CORN
Crop Observation and Recommendation Network

For February, 1999
C.O.R.N. 99-1

In This Issue:

A) Wheat Condition
B) Hybrids with Improved Resistance To Gray Leaf Spot
C) Fungicides for Control Of Gray Leaf Spot
D) New Herbicides in Corn For 1999
E) Weed Control Guide for Ohio Field Crops and Herbicide Selector Computer Program Available
F) Phosphorus Recommendation for Corn, And Soybeans

A) Wheat Condition - Pat Lipps CORN Questions

So far, the wheat crop is surviving the winter fairly well. The winter wheat planting season progressed well last fall due to relatively early harvest of soybeans across the state and favorable weather for timely planting. Fair weather throughout the fall and into the last weeks of December permitted plants in most fields to develop a minimum of several tillers.

The Ohio Agricultural Statistics Service report indicates the number of wheat acres planted last fall was down by only 12% with 1.05 million acres planted. Low wheat prices and stand establishment problems for corn planted directly into wheat stubble contributed to the reduction in wheat acres for the 1998-1999 season.

The January cold and snowy weather did not have a significant impact on the survival of the wheat crop throughout most of the state at this point. There are fields in northwest Ohio that have had standing water problems from melting snow and ice and frequent rains in mid January. Stand losses have been confined to areas where water was ponded for some period of time. The wheat crop must still survive all possible weather conditions that February can produce. Late February and early March with typical freezing and thawing can cause severe loss of stands, especially on poorly drained soils or soils with high clay content. Wheat producers should not attempt to evaluate wheat stands until warmer weather in March initiate spring green-up.

B) Hybrids with Improved Resistance To Gray Leaf Spot - Pat Lipps CORN Questions

Gray leaf spot continues to be one of the most devastating diseases of corn in the state. Although yield losses were not as great during 1998 as in previous years, the disease did cause economic damage in many fields in the east central and south central regions of Ohio.

The fungus causing gray leaf spot survives from one year to the next on corn residues left on the soil surface. This is the principal reason this disease is so important in reduced tillage corn fields. If growers were willing to rotate corn with soybeans and wheat in a three-year rotation and use some form of tillage to help destroy residues over this time period, it would be possible to reduce the importance of this disease in the state. However, crop rotations are more controlled by short-term economics of specific crops than by long term management for productivity.

In addition to rotation, one of the best methods to reduce yield losses to gray leaf spot is to plant a hybrid with improved resistance to the disease. Disease resistance to gray leaf spot is partial, meaning that no high level of resistance exists, but some hybrids have less disease than more susceptible types. Hybrids with partial resistance develop some disease, but the disease develops slower on these hybrids and the plants remain greener longer and are able to produce a better yield. Over the past few years, seed corn companies have been working hard to develop hybrids with improved levels of partial resistance to gray leaf spot.

During 1998, a field study was planted near Apple Creek, OH to evaluate the reaction of some of the hybrids reported to have higher levels of resistance than those tested only a few years ago. Disease levels in this test were moderately high, but most of the disease pressure did not occur until denting growth stage. All seven of the hybrids tested had disease levels significantly lower than the susceptible hybrid Pioneer brand 3394, but the most resistant hybrids had about half the level of leaf tissue damage as this susceptible hybrid. Five of the hybrids had yields significantly higher than the susceptible hybrid. Interestingly, several hybrids produced yields 45 to 69 Bu/A better than the susceptible hybrid. It is important to note that here are hybrids available with moderate levels of resistance to gray leaf spot and with good yield potential. Growers no longer need to sacrifice yield for gray leaf spot resistance. Contact your seed dealer to determine which hybrids are available with improved resistance to gray leaf spot.

Response of selected hybrids with partial resistance to gray leaf spot, 1998

C)  Fungicides for Control Of Gray Leaf Spot - Pat Lipps  CORN Questions

Fungicides have not been widely used to control gray leaf spot in field corn due to the relative expense of the fungicides and difficulty of applying sprays to a field of corn late in the season. Tilt fungicide is labeled for control of gray leaf spot. A three year study near Wooster, using high clearance spray equipment has indicated that consistent yield improvements can be made by applying Tilt (4.0 oz/A, 23 gpa) with drop nozzles at tassel initiation when leaf spots occur on the lowest leaves of the plants. This fungicide application provides limited protection to the leaves above the ear and retards further development of the disease until later in the season. The best response to fungicide application will be on hybrids susceptible to gray leaf spot planted in fields with a persistent disease problem.

Yield (bu/A) response of Pioneer brand 3394 to fungicide application over three years.

D) New Herbicides in Corn For 1999 - Jeff Stachler  CORN Questions

Several products have been labeled since last growing season. The following is a brief summary of those products: Dual II Magnum, Bicep II Magnum (Novartis) - The Dual is a refined product containing more of the active ingredient in the product. Therefore the use rate will be approximately 33% less compared to the old Dual II. Weed control and all other parameters will be the same as before.

Axiom (Bayer) - Axiom is a premix of flufenacet, similar in chemistry to Dual, Harness, Surpass, and Frontier, plus metribuzin (Sencor). Axiom can be applied preplant incorporated (PPI), early preplant (EPP), or preemergence (PRE). The rate range is 13 to 23 ounces per acre. Axiom requires as much rain for activation and has the same longevity in the soil as compared to Dual. Axiom will control annual grasses, lambsquarters and pigweed and provide suppression of waterhemp, eastern black nightshade, and yellow nutsedge and early season suppression of common ragweed. Based on 5 years of OSU research Axiom has controlled annual grasses 15% greater than all other PRE grass herbicides in corn when applied EPP in high grass pressure plots.

Balance (RPAgro) - The active ingredient in Balance is isoxaflutole, which kills plants similarly to Command. Balance can be applied PPI, EPP, or PRE. Balance should be applied only up to 14 days before planting. The rate range is 1-3 ounces per acre. Balance will control velvetleaf, pigweed, waterhemp, burcucumber, eastern black nightshade, smartweed, lambsquarters, and common ragweed and provide early season grass control. Balance is poor on giant ragweed, common cocklebur, morningglory and yellow nutsedge. Based on OSU research, a reduced rate of Balance applied to Liberty Link, Roundup Ready and IMI corn and followed with Liberty, Roundup Ultra, and Lightning, respectively can provide excellent control of weeds in most fields. Balance can injure corn on coarse-textured soils and has been restricted from being applied to certain soil types which is listed in the label. Planting corn at least 1.5 inches deep will greatly reduce the risk of corn injury. Be extremely cautious in using Balance on corn inbreds and speciality corn.

Aim (FMC) - The active ingredient of Aim is carfentrazone, which is similar in chemistry to Authority and is a cell membrane disruptor. Aim is applied postemergence (POST) to corn up to 8 collar stage at a rate of 0.33 ounces per acre. Aim will control eastern black nightshade, velvetleaf, redroot pigweed, morningglory, and lambsquarters if they are less than 3 inches tall. Beyond 3 inches Aim will help in the control of these weeds when tank-mixed with other products. Aim will control velvetleaf up to 36 inches tall. The only adjuvant which should be mixed with Aim is nonionic surfactant at 0.25% volume to volume. The use of any other adjuvant or EC formulated pesticide will cause severe corn injury. OSU research indicates Aim has the same or slightly greater injury potential compared to Resource.

Liberty ATZ (AgrEvo) - Liberty ATZ is a premix of Liberty and atrazine. Liberty ATZ is applied POST to Liberty Link corn up to 12 inches tall. Liberty ATZ will control all annual grass and broadleaf weeds which are less than 4 inches tall, except triazine resistant lambsquarters. Add AMS at 3.0 pounds per acre. Do not apply product from dusk until dawn as poor weed control can be expected.

Northstar (Novartis) - Northstar is a premix of Beacon plus Banvel. Northstar is applied POST over the top of corn from 4 to 20 inches tall or to 6 collars. Northstar will control most annual broadleaf weeds, shattercane, and seedling johnsongrass and suppress many perennial broadleaf weeds and rhizome johnsongrass. Add nonionic surfactant or crop oil concentrate up to 12 inch corn. After 12 inch corn only add nonionic surfactant. Ammonium sulfate or 28% nitrogen may be added to the mixture.

Celebrity (BASF) - Celebrity is a co-pack of Accent plus Banvel. Celebrity is applied POST over the top of corn up to 20 inches tall or to 6 collars. Celebrity will control most annual broadleaf and grass weeds, quackgrass, and rhizome johnsongrass. Add nonionic surfactant and 28% nitrogen or AMS to the mixture.

Other product names - Leadoff is just Guardsman from DuPont, Sterling and Sterling Plus are Banvel and Marksman, respectively, which is sold by Terra.

E) Weed Control Guide for Ohio Field Crops and Herbicide Selector Computer Program Available - Jeff Stachler CORN Questions

The Weed Control Guide for Ohio Field Crops, Bulletin Number 789, is on the Internet and available at your local County Extension office. The Ohio Herbicide Selector Computer Program is also available on the Internet and at your local County Extension office.

F) Phosphorus Recommendation for Corn and Soybeans - Greg LaBarge CORN Questions

With the prospects for low corn and bean prices in 1999 farmers will look for ways to lower their input cost. For farmers with phosphorous soil test levels above 15 PPM (parts per million) or 30 pound per acre there is an opportunity to efficiently produce a crop with crop removal rates of phosphorous fertilization. A 150 bushel corn crop will remove approximately 55 pounds of P2O5 per acre in the grain. Soybeans at 50 bushels will remove 40 pounds of P2O5 per acre.

Soil test levels above 40 PPM or 80 pounds per acre are above the crop response range for phosphorous and do not require any phosphorous broadcast treatment to produce excellent yields. Soil test levels in these ranges can be drawn down by not applying fertilizer without affecting yield.

If P soil test levels are at 15 to 30 PPM the following equation can be used to determine crop removal rates of P to be applied to Corn. Fertilizer Rate=Yield Goal X 0.35. For example a yield goal of 125 bushel per acre would have a crop removal rate of 44 pound P2O5 per acre (125 X 0.35). Crop removal rates for Soybeans to use in the equation are 0.83 per bushel of beans.

Where soil test levels are between 30 and 40 PPM lower rates of fertilization can be applied at lower rates depending upon yield goals. For corn and soybeans the following recommendations can be followed. Yield Goals are followed by recommendations. Corn- 100 bushel/20 pound of P2O5, 120/20, 140/25, 160/30 and 180/35. Soybeans- 30 bushels/10 pounds of P2O5, 40/15, 50/25, 60/25, and 70/30.

More details on fertilization of Corn and Soybeans can be found in the Tri-State Fertilizer Recommendation Bulletin E-2567. This publication puts together over 40 years of field calibration and correlation studies to develop these recommendation. The bulletin is available through your County Extension Office.

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 (Plant Pathology) and Jeff Stachler (Weed Science) EXTENSION AGENTS: Larry Lotz (Fayette), Bruce Clevenger (Defiance), Greg LaBarge (Fulton), Steve Prochaska (Crawford), Ray Wells (Ross) and Barry Ward (Marion).

Editor: Greg LaBarge        Web Editor: Nathan Watermeier

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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