http://www.ag.ohio-state.edu/~corn/

CORN
Crop Observation and Recommendation Network

June 25 to July 1, 2001
C.O.R.N. 2001-19

In This Issue:

A) Considerations for Wheat Harvest
B) Ear Yield Components in Corn Determined During Late Vegetative Growth
C) Large Weeds in Soybeans
D) Resistant Marestail Request
E) OSU Weed Science Field Day

A) Considerations for Wheat Harvest (Pat Lipps) CORN Questions

Wheat is advancing rapidly through its last stages of ripening. Fields are ready for harvest in southern Ohio and only a week or two away in northern Ohio. Disease levels have not advanced to any great extent over the last week and any additional disease will have little or no affect on yield at this point anyway. The crop is made! Now lets make sure it gets in the bin in good shape.

Wheat growers should make it a point to deliver the best quality grain they can to the wheat processors. Ohio is known for its high quality wheat and Ohio wheat growers should strive to maintain this reputation. It is to our advantage to have wheat millers seek Ohio grown grain on the market. Many things can happen to a wheat crop before and during harvest that can affect overall quality of the grain. It takes only a little bit more effort to do a good job of producing quality grain. Fortunately, diseases have not been a big problems this year. That was a surprise with all the rain that crossed the state over the past month. Most counties have reported only low level of head scab, but a few locations have fields with up to 10% or more heads affected. Growers should pay particular attention to harvesting fields with head scab. Get them harvested as soon as possible.

Growers should attempt to avoid weathering of ripe grain by harvesting as soon as the fields are ready. Weathering by wetting and drying causes the kernels to swell and shrink which seriously affects test weight and flower yield during milling. Increase the air flow in the combine to eliminate any small, shriveled kernels. Scab affected kernels are shriveled and light weight. Attempt to eliminate these kernels by blowing these out the back of the combine. This will effectively increase test weight and reduce the overall mycotoxin level that is associated with scab affected kernels. As soon as grain is harvested, dry it to 14% moisture for storage. Any molds that may be present on the grain will not grow at this low moisture level. Maintaining stored wheat near 14% moisture will prevent accumulation of mycotoxins and help preserve grain in good condition. Check grain in storage bins frequently for hot spots and wet areas. Take care of any problems early, before they become big problems.

B) Ear Yield Components in Corn Determined During Late Vegetative Growth (Peter Thomison) CORN Questions

During the rapid phase of corn vegetative growth - currently evident across most of Ohio - ear yield components are being determined. Kernel row numbers per ear are generally established by V12 (the 12-collar stage). Kernel row number is generally less affected by environmental conditions than by genetic background. Corn hybrids characterized by "girthy" ears exhibit more kernel rows (e.g. 18 or 20 rows) than hybrids with long tapering ears (e.g. 14 or 16 rows). Determination of kernels per row is usually complete about one week before silking (R1) or about the V17 stage, and is associated with ear length. Unlike kernel rows per ear, kernels per row can be strongly influenced by environmental conditions, so severe stress such as a drought occurring the two weeks prior to pollination can reduce kernels per row and ear length. Dr. Bob Nielsen at Purdue University has recently written a comprehensive article on this subject entitled "Ear Initiation & Size Determination in Corn" that includes excellent pictures. This article is available on-line at: http://www.agry.purdue.edu/ext/corn/news/articles.01/Ear_Size-0618.html

C) Large Weeds in Soybeans (Jeff Stachler) CORN Questions

When selecting the proper herbicide application rate, always choose the highest rate for the largest and most difficult to control weed species in the field. Soybean injury may occur due to the use of the highest rate, however it is still early enough in the season for the soybean crop to recover from the injury. If the large weeds are not controlled now, higher yield losses can be expected. When weeds are large, spray coverage becomes more difficult and weed escapes can be expected. Using a higher volume of carrier and higher pressures can improve coverage, but do not use higher pressure on windy days. Choose products that control the most prevalent weed species in the field to reduce competition and do not worry about killing all species as it is usually impossible.

For Roundup Ready soybeans, if weeds are greater than 12 inches, a glyphosate rate of 1.125 pounds of acid equivalent/A (48 oz/A - Roundup Ultra) should be considered. If weeds are greater than 18 inches then consider a glyphosate rate of 1.5 pounds of acid equivalent/A (64 oz/A - Roundup Ultra). The following weed species are hard to kill with glyphosate and high rates should always be considered: marestail, prickly lettuce, velvetleaf, eastern black nightshade, morningglory, Pennsylvania smartweed, common dandelion, curly dock, yellow nutsedge, milkweed, and sometimes common lambsquarters. For some species a tank-mix partner may be a better option. For instance, Raptor or Pursuit may be tank-mixed to help control eastern black nightshade and velvetleaf or FirstRate may be tank-mixed to help control velvetleaf, morningglory, and marestail, or Classic may be tank-mixed to help control common dandelion. FirstRate will not help to control ALS-resistant marestail or other ALS-resistant species.

For STS soybeans consider additional amounts of Classic or Harmony GT for some weeds, especially for common lambsquarters. For large giant ragweeds consider a half or full rate of FirstRate tank-mixed with Synchrony, although ALS-resistant ragweeds will not be controlled. Flexstar at 1.3 pints/A or Cobra at 12.0 fluid ounces/A can be mixed with Synchrony to improve giant ragweed and eastern black nightshade control. Apply MSO (methylated seed oil) and 28 % Nitrogen with the Synchrony when in a tank-mix to improve control.

For non-STS or Roundup Ready soybeans consider Raptor for common lambsquarters control. Use FirstRate for control of large giant and common ragweed and marestail. FirstRate can be applied up to 0.6 ounce/A in a single application for large weeds, but if they are ALS-resistant, higher rates of FirstRate will not increase control.

A Raptor plus Flexstar, Cobra, or Blazer combination is an option for fields with lots of different species, but if grasses are not dead within 7 to 10 days, then consider an application of Select. Flexstar plus FirstRate plus Harmony GT plus a post-grass herbicide is another combination that provides broad-spectrum control. A Basagran plus Flexstar plus Harmony GT plus a post-grass herbicide is another combination that can provide broad-spectrum control. Splitting the application between broadleaf and grass herbicides will provide more consistent grass control, especially when the grasses are large and yellow foxtail or barnyardgrass is present.

D) Resistant Marestail Request (Jeff Stachler) CORN Questions

As postemergence herbicides are applied, be sure to check fields 7 to 10 days after application, to make sure the herbicide has controlled the weeds. If marestail has survived from an in-crop application of Roundup, we would like to know about it. If other weed species are not being controlled by postemergent herbicides, especially ALS or ACC-ase products, please contact Jeff Stachler at 614-292-1393.

E) OSU Weed Science Field Day CORN Questions

Mark your calendar! The OSU Weed Science field day will be held on Wednesday, July 11 at the OARDC Western Branch near South Charleston. This tour of our research plots is free and mostly self-directed. The plots include hundreds of herbicide combinations, recently labeled herbicides like Valor and Callisto, some experimental herbicides, and a preemergence herbicide screen with 27 different crop and weed species. The tour starts at 9 AM and typically ends around noon. Lunch is not provided, but there are restaurants in nearby Springfield. Western Branch is about 5 miles south of I-70 on State Route 41.

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 and Dennis Mills (Plant Pathology), Jeff Stachler (Weed Science), Peter Thomison (Corn Production) and Ed Lentz (NW District Agronomy)
Extension Agents: Dave Jones (Allen), Barry Ward (Champaign), Steve Prochaska (Crawford), Dennis Baker (Darke), Bruce Clevenger (Defiance), Gary Wilson (Hancock), Ray Wells (Ross) and Clark Hutson (Seneca)

Editor: Clark Hutson 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.