CORN
Crop Observation and Recommendation Network

Mid December, 2000
C.O.R.N. 2000-39

In This Issue:

A) Selecting A Best Soybean Variety For 2001
B) Selecting Corn Hybrids For 2001
C) Double Nozzle Technology Field Studies
D) 2000 Ohio Forage Performance Trials Available
E) CCA Credits For Forage Short Courses

A) Selecting A Best Soybean Variety For 2001 - Anne Dorrance, Dennis Mills, and Jim Beuerlein CORN Questions

Throughout Ohio the largest deterrent to good soybean yields is disease. Diseases such as Phytophthora root and stem rot, Pythium-damping off, Rhizoctonia damping off, Brown stem rot, Sclerotinia White Mold, Phomopsis seed rot and soybean cyst nematode are present throughout most of the state and may reduce yields by up to 30 percent in some locations.

Disease levels and subsequent yield losses are dependent on inoculum levels, the environmental conditions that occur at the time of infection and the susceptibility of the soybean variety. While seed treatment fungicides and cultural practices are powerful tools for disease management, the selection of resistant varieties is the ultimate weapon. Unfortunately, no variety has resistance to all the diseases that may be present in a field.

So a good disease management program includes all three components that work together to manage disease. A good disease management program in combination with varieties with high levels of resistance will provide a high level of disease control in years and/or fields that have moderate to low disease pressure. When conditions are ideal for disease development with the same resistant variety, there will be a low level of infection, and minimal yield loss regardless of the quality of the disease management program.

Selecting the best disease resistant variety using the OSU Soybean Performance Trial Bulletin:

1. Determine what the most serious diseases are for a field. The disease problems encountered during the past five years are likely to be the ones that will cause the largest yield loss and the ones to control next year.
   
   
2. Choose a soybean variety with the highest levels of resistance for the diseases that have been identified as problems in that field. Variety susceptibility to Phytophthora and Sclerotinia can be found in the OSU Soybean Performance Trial Bulletin. Reactions to other diseases are available from seed companies.
   
   a) Phytophthora - There are two types of resistance to Phytophthora, specific resistance (Rps genes) and partial resistance. This past year, in the performance trial, soybean varieties with specific resistance had Rps 1a, 1b, 1c, 1k, 3a and some 2 gene combinations. Partial resistance is effective against all races of Phytophthora, but some disease does develop. Partial resistance scores of 3 to 4 indicate high levels of partial resistance. Scores of 5.5 or greater indicate low levels of resistance. For fields with a history of Phytophthora, choose varieties with both an Rps gene (1k and 3a are better than 1a or 1b) and partial resistance. For more information on how to manage Phytophthora root rot see the OSU fact sheet at: http://ohioline.ag.ohio-state.edu/ac-fact/0017.html
   
   b) Sclerotinia stem rot. Resistance to Sclerotinia is due to another type of partial resistance. There are no varieties with a high level of resistance that will eliminate Sclerotinia as a threat. The better varieties are moderately resistant and will develop less disease than a variety with no resistance under the same inoculum and environmental conditions. Varieties with moderate resistance are indicated with an "M" in the performance trials. For more information on managing Sclerotinia stem rot see the North Central Soybean Research Project Sclerotinia web site at: http://www.plantpath.wisc.edu/NCSRPWhiteMold/ and Ohio's Fact Sheet: http://ohioline.ag.ohio-state.edu/ac-fact/0045.html
   
   
3. Now select varieties that have several different Relative Maturities so all your acreage can be harvested at grain moistures of 13 to 19 percent that produce the highest test weights and the best seed quality. Harvesting during the first dry-down of the grain is an excellent way to dodge serious seed infection by Phomopsis which reduces grain quality.
   
   
4. If your crop lodged in 2000, select a variety that stands well (lodging score 1 or 2). Reducing the seeding rate will also reduce lodging and seed cost.
   
   
5. Lastly, select a variety based on yield from these tests. Selecting varieties that had yields greater than the average for its maturity group will get you into the top 25% of the best yielding varieities, since only about half of the commercial varieties are entered in the trials for evaluation. Most varieties have yield potentials greater than 100 bu/ac and reported yields reflect the performance in the test environment (OHIO) and not their true yield potential. Varieties not in the trials may be poorer yielding than average or have lower levels of disease resistance and should be considered risky choices.

The Ohio Soybean Performance Trials can be found on the web at: http://www.oardc.ohio-state.edu/soy2000/

B) Selecting Corn Hybrids For 2001 - Peter Thomison CORN Questions

Selecting a group of hybrids for planting is a key first step to successful corn production. To stay competitive, you should introduce some new hybrids to your acreage on a regular basis. Genetic improvements during the past 40 years have contributed to steady increases in grain yield potential ranging from 0.7 to 2.6% per year.

Key factors to consider in hybrid selection are maturity, yield potential and stability, stalk quality, and disease resistance. Corn acreage, soil type, tillage practices, desired harvest moisture, and pest problems will determine the relative importance of such traits as dry down, disease resistance, early plant vigor, etc. Certain weed and insect problems may warrant the use of herbicide resistant and Bt corn hybrids. End uses of corn should also be considered. Will the corn be used for grain or silage? Will it be sold directly to the elevator as shelled grain or used on the farm? Are there premiums available at nearby elevators or end users for IP specialty corns such a white food grade or non-GMO corn? What is your capacity to harvest, dry, and store grain?

MATURITY: Choose hybrids with maturity ranges appropriate for your geographic area or circumstances. Corn for grain should reach physiological maturity or "black layer" (maximum kernel dry weight) one to two weeks before the first killing frost in the fall. Using relative maturity (or days?to?maturity), growing?degree?day (GDD) ratings, along with grain moisture data from performance trials will help ensure selection of hybrids differing in maturity and grain dry-down.

Although yields of full?season hybrids usually exceed those of short?season hybrids, early? to mid?maturing hybrids have been developed in recent years with yield potential approaching those of full?season types. In some parts of Ohio, late? to full?season hybrids do not always mature or dry down adequately before frost, which results in wet grain.

Because fossil fuel prices have risen significantly, you should give careful attention to moisture differences between hybrids when evaluating grain yield. Grain drying represents a major portion of the energy requirement for corn production. At a drying cost of $0.04/point/bushel and a corn price of $2.50/bushel, every 1% moisture difference between two hybrids yielding 125 bu/A is worth 2 bushels.

YIELD POTENTIAL AND STABILITY: Plant hybrids that have produced consistently high yields across a number of locations and/or years. The 2000 Ohio Corn Performance Tests indicate that hybrids of similar maturity can vary in yield by over 50 bu/A. Choosing a hybrid because it possesses a particular cosmetic trait, such as "flex" or "girthy" ears, prolificacy, or upright leaves, does not ensure high yields; instead, look for stability in performance across environments.

Review results of state, company, and county performance trials before purchasing hybrids. Because weather conditions are unpredictable, the most reliable way to select superior hybrids is to consider performance during the last year and the previous year over a wide range of locations and climatic conditions. When using University performance trials results, two years of data from several locations is usually adequate. Test summaries for three or more years may exclude new hybrids with improved performance potential. Moreover, there is considerable turnover in the hybrids evaluated in state performance tests - with as many as 50% or more of the hybrid entries changing from one year to the next.

Results for the 2000 Ohio Corn Performance Trial are available online at http://www.oardc.ohio-state.edu/corn2000. Since assessment of a hybrid performance is enhanced by using a number of test sites, farmers along Ohio's border with neighboring states should consider checking results of the Purdue, Kentucky, Michigan State, Pennsylvania, and West Virginia Corn Test results. An online version of the 2000 Indiana corn test results (Performance of Commercial Dent Corn Hybrids in Indiana, 1998?2000) is available at http://www.agry.purdue.edu/ext/variety.htm. Growers interested in results of the corn hybrid silage trails should consult the Michigan State University and Pennsylvania corn hybrid tests which include silage yields. The North Central Crop Evaluation Committee web site http://www.ksu.edu/kscpt/nccec/ provides links to corn hybrid test results from state universities across the Corn Belt.

STALK QUALITY AND LODGING: Avoid hybrids with poor stalk quality even if they show outstanding yield potential. Stalk quality is particularly important in areas where stalk rots are perennial problems, or where field drying is anticipated. If you have your own drying facilities and are prepared to harvest at relatively high moisture levels (less than 25 percent) or are producing corn for silage, then standability and fast drydown rates may be less critical selection criteria.

Traits associated with improved hybrid standability include resistance to stalk rot and leaf blights, genetic stalk strength (a thick stalk rind), short plant height and ear placement, and high "staygreen" potential. Staygreen refers to a hybrid's potential to stay healthy late into the growing season, after reaching maturity, and should not be confused with late maturity. European corn borer (ECB) resistance in Bt hybrids minimizes ECB stalk injury that can promote stalk rot in corn. However, the Bt trait is not a substitute for good stalk quality and tolerance to stalk rots. In 2000, stalk lodging was a major problem in parts of the western Corn Belt, as well as in localized areas of Ohio. The severity of this problem was probably due to a combination of interacting factors involving weather stress, disease, and genetics, and serves to remind us of the need to diversify hybrids and select high yielding hybrids which have exhibited good standability across a range of environmental conditions.

DISEASE RESISTANCE AND TOLERANCE: Table 1 lists the most common disease problems of corn in Ohio. In 2000, Anthracnose and Gibberella stalk rots caused serious lodging in localized areas. Although gray leaf spot (GLS) was not a major problem in 2000, GLS resistance should be a major consideration in no-till cropping systems, especially if you plant continuous no-till corn. In recent years, several corn diseases have become more prevalent in Ohio including Stewart's bacterial leaf blight and Diplodia ear rot. In 2000, common rust was probably the most widely observed corn disease. However rust is generally not a major problem in Ohio. According to Dr. Pat Lipps, OSU plant pathologist, grain losses to common rust in Ohio are usually limited, but rust damage to leaves predisposes corn to stalk rots and lodging. Corn growers should obtain information from their seed dealer on hybrid reactions to specific diseases that have caused problems or that have occurred locally.

C) Double Nozzle Technology Field Studies - John Cardina CORN Questions

There has been a lot of press lately about the "double nozzle" sprayer developed by scientists at the Laboratory for Pesticide Application Technology (LPCAT)at OARDC in Wooster. During the 2000 growing season OSU weed scientists conducted three field experiments with side-by-side comparisons of conventional and double nozzles at several rates of application of Roundup Ultra.

The experiments represent three situations where this herbicide is commonly used: springtime burndown of wheat cover crop with winter annual weeds, postemergence control of grass and broadleaf weeds in Roundup Ready soybeans, and control of annual and perennial weeds following wheat harvest.

In the first two experiments, we used rates of 1, 0.5, 0.25, and 0.125 quarts of Roundup per acre in both sprayers. In the burndown study the standard sprayer used 8002 flat-fan nozzles at 10 gal per acre (GPA). In the postemergence study the standard sprayer used 8003 nozzles at 10 GPA.

Three experienced raters evaluated weed suppression approximately 1, 2, and 3 weeks after application. Two of the raters were not familiar with the plot plan or the experimental treatments. Weed biomass was determined by harvesting weeds in two 1-m-squared areas per plot. Analysis of variance indicated no significant difference between nozzles in percent weed control or biomass for all evaluation dates of both experiments. There were occasionally significant interactions between herbicide rate and nozzle type, but these appeared not to be biologically meaningful.

In the third experiment (wheat stubble), the double nozzle malfunctioned and weed control was poor for all herbicide rates. Two points that might be of interest: the double nozzle sprayer was calibrated by one of its developers for these experiments; and neither the nozzle manufacturers nor Monsanto provided financial support for this study.

At this point we suggest that these results are not conclusive. Additional field studies will be needed to determine if these results are real or aberrations. However, these results raise the question of how to evaluate the double nozzle in comparison with conventional nozzles.

There are many environmental, mechanical, and formulation variables that influence the level of weed control achieved as herbicide rates are lowered. It is often possible to achieve good to excellent weed control with half-rates and sometimes less using conventional sprayers. Many nozzle designs and adjuvants have been tested in an effort to achieve good weed control at reduced rates on a consistent basis. Even with optimum droplet size and formulation chemistry, environmental conditions can limit efficacy.

It is not clear at this point whether the double nozzle will result in consistently better weed control at reduced rates than would be achieved with a conventional sprayer. These limited side-by-side comparisons under field conditions suggest that conventional flat-fan nozzles and the double nozzle design are equally effective at equivalent rates of glyphosate.

D) 2000 Ohio Forage Performance Trials Available CORN Questions

The 2000 Ohio Forage Performance Trials Report is now available at county extension offices and on-line at http://www.ag.ohio-state.edu/~perf/, and is also included in a special insert of Ohio's Country Journal this month. The report summarizes performance results and characteristics of 67 commercial alfalfa varieties, 9 red clover varieties, and 47 cool-season grass varieties planted in 14 trials at six Ohio locations.

E) CCA Credits For Forage Short Courses - Mark Sulc CORN Questions

A total of 11.5 continuing education credits for Certified Crop Advisors (CCA) have been approved for the OSU Forage Production Short Courses to be offered in January. The breakdown of the credits is: 1 for nutrient management, 8.5 for crop management, and 2 for pest management.

The Ohio State University's Forage Production Short Course is an intensive three-day learning experience, planned for two sites in January. Dates, locations and phone numbers to register are:

Jan. 8-10, Defiance OSU Extension office
(419) 782-4771
Jan. 22, 23, and 25, Zanesville
(740) 454-0144.

Each site is limited to 30 participants, and the $50 pre-registration is required. Get registration forms from county Extension offices in Ohio. Registration materials are also posted on the web at: http://www.ag.ohio-state.edu/~forages/education/fpsc00_01.html Or go to: http://www.ag.ohio-state.edu/~forages and click on "Events" to find the Forage Production Short Courses listed and a link to course registration.

The curriculum will cover all aspects of forages --from production to storage to utilization -- but the emphasis will be on management and how to produce high-quality forages more efficiently and more effectively. A team of specialists will provide classroom instruction plus hands-on activities, such as evaluating hay quality, identifying forage species, and computer program demonstrations. Each participant will receive a notebook full of valuable references, bulletins, fact sheets and articles.

If you have specific questions about the course, contact Mark Sulc at (614)292-9084 or sulc.2@osu.edu

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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.

Editor: Greg LaBarge        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.

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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.

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