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

CORN
Crop Observation and Recommendation Network

For June 21 to 27, 1999
C.O.R.N. 99-14

In This Issue:

A) Dry Weather and Stressed Beans
B) Check Fields for Two-spotted Spider Mites
C) Bean Leaf Beetle Watch
D) First Generation Corn Borer Levels Low
E) ALS Resistant Ragweed
F) Will This Be a Year to Double Crop Soybeans?
G) Hail and Wind Injury to Corn
H) Horticulture & Crop Science Chair Interviews

A) Dry Weather and Stressed Beans - Anne Dorrance CORN Questions

Several samples of soybeans with lesions at the soil line were received this week. The lesions when moistened had the characteristic brick-red discoloration caused by the fungus Rhizoctonia. Fusarium spp. were also isolated from several of these samples, the lower stem was black and tissue was collapsed. We will continue to see more seedlings develop these symptoms as the dry weather continues. If we do get some rain, the plants will develop roots above the lesions and may recover. Unlike Phytophthora, Rhizoctonia and Fusarium will girdle the plants at the soil line.

From areas of the state where there has been considerable rain, we have received some samples with Phytophthora. The one sample, it appears that with rain splashing, the zoospores were splashed onto the cotyledon and colonized the plant from the top down. The cotyledons and upper hyopcotyl tissue were brown and collapsed.
 

B) Check Fields for Two-spotted Spider Mites - Bruce Eisley CORN Questions

Two-spotted spider mites continue to increase and cause trouble in the dry areas of Ohio. Even though some of these areas received rain early in the week, it was not enough to help the mite problem. Reports on Friday indicated fields in north-central and south-central Ohio were being treated for spider mites. The weather report for the coming week has little or no rainfall and increasing temperatures. This will make the spider mite problems worse in the areas with less than adequate rainfall and the spider mite problem may move into other areas of the state.

Checks of soybeans in northwestern Ohio last Thursday found no mites or damage present.
 
Spider mite damage to soybean leaves

Refer to last week's newsletter (C.0.R.N. 99-13) for guidelines on when to treat for spider mites.

C) Bean Leaf Beetle Watch - Bruce Eisley CORN Questions

New adult bean leaf beetles will be emerging shortly and need to be watched. Areas where beans were planted and emerged early and areas where the overwintering population was large should be watched carefully for new adult emergence.

Treatment for bean leaf beetle at this time is based on the amount of foliage missing from the plant. The amount of foliage soybean plants can lose before treatment is warranted is based on the stage of the plant.

Rescue treatment for bean leaf beetle is justified when defoliation exceeds

40%      prior to bloom
15%      from bloom to pod-fill
25%      after pod-fill to plant yellowing

Additional information about bean leaf beetle can be found on the Internet at the following address: http//ohioline.ag.ohio-state.edu/icm-fact/fc-23.html
 
 
Bean leaf beetle adult on soybean leaf.

D) First Generation Corn Borer Levels Low - Bruce Eisley CORN Questions

European corn borer moths continue to fly but there is very little evidence of corn borer feeding damage in most fields. Surveys of fields in central and northwestern Ohio found little of any feeding damage by first generation corn borer.
 
European corn borer adults.

E) ALS Resistant Ragweed - Jeff Stachler  CORN Questions

Scout soybean fields 7-14 days after application of an ALS herbicide, such as Synchrony, FirstRate, or Raptor, to be sure common and giant ragweed have been controlled. If a field has poor control of common and/or giant ragweed where an ALS herbicide was used (especially FirstRate), please contact Jeff Stachler at 614-292-1393 or stachler.1@osu.edu. Do not respray with another ALS herbicide if poor control is observed. Just because common or giant ragweed are poorly controlled does not mean that the ragweed are ALS resistant. Greenhouse studies must be done to confirm the resistance.

F) Will This Be a Year to Double Crop Soybeans? - Clark Hutson CORN Questions

The possibility of an early maturing wheat crop for the second consecutive year has raised questions about the possibility for double cropping. There are two primary requirements for success in double cropping soybeans after wheat in Ohio. 1) An early wheat harvest made even earlier by harvesting wheat at 19 percent or higher moisture. When properly adjusted, newer combines can thresh wheat at 23 to 26 percent moisture. 2) Adequate soil moisture to get the beans germinated and continued moisture particularly later in the growing season.

This year's wheat harvest will likely be one to two weeks earlier than normal, satisfying the first requirement. As for the second requirement most of Ohio has been very dry through the early part of June. The wide spread rains that fell across much of Ohio in mid June could begin to satisfy the moisture requirement. Central Ohio and scattered areas around the state currently (mid-June) have a rainfall deficit of 1 to 4 inches. The long term forecast is for a dryer than normal summer in Ohio making double cropping even more risky than normal. Double cropping should not be attempted in areas that currently have a water deficit greater than 1 inch, according to Dr. James Beuerlein, OSU Extension Specialist, Soybeans and Small Grains.

Double cropping is not recommended in fields that have high levels of soybean cyst nematodes. Double cropping following wheat in these fields would negate the benefits of having wheat in the rotation for control of SCN.

Two additional items to keep in mind when considering whether or not to double crop. According to the Ohio Agronomy Guide: 1) Soils with low available water holding capacity such as soils that are poorly drained, somewhat poorly drained without tile, eroded, or sands are unsuitable for double cropping soybeans. 2) Double crop soybeans yields are reduced by about one bushel for each day planting is delayed. It is critical that planting take place as soon after wheat harvest as possible.

Last year under similar circumstances, producers who were able to take advantage of the early harvest and ample rains produced double crop yields that were quite satisfactory. Should this opportunity present itself again this year, producers should be prepared to begin wheat harvest as soon as conditions allow.

Additional cultural practices needed for successful double cropping can be found in the Ohio Agronomy Guide Bulletin 472, available at your county Extension office on the Internet at: http://www.ag.ohio-state.edu/~ohioline/b472/index.html.

G) Hail and Wind Injury to Corn - Peter Thomison CORN Questions

Severe thunderstorms accompanied by hail and strong winds have the potential to cause considerable damage to corn. The extent of the damage is dependent on the corn crop's stage of development. Hail affects yield primarily by reducing stands and defoliating plants. Defoliation usually results in most of the damage. The corn plant is generally little affected by hail prior to the 6 to 7 leaf stage because the growing point is below the soil surface and in the leaf whorl. However, once the growing point is elevated above the soil surface due to inter-node elongation, the plant grows rapidly and becomes increasingly vulnerable to hail damage with the tasseling stage being the most critical period.

Leaf damage by hail usually looks much worse than it really is, especially during the early stages of vegetative growth. Shredded leaves still have some capacity to contribute to plant growth. Plants not killed outright by hail usually show new growth within 3 to 5 days after injury occurs (i.e. if damage occurs prior to tasseling). For this reason, estimates of hail damage should be delayed several days to allow for this period of regrowth.

Based on estimates of the National Crop Insurance Association, at the 11-leaf stage if 50% of the leaf tissue is destroyed by hail, a corn plant loses only 7% of its yield potential; if 100% defoliation occurs, a corn plant loses 22% of its yield potential. At the 17-leaf stage, which occurs shortly before tasseling, a corn plant may lose up to 72% of its yield potential with 100% defoliation.

Note: The hail insurance adjustor's growth staging system counts leaves beyond the last visible collar to the uppermost leaf that is 40-50% exposed whose tip points downward - usually this is results in a leaf stage that is numerically 2 leaves greater than the "Leaf Collar Method" (e.g. a V6 plant according to leaf collar method would probably correspond to a 8-leaf plant according to the hail adjustor's method.)

Strong winds and heavy rain can also lodge or knock plants over, especially if the nodal root system is not fully developed (the "rootless" and "floppy corn syndrome"). The dry weather conditions we experienced recently in some parts of Ohio may have inhibited good nodal root formation and predisposed plants to such wind injury. This is a common problem in corn plants just prior to the rapid stalk elongation phase of development. Plants usually recover from such wind damage quickly with little impact on performance as nodal roots are established.

If winds cause plant stalks to snap and break over, plants are usually killed outright. During the rapid phase of vegetative growth the stalk tissue can be fairly brittle and stalks can be snapped by wind, especially when environmental conditions are very favorable for rapid stalk elongation. Certain hybrid genetics and herbicides can contribute to stalk "brittleness" or "green snap". According to recent studies on green snap, cultural practices that promote fast-growing corn are associated with the greatest green snap injury. The V5-8 stages and the V12 through tasseling stages are the most vulnerable stages.

A table relating percent yield loss to percent leaf defoliation is available in the "Corn, Soybean, Wheat and Alfalfa Field Guide" OSU Extension Bulletin 827. A portion of this table is listed below.
 
Percent yield loss based
on growth stage & defoliation		 Percent Leaf Defoliaton
Growth Stage* 25% 50% 75% 100%
7-leaf 0 2 5 9
8-leaf 0 3 6 11
9-leaf 1 4 7 13
10-leaf 1 6 9 16
11-leaf 1 7 12 22
12-leaf 2 9 16 28
13-leaf 2 10 19 34
14-leaf 3 13 25 44
*as determined by counting fully extended leaves.

For more detailed information on evaluating hail injury, consult "Assessing Hail Damage to Corn," National Corn Handbook Chapter 1"  contact Peter Thomison at 614/292-2047 if you would like a copy of this bulletin.

H) Horticulture & Crop Science Chair Interviews - Clark Hutson CORN Questions

The Department of Horticulture and Crop Science in the College of Food Agriculture and Environmental Sciences is in the process of selecting a new Chairperson. As part of this process each candidate will be presenting a seminar followed by a question and answer session for faculty, staff, industry representatives and other interested persons at two locations: 334 Kottman Hall on the OSU campus in Columbus and in the Fisher Auditorium Conference Room at the Ohio Agricultural Research and Development Center in Wooster.

Selection of the new department Chair will have an effect on the direction the department takes in the coming years. Therefore it is important that leaders in the Agronomy and Crop Sciences fields be a part of this process. Industry representatives and agriculture producers are encouraged to attend as many of these sessions as they can. The dates and times for the chair candidates' seminars are as follows:

Dr. Terry Riordan, Professor, Dept. of Horticulture, University of Nebraska-Lincoln
   10:45 a.m., Wednesday, June 23, Fisher Auditorium Conference Room, Wooster
   10:00 a.m., Thursday, June 24, 334 Kottman Hall, Columbus

Dr. Jerzy Nowak, Professor and Head, Dept. of Plant Science, Nova Scotia Agricultural College
   10:00 a.m., Monday, June 28, 334 Kottman Hall, Columbus
   10:15 a.m., Tuesday, June 29, Fisher Auditorium Conference Room, Wooster

Dr. Stephen Myers, Head and Extension Section Leader, Dept. of Horticulture, University of Arkansas
   10:00 a.m., Tuesday, July 6, 334 Kottman Hall, Columbus
   10:45 a.m., Wednesday, July 7, Fisher Auditorium Conference Room, Wooster

Dr. Mary Lewnes Albrecht, Professor and Head, Dept. of Ornamental Horticulture and Landscape Design, University of Tennessee
   2:00 p.m. Monday, July 19, 334 Kottman Hal, Columbus
   9:00 a.m. Tuesday, July 20, Fisher Auditorium Conference Room, Wooster

For additional information please contact Dr. Steven St. Martin, Department of Horticulture and Crop Science, The Ohio State University, at 614-292-8499 or by email: stmartin+@osu.edu


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: Anne Dorrance (Plant Pathology), Jeff Stachler (Weed Science), Peter Thomison (Corn Production) Ron Hammond (Entomology) and Bruce Eisley (Entomology)  Extension Agents: Dave Jones (Allen), Barry Ward (Champaign), Steve Prochaska (Crawford), Dennis Baker (Darke), Larry Lotz (Fayette), John Barker (Knox), Clark Hutson (Seneca) and Roger Bender (Shelby)

Editor: Clark Hutson        Web Editor: Clark Hutson

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

  | C.O.R.N. | Newsletter | Archive | Search | Questions? | Ohioline | Publications |