybrids in the full season trial (111 days or later) varied from black layer to 1/2 milk line with grain moistures at 29.4% and higher.

Agronomists generally recommend that harvesting corn for dry grain storage should begin at about 24 to 25% grain moisture. Allowing corn to field dry below 20% risks yield losses from stalk lodging, ear rots, and insect feeding damage. This year growers should be prepared for localized root lodging and stalk lodging that may slow harvest and contribute to yield losses.

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. 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 dry down 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 dry down rates can also be considered in terms of Growing Degree Days (GDDs). Generally, it takes 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 average about 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 from this pattern of drydown.

Some of our past research evaluating corn drydown provides insight on effects of weather conditions on grain drying. During a warm, dry fall, grain moisture loss per day ranged from 0.76 to 0.92%. During a cool, wet fall, grain moisture loss per day ranged from 0.32 to 0.35%. Grain moisture losses based on GDDs ranged from 24 to 29 GDDs per percentage point of moisture (i.e., a loss of one percentage point of grain moisture per 24 to 29 GDD) under warm dry fall conditions, whereas under cool wet fall conditions, moisture loss ranged from 20 to 22 GDD. The number of GDDs associated with grain moisture loss was lower under cool, wet conditions than under warm, dry conditions.

Hurricane Katrina and Soybean Rust

Authors: Anne Dorrance

I thought I would give an update on what has been found in the Southern US, and what might have or have not happened last week with the storm. But first: There is absolutely no need for fungicides to be used on these soybeans, both full season or double crop. And here is why: There is soybean rust in the southern US, Florida, Georgia and Alabama. It is still difficult to find in the kudzu, but it can be found -- as you look at a patch of kudzu -- on a few of the oldest leaves there can be a lot of lesions, but nothing on the new foliage.

The soybean rust prediction models predicted that a very low number of spores may have been picked up by this hurricane and some may have reached Ohio. Estimates are in the range of 40 spores per acre; but not every spore will be successful, so we are down around 20 or less spores per acre. It will take 10 days for these spores to produce a lesion and more spores. Although, it will be next to impossible to find these few lesions in an acre of soybeans. However, similar to following hurricane Ivan, we might be able to find rust in Ohio around the first week of October. This will be after 3 to 4 cycles of increase – what will happen, will be a small area of a field with a few lesions. This information will be important to verify this model. This will also help us determine how much inoculum will be required in the southern US to have a major impact on us in the north. The soybeans in the state have begun to mature, so there will be fewer fields with green leaves by this time, but as you are traveling please make notes of those fields that will still be green in late Sept. and into October. If we do find rust then we will host a number of training sessions so everyone can visually observe rust on soybean plants. Also, we will be at Farm Science Review, so please bring any suspicious spots to the Soybean Rust Exhibit and we will check leaves. Have the bags labeled with the county and contact information.

Fall Herbicide Treatments - How They Fit Into Overall Weed Management Plans: Part I

Authors: Mark Loux

Fall herbicide treatments have become a fairly common practice for some no-till producers, who recognize their value for managing certain tough winter weeds and providing a weedfree seedbed in the spring. In previous falls’ C.O.R.N. articles on this subject, we have listed what we feel to be the most effective treatments based on our research. This list remains essentially unchanged between last fall and this fall, and it includes:

Any crop next spring-
Glyphosate + 2,4-D

Soybeans next spring-
Glyphosate + 2,4-D
CanopyEX + 2,4-D
Sencor + 2,4-D (excluding dandelions)

Corn next spring-
Glyphosate + 2,4-D
Simazine + 2,4-D
Basis + 2,4-D

Other herbicides (Valor, Scepter, Python, Aim, etc) can be applied in the fall, but most of these will not effectively control winter weeds unless they are combined with one of the herbicide treatments listed above. Effective control in the fall can be obtained with treatments costing $5 to $10 (excluding application cost), and we question the value of treatments that cost more than $10. For control of winter annual weeds, apply herbicide anytime after early October. For the most effective dandelion control, delay application until after a frost. We have applied as late as early December for control of winter annual weeds, but we generally recommend application when dandelions are still mostly green, or by mid-November if possible. Apply glyphosate-containing treatments with ammonium sulfate, and additional nonionic surfactant if specified by the product label. Treatments that do not contain glyphosate should generally be applied with crop oil concentrate for best results.

What we have not addressed in previous articles is where fall treatments fit in the overall weed management plan, and at what point in the crop cycle residual herbicides are best applied. Some reminders on what we are trying to achieve in no-till crops with weed management programs. First, the program has to control winter annual, biennial, and perennial weeds that emerge the previous fall or are already present at the end of the previous crop’s harvest. Weeds in this category include chickweed, purple deadnettle, marestail, wild carrot, and dandelion, among others. These weeds overwinter and regrow in the spring, interfering with crop establishment and early-season growth, and they need to be controlled by a fall or early-spring herbicide application. A secondary goal is to prevent seed production by these weeds, which prevents increased problems in the future. The other group of weeds for which control is essential includes summer annuals, such as ragweeds, foxtails, lambsquarters and black nightshade, and warm-season perennials, such as johnsongrass, milkweeds, and perennial vines. The early-emergers of these weeds can interfere with crop establishment, but the weeds in this group mostly compete directly with the crop during the growing season.

Current weed problems in soybean production lead us to believe that producers take advantage of the full benefits of residual herbicides (Canopy, Sencor, Valor, Scepter, etc) by applying them in the spring, rather than in the fall. Use of residual herbicides in the spring accomplishes the following in soybeans (both Roundup Ready and conventional): controls or helps control weeds that are problematic for glyphosate and other postemergence herbicides – marestail, giant ragweed, lambsquarters; reduces early-season weed competition so that soybean yield is not reduced if postemergence herbicide application is delayed; creates a wider window for postemergence herbicide application; and allows slightly later postemergence application to control later-emerging summer annual and warm-season perennial weeds. Residual herbicides are especially helpful in situations where the soybean canopy is slow to develop, because this tends to allow late emergence of weeds that are not suppressed by the crop.

Marestail, lambsquarters, and giant ragweed have been especially problematic in Roundup Ready soybeans in recent years. Our primary recommendation with regard to management of these weeds is the use of a combination of preplant (residual) and postemergence herbicides, and the residual herbicides will generally be most effective when applied in the spring. Many preemergence soybean herbicides can provide season-long lambsquarters control when applied in the spring. Marestail control may be more variable than lambsquarters with residual herbicides, but our research shows that spring applications are much more effective than fall applications for control of marestail that emerge into June. With regard to giant ragweed, which emerges well into June, one hopes that residual herbicides control at least some of the early emergers and slow down its growth rate, so that the postemergence herbicides are applied to relatively small plants. The most effective residual herbicides on giant ragweed are CanopyEX. SynchronyXP, Scepter, FirstRate/Amplify, and Gangster, although the effectiveness of all of these can be limited in ALS-resistant ragweed populations.

Next week: Part 2 of this article describing the pros and cons of various approaches to the use of residual herbicides in fall and/or spring.

Getting That Last Cutting of Alfalfa

Authors: Mark Sulc

Early September is ideal for taking that last yearly cutting of alfalfa. The timing of this cutting can be very important to the long-term health of the stand. It is best for alfalfa to not be cut during the 5 to 6 week period before a killing frost. During this critical period, cold resistance and energy reserves for winter survival are built up.

A killing frost for alfalfa occurs when temperatures drop to 25F or less for several hours. So the period from mid-September through October is the critical fall rest period in our region. Harvesting during this period disrupts accumulation of energy reserves and development of cold hardiness.

Producers often harvest alfalfa during the critical fall period despite the increased risk of winter injury. Research shows that often the tonnage gained by cutting during the critical fall period is lost in the first cutting the following year. Plus there is the increased risk of winter injury and ultimately shorter stand life by stressing alfalfa in this way.

The tonnage expected from a cutting and the need for the forage should be high before considering a cutting during the critical fall period.

When harvesting alfalfa during the critical fall period, several factors can help reduce the risk of winter injury:

1. Young, healthy stands are less susceptible to winter injury from fall harvesting than older stands. On the other hand, more future production potential is lost if a younger stand is injured from fall cutting.

2. 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 topgrowth cover increases the potential for heaving injury.

3. Length of harvest interval during the growing season is often more important than the actual date of fall cutting. Making a 3rd cutting during the fall is less risky than making a 4th cutting in the fall, because a 3-cut schedule allows longer intervals for plant 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 30 days. The longer growth period allows more energy buildup before the fall harvest, lessening the amount of energy reserves needing to be built up after harvest.

4. Fields with optimal soil fertility levels (pH, P, K) are at less risk than where fertility levels are lower.

5. Disease resistant and winter hardy varieties lessen the risk of injury from fall cutting.

6. Alfalfa that was not under stress during the summer will be at lower risk. Any stress (wet soils, potato leafhopper injury, etc) that weakened the crop during the year can increase the risk of damage from fall cutting.

7. Cutting AFTER a killing frost (25 F for several hours) in late October or early November can be an option for well-drained soils only. Leave a 6-inch stubble after late fall cutting. Cutting this late in the year prevents regrowth that burns up energy and protein reserves; however late removal of plant cover increases the risk of frost heaving! Fall cutting should not be practiced on soils prone to heaving.

Bean Leaf Beetle on Late Maturing Soybeans

Authors: Ron Hammond, Bruce Eisley

We continue to receive reports of large bean leaf beetle numbers on later planted soybeans that are in the late R5 stages, where seeds are still filling the upper pods. These fields or areas within the fields have significant levels of defoliation and are beginning to see pod injury. Growers are advised to continue monitoring those soybean fields that are still green for the presence of bean leaf beetles. Although defoliation is no longer the major worry, injury to the pod is a concern because of both yield and quality loss. If populations are still high, beetles appear active and are continuing to feed, and pod injury is reaching 10-15% and is relatively new feeding, treatment might be warranted to prevent further pod damage. Growers should be careful with their insecticide choice because of the shorter time period from application to harvest.

Wheat Planting and Hessian Fly Safe Date

Authors: Ron Hammond, Pierce Paul, Jim Beuerlein

Wheat growers are reminded to plant their wheat after the Hessian Fly Safe date for your county. The following web site gives the fly safe date for all of Ohio:

These dates vary beginning on September 22 for northern counties to October 5 for the southern most counties. Planting within the first 10 days after this date ensures the proper planting time to avoid not only problems from the Hessian fly, but also disease problems from barley yellow dwarf virus and several foliar diseases. Planting before these dates has lowered yield by 7 to 20% in research trials due to diseases and insect problems.

Correct Wheat Seeding Rates Can Increase Profit

Authors: Jim Beuerlein

Many of the wheat seed fields harvested this spring had long grain fill periods which resulted in large seeds for planting this fall. Normally, there are fourteen to sixteen thousand wheat seeds per pound, but many of the seed lots we will plant this fall have only ten to thirteen thousand seed per pound. Although the number of seeds per foot of row is the same as in previous years, the pounds of seed per acre will be greater this fall.

Calibrate the drill for each variety and each seed lot planted. The optimum seeding rate is 1.2 to 1.6 million seeds per acre for 7.5-inch rows when planting during the two weeks following the fly-safe date. During the third and fourth week after the fly-safe date, plant 1.6 to 2.0 million seeds per acre. Do not plant faster than the speed at which the drill was calibrated. The number of seeds per pound and germination rates are critical factors that need to be known before the proper seeding rate can be determined and the drill calibrated. That information should be listed on the bag of seed. The following table shows the pounds of seed needed per acre to accomplish various seeding rates using different sizes of seed.

Pounds of Seed Needed to Plant from 1.2 Million to 2.0 Million
Seeds Per Acre with Different Size Wheat Seed


------ Millions of Seed Per Acre------

SeedsPer Pound





























































Sustainable Ag Field Day

Authors: Alan Sundermeier

September 8, 2005 from 6:30 - 8:30 pm in Wood County at the Ag Incubator Foundation 13737 Middleton Pike road (St. Rt. 582). Directions: 5 miles north of Bowling Green, OH , take St Rt. 582 1/2 mile west of St. Rt 25. Free and open to the public. Topics of Interest: Organic corn variety plot; Soybean aphid organic spray plot; Farming systems experiment - organic, reduced input, and no-till grain production, kitchen incubator and canning facility tour, aquaculture research project, mobile solar energy demonstration, naturally native nursery gardens. For more information contact Alan Sundermeier at 419-354-9050.

"Pre-Harvest Tune-Up" Field Day Planned at Farm Focus

Coming up on Monday, September 12, 2005, the Farm Focus committee in conjunction with Ohio State University Extension and the Ohio Agricultural Research and Development Center (OARDC) will host a Field Day at the Marsh Foundation Farm (Farm Focus site) in Van Wert, Ohio. The chosen topic “Pre-harvest Tune-up” will encompass a number of activities aimed at getting farmers ready for fall harvest, and all the field work that follows harvest.

Registration for the afternoon activities begins at 12:30 p.m. Visitors will want to arrive on time so they have an opportunity to participate in all the events. Planned activities include combine clinics, a fall weed control workshop, and wagon tours of the various research plots at Farm Focus.

Local implement dealers will have their combine technicians on hand to walk farmers through a checklist of things they can do to make sure their combines are set properly to achieve the most efficient and effective harvest of their corn and soybeans. John Deere and Case IH will be represented and possibly other makes as well.

With the increase of no-till and reduced tillage conservation practices, learning to deal with increased weed pressures from a number of persistent perennials and winter annuals is becoming an issue for farmers. Dr. Mark Loux, OSU Extension weed specialist, will be at Farm Focus to talk about fall herbicide options available to help control these weeds. According to Dr. Loux, fall herbicide applications for some of these species can be more effective from both a control and cost standpoint than spring applications.

One of the most popular events at past Farm Focus shows was the wagon tours of the research plots. This tradition will be continued at the September 12th field day. Visitors will have the opportunity to see and hear about some of the newest products and technology available in agriculture as they ride past the 18 different trials at the site. There are studies on corn row spacing and population, crop rotations, insecticides and fungicides for soybeans, fertilizer programs utilizing animal waste, foliar fertilizers, weed control for non-GMO corn and soybeans, and many others.

Additional financial sponsorship of the Farm Focus Field Day is being provided by several local agribusinesses. These include Farm Credit Services; Kennedy-Kuhn, Inc.; Violet Implement Sales, Inc.; Wellman Seeds; Wells Fargo Bank; and Williamson Insurance Agency.

The Farm Focus Field Day on September 12 from 12:30 p.m. – 4:00 p.m. is free and open to the public. For more information about the field day visit the Farm Focus website at Or call the Ohio State University Extension, Van Wert County office at 419.238.1214.

Archive Issue Contributors: 

Anne Dorrance, Dennis Mills and Pierce Paul (Plant Pathology), Ron Hammond and Bruce Eisley (Entomology), Mark Loux (Weed Science), Jim Beuerlein (Soybean and Small Grain Production), and Peter Thomison (Corn Production). Extension Educators: Keith Diedrick (Wayne), Howard Seigrist (Licking), Glen Arnold (Putman), Roger Bender (Shelby), Harold Watters (Champaign), Ed Lentz (Seneca), Mark Koenig (Sandusky), Bruce Clevenger (Defiance), Alan Sundermeier (Wood), Dusty Sonnenberg (Henry), Curtis Young (Allen), and Gary Prill/Andy Kleinschmidt (Van Wert).

Crop Observation and Recommendation Network

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