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

CORN
Crop Observation and Recommendation Network

October 28 - November 11, 2002
C.O.R.N. 2002-37

In This Issue:

A) Poor Yields, Stunted Plants, and Early Maturity
B) How Reliable Will This Year's Test Plot Data Be?
C) Corn Rootworm Trapping in Soybeans in 2002
D) Use of Soybean Foliage/Residue for Hay - Herbicide Restrictions
E) Recommendations for Late Alfalfa Harvest

A) Poor Yields, Stunted Plants, and Early Maturity.... - Anne Dorrance, Dennis Mills, Richard Riedel, Nancy Taylor CORN Questions

Were these some of the symptoms of plants in your fields? When you were driving the combine, did you hit pockets where the yields dropped 5 to 10 bushels, but otherwise the plants looked the same. These are all symptoms of Soybean Cyst nematode. Compound these factors with the effects of drought and in some fields the presence of sobyean cyst nematode were even more dramatic this past growing season. If you have pockets of low yields, especially on the sides and tops of hills, areas where drainage is not an issue, you should sample for soybean cyst nematode this year. The soybean cyst nematode will be at its highest populations at the end of harvest. This is the best time to detect the nematode if it is present as well as to make management decisions.

The BEST management strategy for soybean cyst nematode is ROTATION. We exploit the fact that this pathogen can only reproduce on a few crops. Each time we rotate to a non-host crop, we starve the nematode and their populations decline. However, in each single growing season, only about ½ of the eggs will hatch. So with one year of wheat, the populations are reduced by ½, the following year with corn another ½. Often this brings the populations down to levels where a bean with SCN resistance or a susceptible bean can then be planted.

This nematode will feed and move through the soybean roots during the early phases of its life cycle. The female, will become sedentary and establish a feeding site on the root as her eggs develop. Resistance is measured in soybeans as the number of females that develop on roots compared to the susceptible control. In plainer english, in a susceptible variety as many as 200 females may develop on soybeans in these greenhouse tests, where on a resistant variety, only 15 may develop. The key is that some do develop. This is an animal species, there is considerable variability for appetite for different sources of resistance within any given field. No, you do not need to have your field race typed, but if soybean cyst nematode is a problem, you have the best information by monitoring the populations following a soybean planting. Basically, create your own database for each field, by monitoring varieties planted, yields and soybean cyst nematode populations over time.

For example, if you planted a SCN resistant variety. Three things can happen, populations drop just like they do with corn or wheat; no change; or an increase in population similar to a susceptible bean. If the populations increase, do not plant that variety again, and immediately change that field from soybean production to non-host crops. If the populations did not drop - this indicates that nematode populations are beginning to adapt to that type of resistance, add an additional year of a non-host crop to bring the numbers below the economic threshold level for a susceptible bean. Plant a SCN susceptible bean in that field - then return with a SCN resistant bean. This helps to keep those nematodes that can reproduce on resistant beans at lower populations. If the SCN populations dropped - continue with the rotation plan. The main message here is to sample-sample-sample and follow those populations over time and make your variety selection decisions accordingly.

Analysis of soil samples for SCN submitted by Ohio growers from 1998 to present represents only 2% of the cropland acres and indicates that about 8% have very high levels of SCN (more than 5,000 eggs/200 cc), 6% have moderate levels (2000-5000 eggs), 18% have low levels (200 - 2000 eggs) and 68% have none to trace levels (0 to 200 eggs). This summer the C. Wayne Ellett Diagnostic clinic reported some alarming SCN egg counts from two samples, 25,600 and 36,000.

Symptoms of SCN damage in Ohio were more evident in 2002 with the drought conditions, which range from stunted, yellow plants, to plants that turn yellow early, to soybeans that do not reach their yield potential. The best way to manage SCN is to know which fields have nematodes and how many nematodes are present. The best time to sample fields is in the fall after soybeans are harvested. Soil samples can be sent to some private labs or to The Ohio State University, C. Wayne Ellett Plant and Pest Diagnostic Clinic. Fees for SCN testing will be: for a single shipment of soil samples from an individual farm, $15.00 for the first soil sample, $10.00 for each additional soil sample in the shipment.

C. Wayne Ellett Plant and Pest Diagnostic Clinic
110 Kottman Hall
2021 Coffey Road
Ohio State University
Columbus, OH 43210-1087
614-292-5006
http://plantpath.osu.edu/cweppdc/cweppdc.html

SCN Soil Sampling Instructions:
1. Use a 1-inch diameter soil probe to collect soil samples (6-8 inches in depth)
2. Following a zig-zag pattern, collect 10-20 soil cores per 10-20 acres
3. Collect cores from areas of similar soil type and crop history
4. Dump cores from each 10 to 20 acre area into a bucket or tub and mix thoroughly
5. Place 1 pint (2 cups) of mixed soil in a soil sample bag or plastic zippered bag and label with a permanent marker
6. Store sample in cool, dark place until shipped to a lab doing SCN analysis.

A new listing of SCN resistant varieties offered in Ohio for 2003 is now available at:
http://www.oardc.ohio-state.edu/ohiofieldcropdisease/soybeans/scn.htm

B) How Reliable Will This Year's Test Plot Data Be? - Peter Thomison CORN Questions

Ohio's corn crop experienced a host of problems in 2002, including excessive soil moisture at planting, early season frosts, soil compaction, high temperatures, mid to late summer drought, and severe flea beetle infestations. Agronomists often question the value of test plot data in years like 2002 when adverse growing conditions severely limit yield potential. Severe stresses can undermine the value of test plot performance data.

The validity of test plot results depends primarily on whether effects of the varied stress conditions are uniform across test plots. If not, test plot data may be questionable. To be certain that effects of stress were fairly uniform, it would be necessary to monitor test plots on a regular basis to determine crop response to the various stresses as they occurred; however, such monitoring was probably unlikely in many test plot fields.

Another problem with test plot results is that the various yield limiting factors may accentuate the natural "variability" already existing in the field, and may thereby further "mask" the true treatment effects that are being compared. Stress conditions coupled with slight differences in soil organic matter, drainage, weed control, etc. across a field may magnify differences in crop performance.

If one assumes that the varied stress conditions affected test plots uniformly within a field, then interpretation of test plot data becomes an issue. This issue can be especially relevant when evaluating results of a hybrid performance trial severely affected by drought. Did a hybrid yield well under drought stress because it genuinely possesses some drought resistance or because it "escaped" the drought by flowering before or after the worst of the stress? If it was the latter, then the hybrid's superior performance may be of limited value under different drought conditions in the future. In past years, we have sometimes observed that if a drought occurs late in the season then early maturing hybrids will have an advantage over later maturity hybrids; if the drought occurs earlier, but is broken by rains later in the season, then the full season hybrids may have the advantage.

Test plot information this year can still be very useful but take precautions. Results from single on-farm strip tests should not be used to make a decision on adoption of a treatment or hybrid. Even replicated data from a single test site should be avoided, especially if the site was characterized by abnormal growing conditions. Use test plot data from multiple sites (and preferably from at least 2 years of testing) and inquire about the weather patterns and conditions associated with the results. Look for consistency in a product or hybrid's performance across a range of environmental conditions.

C) Corn Rootworm Trapping in Soybeans in 2002 - Bruce Eisley & Ron Hammond CORN Questions

Ohio State University Extension personnel in 2002 continued to monitor for first year corn rootworm (FYCR) which is a biotype of the western corn rootworm (WCR) that deposits eggs in soybean fields that can damage corn planted in that field the next year. This is the fifth year that monitoring has occurred. The program used Pherocon AM yellow sticky traps which are placed in soybean fields (at least 4 traps per field) on a biweekly schedule from mid-July through August to monitor adult rootworm activity. Sixty-four fields in 19 counties were trapped with Pheroncon AM traps in 2002. All of the counties changed traps on a biweekly schedule except Van Wert which changed their traps on a weekly schedule.

A summary of the average catches of WCR adults per trap per day from the 2002 growing season is presented in Table 1. The catch for a given field represents the average catch of adult WCR from traps over a six week period. The average catch for a county represents the total number of fields monitored in a given county. Even though the number of fields sampled is small, it gives an indication of the WCR populations in soybeans in 2002 as compared with previous years.

Beetle numbers on traps were higher in all counties in 2002 as compared with previous years. Collection of 2 or more WCR beetles per trap per day in a soybean field is presumed to indicate a potential for economic injury at a root rating of 3 if corn is planted the following year. Based on this fact, only 1 field (in Van Wert County) exceeded the 2 beetles per trap per day. There were several other fields in Van Wert and Allen, Mercer and Defiance Counties that had greater
than 1 beetle per trap per day. Fields in the other counties less than 1 beetle per trap per day.

A soil insecticide treatment for FYCR may be warranted if WCR beetle numbers per trap per day are greater than 2 or more beetles over a six week period. If a field was not trapped in 2002 but observations in July and August found a large number of WCR beetles in the fields at that time, then a soil insecticide might be justified. Conversely, if WCR were not observed in soybeans in high numbers in July and August then a soil insecticide treatment in 2003 probably cannot be justified.

If soil insecticides are applied for rootworm, then check strips should be left to determine if the treatment was warranted or not.

Trapping in soybeans with Pherocon AM yellow sticky traps needs to continue in 2003 to monitor for FYCR. At least 4 traps need to be placed in fields in mid-July and changed weekly through August (a six week trapping period) to determine WCR beetle levels so that if the field goes to corn in 2004, a decision can be made about using a soil insecticide.

D) Use of Soybean Foliage/Residue for Hay - Herbicide Restrictions - Mark Loux CORN Questions

Few soybean herbicide labels allow treated soybeans to be harvested for forage or used for hay. Soybeans may be used for these purposes if Boundary, Prowl, or Sencor were applied preemergence. Other preemergence herbicides prohibit these uses of soybeans. Soybeans may be used for forage or hay if Basagran, FirstRate, Roundup UltraMax, or Glyphomax were applied postemergence. Soybeans treated with Touchdown may not be used for forage or hay. For other glyphosate formulations, consult the label or a manufacturer's representative for information on the harvest restrictions for soybeans used as forage or hay.

E) Recommendations for Late Alfalfa Harvest - Gary Wilson CORN Questions

In a year of very low forage supplies, there has been great consideration to look at a late hay or alfalfa harvest. If a late fall harvest must be made, it should be delayed until a killing frost (25 degrees F. for several hours).
Suggestions to minimize the problems of this late harvest are as follows:

Alfalfa stand should be well established - NOT a new seeding.
Field should be well drained.
Soil must have a high level of fertility that is maintained with annual fertilization. Fall application of fertilizer, especially potassium, is very important.
Cut four inches high for this late cut, to provide some insulation against winter hazards and to assist in snow retention.
If possible, also mulch with strawy manure or other appropriate mulching material following the late harvest. This will provide winter protection and reduce heaving caused by alternate freezing and thawing.
Snow cover acts as an insulator of the soil and plants. Thus, this practice of late harvest may be more feasible in areas of Ohio that historically receive larger, longer-lasting quantities of snow.

Also, One should choose to either make hay as haylage or baleage at this time of year since curing would be difficult.

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.

State Specialists: Pat Lipps, Anne Dorrance, Dennis Mills, Richard Riedel & Nancy Taylor (Plant Pathology), Ron Hammond & Bruce Eisley (Entomology), Mark Loux (Weed Science), Peter Thomison (Corn Production) District Specialist: Ed Lentz (Agronomy) Extension Agents: Howard Siegrist (Licking), Harold Watters (Miami), Roger Bender (Shelby), Clark Hutson (Seneca), Gary Wilson (Hancock), Barry Ward (Champaign)

Editor: Barry Ward 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.