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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2008-06

Dates Covered: 
March 19, 2008 - April 2, 2008
Harold Watters

Private Pesticide License Renewal by March 31st

Authors: Glen Arnold

As March draws to a close farmers should make certain that they have attended the needed recertification training if their private pesticide applicator license is due to expire on March 31st 2008.

The Ohio Department of Agriculture has a web site at that farmers can access to check the current status of their license. At this site you will need to input your private pesticide applicator license number and your last name, then click on search.

The next web site page that appears will have information on the categories you have on your private pesticide license, hours of recertification credits you may have attained, your recertification status (complete or incomplete), and at the bottom of the page, your categories still needed. It is possible to have your recertification status listed as complete even though you have not recertified in all the categories on your license. If you fail to complete recertification for those categories listed, you will lose them and they will not appear on your new license.

Only a few private pesticide recertification opportunities are available across Ohio. They are listed at the pesticide education web site at

Farmers wanting to get a private pesticide applicators license or add categories to their current license can do so by taking the exam at one of the Ohio Department of Agriculture (ODA) testing locations listed at this web site Be certain to contact the ODA before attending a testing session. Their toll free number is 1.800.282.1955. When you reach the automated phone tree, choose extension three and then extension one. That will get you to the pesticide section of ODA.

Early-spring Weed Control in Wheat

Authors: Mark Loux

Dense populations of winter annual weeds can compete with wheat in early spring and slow the rate of crop development. Herbicides should be applied soon to minimize the impact of these types of weed populations on the wheat. Herbicides will be most effective where it is readily apparent that plants have resumed active growth. Winter annual grasses, such as downy brome, cheat, annual bluegrass, and annual ryegrass, should be controlled as soon as an inch of new growth has occurred. The wheat herbicides available for control of grasses, Axial, Maverick, Osprey, and Olympus, are most effective when applied in the fall, and effective spring activity is dependent upon the weeds being small. Winter annual grasses are not nearly as prevalent as winter annual broadleaf weeds, though, and the major problems in many fields consist of chickweed, purple deadnettle, henbit, marestail, etc. While several herbicides are available for control of winter annuals, Harmony GT or Harmony Extra should be included where control of chickweed is desired, since these are the only herbicides that control this weed.

Herbicides applied in early spring usually eventually control emerged weeds, but activity can be slow under the typically cool conditions in March. Applications this early are not likely to effectively control dandelions, which have not resumed active growth for the most part. Fields treated at this time should be scouted again in April to determine if later-emerging populations of summer annual weeds, Canada thistle, wild garlic, or other weeds require another herbicide treatment. In fields without winter annuals, delay herbicide application until later in spring, and select herbicides based on scouting.

Be sure to follow label guidelines to minimize risk of crop injury and yield loss. Labels for some products specify the number of tillers or leaves that wheat should have before treatment is allowed. All labeled wheat herbicides can be applied prior to jointing, but the number of herbicide options decreases as wheat progresses through jointing and more advanced growth stages. Wheat should be dissected to determine growth stage, because size is not a good indicator of stage. Weather and soil conditions can affect the risk of crop injury from certain herbicides. Injury from ALS inhibitors (Harmony Extra, Express, etc) is more likely when wet soils and cold temperatures are inhibiting wheat growth.

Most herbicides can be applied using 28% UAN as the spray carrier, although some labels do not provide much guidance on this. Results of OSU research indicate that wheat should tolerate application of herbicide in 28% UAN well into April, as long as the restrictions on herbicide labels relative to wheat growth stage are followed. For products that are applied with surfactant, consult labels about the surfactant rate when applying in water vs 28%, since surfactant rates may be reduced to minimize the risk of injury when applying in 28%. Guidelines and effectiveness ratings for wheat herbicides can be found in the 2008 Weed Control Guide for Ohio and Indiana.

Wheat Assessment and Considerations

Authors: Jim Beuerlein, Pierce Paul

It is still too early to make adequate assessments of stand survival or response to fertilizer. Assessments should not be made until after the risk of excessive freezing and thawing, which is usually late March for southern Ohio and first of April for northern Ohio. However, the spring warm-up appears to be a bit late this year. At green-up, the first inspection should be for heaving damage.

No-till planting and early planting greatly reduce heaving damage which is recognized when the crowns of the plants are pushed up out of the soil as the soil freezes and thaws during late winter. Close examination of the plants indicate that the crowns and upper roots are exposed with only a few roots remaining in the soil. These plants will green up and look normal for a while, but within a few weeks heaved plants will turn brown and die. Growers generally describe this as fields 'going backwards'. Heaving is generally worse in fields with compacted, wet, soils. Generally, heaving is more severe in conventional tilled fields with little surface residue than in no-till fields with residue that protects against wide changes in temperature of the upper few inches of the soil. Wheat that is planted too shallow is also more prone to heaving problems than wheat that has been planted at the recommended one and a half inches deep.

At the same time fields are inspected for heaving, plants should also be examined for lower stem and root disease problems. As the soil temperature increases, so does the activity of disease-causing fungi. Disease problems are likely to occur first and be most severe in low-lying areas of the field. Excess soil moisture in these areas keeps soil temperatures cool, increases relative humidity, and exposes young plants to pathogen infection. Some soil-borne pathogens thrive under conditions of relatively cool temperatures, high relative humidity, and wet soils. Disease problems can be identified by examining the roots for lesions and discolorations. Dig plants from the field, wash off all soil and examine the crowns. Peal the leaf sheaths down to expose the inner parts of the crown. The tissues in healthy plants should be a creamy white color. If the internal tissues are brown or discolored, then these plants are likely dead or will soon be dead. Pathogen infection leads to root rots and seedling blights, leaving plants stunted with poorly developed roots and tillers.

Adequate tiller number and proper development are essential for high yields. Yield potential is reduced if tiller numbers fall below 25 per square foot after green up. Fifteen tillers per square foot is considered minimum for an economic crop. The number of tillers per square foot is equal to the number of tillers in 19.2 inches of 7 inch wide rows or 14.5 inches of 10 inch wide rows. Obviously, late planted fields should be visited to determine if adequate numbers of tillers are present, but excessive tillering is unnecessary and may lead to lodging. Fields planted within 10 to 14 days of the Hessian Fly Safe Date using 1.3 to 1.6 million seed per acre (18 to 24 seed per foot of row) with about 20 to 25 lb of actual nitrogen/A applied at planting rarely have problems with low tiller numbers in the spring. In fact they generally have many more tillers than are needed for maximum yield. Our experience from counting heads of wheat in fields prior to harvest indicate that most Ohio fields have from 40 to 60 heads per foot of row. If 20 seed were planted per foot of row then each plant will end up with 2 to 3 head bearing tillers. These are the main tillers that developed during fall growth.

Spring N should be applied now or anytime before early stem elongation (Feekes GS 6). Applications should be made when field conditions are appropriate for equipment traffic. Research data shows timing is not critical for yield as long as N is applied by Feekes growth stage 6, which often occurs in early to mid-May.

Transgenic Corn and the 20 Percent Refuge

Authors: Ron Hammond, Andy Michel, Bruce Eisley

As we prepare for the coming planting season, we need to remind growers about Insect Resistant Management (IRM) requirements which necessitate the use of a refuge when planting Bt transgenic corn, whether for rootworm larval control or European corn borer, or when planting a stacked trait including the Bt genes for both pests. The major requirement is that growers MUST plant a 20% refuge area to non-Bt corn. A refuge is simply a block or strip of corn planted with a hybrid that does not have the Bt gene for controlling the target insects. The purpose of this refuge is to maintain a pest population that is not exposed to the Bt toxin, allowing susceptible insects to remain alive in the population to mate with any resistant insects that survive in the transgenic area. There are three families of transgenic corn that growers can plant, YieldGard, Herculex, and Agrisure. All three of these have Bt hybrids for corn borer and corn rootworms separately, and stacked hybrids containing the traits together.

Growers should be aware of a major difference between the refuge requirement for each insect, that being the distance of the refuge from the Bt corn. For corn borer, the non-Bt refuge can be within, adjacent, or near the Bt field, but has to be within 1/2 mile, preferably within 1/4 mile. For corn rootworm, the non-Bt refuge has to be within the same field as the Bt corn, or adjacent to it. When adjacent, it can be separated at most by a ditch or a road, but not by another field. If growers are planting a stacked hybrid containing both types of Bt, they have two options on how to manage their refuge. The first choice is planting separate refuges for each target pest. However, we recommend the second choice, the common refuge approach where corn without any Bt technology is planted. The common refuge, also 20%, must be within or adjacent to the transgenic field, as is the case with Bt-rootworm transgenic corn.

When planting the refuge whether for a single trait or stacked traits, there are various planting options, including a separate field refuge (mainly for corn borer), an adjacent field, a separate but adjacent block next to the Bt, a block refuge within the Bt field, the refuge planted along the perimeter, or a split-planter refuge. If planting the refuge using a split planter, the strip width must be at least 4 rows for corn borer (6 preferred) and corn rootworm. There are other guidelines related to IRM and refuges, including management of the Bt field and non-Bt refuge, and use of other insecticides. Growers should see their seed dealer for these guidelines. Also available on the National Corn Growers website:

We would point out that these are government regulations that must be followed. Growers who fail to follow IRM requirements risk losing access to Bt corn technology.

Why I Inoculate Soybeans

Authors: Jim Beuerlein

The soybean is a legume who’s seeds generally contains 37% to 45% protein by weight. Depending on the protein content, a bushel of soybeans will contain between three and four pounds of nitrogen. The production of a 60-bushel per acre crop requires in excess of 300 pounds of nitrogen. Some of the nitrogen comes from the oxidation of soil organic matter with the balance produced by bacteria residing in nodules on the plant’s roots.

In recent years, inoculant manufacturers have focused their research and development efforts on finding ways to improve inoculants. One focus is improving strain selection and increasing the number of viable bacteria per gram of product. Combining strains of Bradyrhizobium japonicum that are most productive in different environments results in products that are productive over a wider range of environments. Other areas of focus have been on easing application through the development of liquids and improved dry products. Combining organisms that offer plant growth promotion hormones or disease control in conjunction with regular rhizobials is another new development. Other areas of interest are the biological signals that induce nodulation. Combining the signal compounds with inoculants also allows companies to speed up the inoculation process. The addition of “extenders” to inoculation materials allows the materials to be applied to seed up to 90 days or more before planting without loss of productivity if the seed is stored properly. The extender materials also extend the longevity of bacteria cells applied to seed that has been treated with fungicides and in some cases allows the combined application of fungicides and inoculation materials. High quality inoculants contain over 2 billion live bacteria per gram, and use at the recommended rate results in 800,000 to 1,400,000 bacterial cells per seed depending on seed size and quality of the inoculant material.

Caring for inoculation products
Rhizobia cells survive best at temperatures of 40 - 80 degrees F. Prior to application, inoculants should be stored in a cool place and out of direct sunlight. Packets exposed to sunlight during the planting season will overheat rapidly due to the greenhouse effect and all the bacteria can be killed in less than an hour of exposure. When transporting the inoculant to the field, try to keep it cool.

Applying inoculation materials
Before applying an inoculant, it is important to check for compatibility with chemical seed treatments, fungicides and insecticides. Chemical compatibility varies for different products, but you can check the compatibility at company websites listed below. Better still, ask your seed supplier to inoculate the seed for you since s/he has already checked the compatibility of the pesticides and inoculants s/he uses.,,,,,,

Crop Production Basics Still Deliver the Most Profit

Authors: Jim Beuerlein, Peter Thomison, Mark Sulc, Robert Mullen

More new technology has become available to producers in the last five to ten years than in the 25 preceding years. There are transgenic corn hybrids with Bt insect resistance and herbicide tolerance, low linolenic soybeans, seed applied fungicides, foliar fungicides, plant growth regulators, new seed inoculants, no-till, reduced herbicide rates, enhanced G.P.S./G.I.S. systems, yield monitors, new planters, tracks on machinery, plastic parts and new threshing mechanisms for combines, new power units and transmissions, air seeders, and on and on. For each of these new technologies, we spend a lot of time trying to understand how they work and if they will help us be more profitable. With all this excitement, it is easy to forget the basic principles that are the foundation of profitable crop production. University agronomists and county ag professionals, along with many crop consultants and professionals, have all noted that many producers are spending less time choosing varieties and hybrids, less time scouting and walking fields, not testing the soil as often as needed, failing to rotate crops, not paying attention to crop disease control, not harvesting in a timely manner, and overlooking other basics that are sure profit generators. Some growers believe that new technologies can replace proven cultural practices (e.g. substituting stacked trait hybrids and foliar fungicides for crop rotation). Many of us are not applying enough management to our crop production programs and lower yields are a result. Following is an abbreviated checklist of appropriate input for several crops.

SOYBEAN (Disease is the worst problem)
1) Select varieties tolerant to the diseases you have experienced in the past.
2) Rotate crops, 3 to 4 year rotations will keep most disease under control.
3) Plant as early as soil conditions allow between April 15 and May 20.
4) Row spacing should be 15" or less.
5) Plant using a skip-row system to allow post emergence applications.
6) Seeding rate should be 125,000 to 200,000 seeds per acre.
7) Plant 0.75" to 1.5" deep and into moist soil.
8) Use fungicide treated seed.
9) Inoculate the seed as you fill the planter or drill.
10) Soil P should be 15 to 30 ppm
11) Soil K should be 85 to 215 ppm depending on CEC value.
12) Soil pH should be 6.5 to 7.0
13) Control weeds without stressing the crop (use low rates when possible).
14) Post emergence systems allow precise materials and rates to be used.
15) Control insects if they reach threshold numbers.
16) Plant a whole range of maturities to spread out harvest so all grain is harvested on the first dry-down between 13% and 19% moisture for maximum test weight and minimum FM.

1. Choose high yielding adapted hybrids. Pick hybrids that have produced consistently high yields across a number of locations or years. Select high yielding Bt rootworm resistant hybrids when planting after corn or where the western corn rootworm soybean variant is present. Select hybrids with high ratings for foliar and stalk rot diseases when planting no-till or with reduced tillage, especially after corn.
2. Plant hybrids of different maturities to reduce damage from diseases and environmental stress, and spread out harvest time and workload.
3. Aim to complete planting by May 10. If soil conditions are dry, begin planting before the optimum date but avoid early planting or poorly drained soils. If planting late, after May 25, plant corn borer Bt hybrids
4. Plant full season hybrids first, then alternately plant mid- and early-season hybrids.
5. Adjust seeding depth according to soil conditions. Plant 1 1/2 to 2 inches deep. Monitor periodically during planting operation and adjust for varying soil conditions.
6. Adjust seeding rates on a field by field basis. On productive soils, which average 175 bu/A or more, final stands of 30 - 32,000 plants/acre may be required to maximize yields.
7. Make sure the planter is in good working order. Inspect and adjust every part of your planter to improve stand establishment. Slow down (4 1/2 to 5 mph) to optimize plant spacing within row. Uneven emergence affects crop performance because of competition from larger, early emerging plants.
8. Supply the most economical rate of nitrogen. This is critical with today’s increased N costs. Supply N in such a fashion to minimize loss potential (incorporation/injection, consider stabilizers under high risk applications, etc.).
9. Avoid unnecessary phosphorous and potassium application. Utilize soil testing to guide decisions. High soil tests do not require additional inputs.
10. Use seed firmers to improve seed-soil contact
11. Perform tillage operations only when necessary and under proper soil conditions. Deep tillage should only be preformed when a compacted zone is detected and soil conditions are dry (usually late summer).
12. Take advantage of crop rotation - corn grown after soybeans will typically yield 10-15% more than corn grown after corn.
13. Determine harvest dates by crop maturity, not the calendar. Harvest loss increases 1-2% for each week of harvest delay. The ideal grain moisture for harvest is 25%.

WHEAT: (Disease is the biggest problem)
1) Select varieties with disease tolerance and resistance and use fungicide treated seed.
2) Plant within 10 days after the Fly-Safe-Date (FSD) for your county
3) Apply 20 to 40 pounds of N at planting for increased fall growth and earlier heading in the spring.
4) Seed at the rate of 20 to 25 seeds per foot of row when planting within three weeks of the FSD and 30 seeds per foot of row after that time.
5) Seed at a depth of 1 inch.
6) Soil pH should be above 6.0, soil P above 30 ppm, and soil K above 135 ppm.
7) Make spring nitrogen applications between March 1st and April 15th. Follow Tri-State recommendations for nitrogen application rates.
8) Broadleaf weeds should be controlled with spring applications of appropriate rates of 2,4-D or other materials before jointing (usually April 15-May 15).
9) Harvest at a grain moisture of 17 to 20 percent. Test weights are usually highest when harvested at that moisture.

1) Soil test and make applications of lime, P and K at least six months ahead of seeding.
2) Soil pH should be above 6.0 for grasses and clovers, and above 6.5 for alfalfa.
3) Soil P should be at least 15 ppm for grasses and at least 25 ppm for alfalfa and clovers.
4) Soil K should be 90 to 150 ppm, depending on species and CEC value.
5) Control perennial and biennial weeds the year before seeding. Most perennial and biennial weed species are easier to control in autumn.
6) Match forage species to soil and site limitations (species differ in tolerance to poor drainage).
7) Select disease resistant varieties with proven yield performance for your area.
8) Inoculate legumes with correct Rhizobium inoculant. Make sure inoculant is fresh. If seed is pre-inoculated, make sure seed is stored in a cool, dry environment until planted.
9) For conventional seedbeds, prepare a smooth, firm, and weed-free seedbed.
10) For no-till and reduced tillage seedings, control or suppress existing vegetation.
11) Calibrate and adjust seeders before seeding.
12) Do everything possible to ensure good seed coverage with excellent seed to soil contact. Plant no deeper than ¼ to ½-inch. For spring plantings, plant in April as soon as conditions are fit. For late summer seedings, plant as early in August as possible when soil moisture is present.
13) For pure grass seedings, apply 30 lb/acre of nitrogen at seeding time, and 30 to 50 lb/acre of nitrogen in late summer when moisture is available for good growth.
14) Weed control is most critical during the first 60 days of forage seedling growth. Use herbicides as necessary according to label directions.
15) First harvest should occur about 60 to 70 days after emergence, depending on conditions. It is advisable to not graze the very first growth.
16) If a small grain companion crop is used, remove it for silage at boot/early heading stage.
17) Scout for insect pests and take corrective action in a timely manner. New legume seedlings are especially vulnerable to potato leafhopper infestations.
18) Do not harvest a new legume seeding after September 10.

1) Use soil tests and crop removal rates as a guide for maintenance topdress applications of fertilizer. Forages remove 13 lb of P2O5 and 50 lb of K2O per ton of dry matter harvested.
2) Topdress applications after the first harvest or in early fall for best results. Soils are usually dry and workload is less at those times.
3) On stands with less than 25 to 30% legume, split apply nitrogen after each harvest at 40 lb/acre per ton of expected yield for hay or silage.
4) Adequate fertility, weed control, and rotational grazing management can dramatically improve pasture productivity and carrying capacity.
5) Use strategic nitrogen applications to stimulate grass growth in pastures. Applications of 50 to 60 lb N/acre in early summer and again in early August will promote growth when it is needed, rather than applying a large amount in early spring when grass growth is usually excessive in pastures.
6) For hay fields, make a timely first harvest to achieve high quality forage on the largest cutting of the year.
7) Allow legume stands to flower once during late summer to improve persistence. Cutting at more advanced stages of maturity in late summer has a much smaller penalty on forage nutritive value than cutting at advanced stages of maturity in the spring and early summer.
8) Fall cutting can be detrimental to stand persistence and often reduces next year’s yield. Late fall cutting can increase the risk of crown heaving on heavier textured soils.
9) Scout for insect pests. Take corrective action in a timely manner as needed. Forage legume yields are especially reduced by potato leafhopper during the summer months. Potato leafhopper resistant alfalfa varieties are an excellent tool in areas where this pest often reaches damaging levels.
10) Take steps to minimize compaction damage to forage plants. Avoid traffic on forage stands when soils are excessively wet.
11) Store hay under cover and off the ground to reduce spoilage losses.

For more information, consult the following:

The Ohio Agronomy Guide (Bulletin 472)
Online at

2008 Weed Control Guide (Bulletin 789)
Online at

Tri State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa
Online at

The Ohio Crop Performance Trials
Online at

and numerous fact sheets available through all Ohio State University Extension county offices, or on the web at

Archive Issue Contributors: 

Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), Jim Beuerlein (Soybean & Small Grain Production), Peter Thomison (Corn Production), Mark Sulc (Forage Production), Robert Mullen (Soil Fertility) and Mark Loux and Jeff Stachler (Weed Science). Extension Agents: Todd Mangen (Mercer), Roger Bender (Shelby), Howard Siecrist (Licking), Glen Arnold (Putnam), Greg LaBarge (Fulton), Steve Foster (Darke), Harold Watters (Champaign), Mike Gastier (Huron), Mark Koenig (Sandusky), Wes Haun (Logan) and Marissa Mullett (Coshocton).

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.