C.O.R.N. Newsletter 2004-27

Dates Covered: 
August 16, 2004 - August 24, 2004
Harold Watters

Those yellow beans ARE NOT all SDS

Authors: Anne Dorrance

Driving around the state last week, we saw lots of yellow, early maturing beans in many areas of the state. Getting out of the car, walking into the fields, and digging up some of the plants provided a number of clues as to the real culprits causing early maturity this year. This crop has suffered due to too much rain in May, June and July. The average rainfalls across the state of were 172%, 126% and 100% of normal for these three months. And that is a lot of water. With excess water, conditions were favorable for flooding injury; root rots (Pythium, Rhizoctonia, Fusarium and Phytophthora) are present. What we are seeing now in these fields are the secondary effects of flooding injury but also all of the pathogens that have colonized these roots throughout the season. The plant has begun to switch its energy into filling the seed and does not have enough to keep defending itself against all of the pathogens.

Another cause of early yellow beans is the soybean cyst nematode. The most dramatic SCN field I have seen in this state was one on heavy low ground, the field had a yellow cast across the field, with some pockets a deeper yellow than others. Upon closer inspection, there was no root rot, but tons of bright white pearls (SCN females) on the roots. The bottom line, get out of the trucks and go look at these yellow, stunted spots. The beans are short this year, so the fields are fairly easy to walk through. Dig up plants in the center of the yellow areas and on the edges. First look for SCN, especially if the yellow areas are on the slopes or better drained areas of the field.

Next, see if you can pull off the outside covering of the roots. If this pulls off easily leaving a white root - flooding injury is a high probability. The drainage of the field needs to be assessed if this is the cause. Cut open the crown of the plant. In many of these plants the crowns are degraded. Last week we found some reddish-brown corky areas in this region. The reddish-brown corky regions are where Rhizoctonia established infections early in the year and now is finishing the plant off early. Adding a seed treatment compound that has activity against Rhizoctonia is recommended for these fields the next time soybeans are planted. If there are no roots, and there are no above ground symptoms, Phytophthora and Pythium are the likely culprits. Improving soil drainage and choosing varieties with higher levels of partial resistance are in order. We are finding some plants with Phytophthora stem rot and sudden death syndrome (SDS) in these fields but by far the primary problem was intitiated with the extended period of saturated soils occurred during May and June. We are now seeding the effects of all of this water. Yield effects will be determined at harvest.

Quadris and Warrior for 2004??

Authors: Anne Dorrance

We have received numerous questions this summer on the use of fungicides and insecticides on soybeans. I have very limited data on the application of fungicides on soybeans in Ohio.

First, in order to get ready for soybean rust (It is still not here), we began to examine some possible scenarios for its management, one of which was to combine fungicides at the timing of herbicide applications (V3 to V4). In one of our studies conducted in 2003, there was no significant impact of fungicide application on levels of brown spot (caused by Septoria) or yield. Previously, Ohio State University completed a number of studies which examined fungicide applications on soybeans at the mid to late flowering periods. These were studies which focused on the efficacy of fungicides for Phomopsis seed rot control. They found that yield increases of 2 bu/A were common, but more importantly seed quality was improved due to reductions in Phomopsis. This was determined to be of no economic advantage for beans raised for grain, but was recommended for seed producers to improve seed quality.

In the fields that I have walked this summer, we can find aphids, they are few and far between, but they are present. The impact of these sprays on the beneficial fungi and insects that feed on soybean aphids is unknown and how important these beneficials are in keeping the aphids at low populations is unknown. The only University data we have available is from Kentucky, and in some fields the Quadris-Warrior combination had a positive impact on yield and in other fields it did not. Due to the fact that there is only the limited data available and these results show variable responses, I cannot support this practice.

In addition, I as a professional plant pathologist and you as a practicing agriculturalist, have a responsibility to be stewards of our agricultural land. With this pact, we have promised to only use pesticides as needed in order that we may continue to use these tools to manage plant pests. Unwarranted spraying goes against this pact as well as against all of the integrated pest management strategies that we employ on our farms. We do not know what the primary or secondary effects are of these materials in soybeans. We are currently conducting research trials to determine these effects. This year we have established replicated field trials in 19 locations with the assistance of interested producers and county extension personnel to try and determine the impact of Quadris and Warrior on soybean yield in Ohio. Syngenta provided the product for these trials. This study will need to be done over two years, mainly because last year there were aphids and this year aphids are at very, very low populations. We will keep you posted on our progress.

What causes Tassel Ears?

Authors: Peter Thomison

This year I've received several inquiries about tassel ears in corn? Corn is the only major field crop characterized by separate male and female flowering structures, the tassel and ear, respectively. However, in most corn fields it is not unusual to find a few scattered plants with a combination tassel and ear in the same structure - a "tassel ear." The ear portion of this tassel ear structure usually contains only a limited number of kernels.

Tassel ears often appear on tillers (suckers) arising from plants with normal ears and tassels. These tassel ears are produced at a terminal position on the tiller where a tassel would normally appear. However, tassel ears may also be produced by individual plants. No specific cause of this condition is known but it often occurs in shorter spindly plants associated with delayed emergence and uneven crop development. Some hybrids may also be more prone to tiller under certain environmental conditions and these tillers may give rise to tassel ears. Tassel ears are frequently observed along the edges of fields where early season soil compaction and saturated soil conditions may have contributed to this abnormal growth and development. Tassel ears are a reminder that the male and female parts of the corn plan are structurally very closely related. Wild progenitors of corn -teosinte spp. have complete flowers tassels and silks together. These can be crossed with Zea mays (normal corn).

There has been some speculation that a fungal disease called "crazy top" may be responsible for this abnormal ear condition. Crazy top does affect the appearance of tassels and ears but the symptoms are distinctly different from those of the tassel ear phenomenon. Crazy top causes the tassel and/or the ear to become leaf-like. In severe cases, the whole top of a plant and ears are replaced with a mass of leaf-like structures. Visual symptoms and more details concerning crazy top are available online at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/corn/crazytop.htm

For more information on tillering, check out fact sheet AGF-121-95, "Corn Growth and Development - Does Tillering Affect Hybrid Performance?" It's available online at http://ohioline.osu.edu/agf-fact/0121.html

Dr. Bob Nielsen, extension corn specialist at Purdue University, has an article with excellent pictures of plants with tassel ears - “Tassel-Ears in Corn” available online at http://www.agry.purdue.edu/ext/corn/news/articles.04/TasselEars-0713.html.

Giant Ragweed Poking Through Corn and Soybean Canopies

There are many factors that have made giant ragweed a troublesome weed this season. Some of them include:
1. Reliance on a single herbicide application, especially preemergence only treatments in corn, but also the single glyphosate application in Roundup Ready soybeans.
2. Early planting, which means more plants must be controlled while the crop is growing.
3. Lots of rainfall, which has allowed continual germination of giant ragweed this season and faster degradation and/or leaching of preemergence herbicides.
4. Larger than normal giant ragweed plants at the time of application, due to short windows of application caused by excessive wind and rain. Big plants are harder to control.
5. ALS-resistant giant ragweed. More has shown up this year with the increase in non-GMO soybeans.
6. Shorter than normal soybeans due to stressful growing conditions.
7. Spotty or irregular stands of corn and soybeans due to too much rainfall. This allows for a more open canopy that allows for later germination.
8. Insect tunneling of large giant ragweed plants. Giant ragweed control can be reduced with the use of postemerge translocating herbcides if insects are present in the stem. Spraying smaller (< 8 inch) giant ragweed usually reduces the problem.
9. Spraying giant ragweed after 9:00 P.M. through 6:00 A.M. Research has shown the most effective control of giant ragweed with glyphosate is between 9:00 A.M. and 6:00 P.M.
10. Adding manganese to glyphosate along with a replacement AMS product (at least when used at less than 17 pounds of dry AMS/100 gallons of spray mixture).
11. For the northern part of Ohio and other areas not accustomed to giant ragweed, there may be a shift in the population to longer season germination rather than a short early spring germination period.

In fields with giant ragweed showing above the crop canopy, there are currently only three options available for most fields. One is to cut out these plants so they do not produce seeds. This can have a dramatic effect upon the future population, especially if the plants are herbicide resistant. When weed seed is produced from herbicide-resistant plants, then you are greatly reducing the utility of that herbicide for future years. Some giant ragweed populations began flowering this past week, so immediate removal of those plants are necessary to stop maximum seed production.

A second option is to apply glyphosate or Gramoxone Max as a harvest aid. The greatest advantage of this application is to allow for easier harvest. There is usually little effect on the giant ragweed seed production. Although glyphosate will have the greatest impact on the viability of future seeds compared to Gramoxone Max, especially when applied in early September.

The last option is to start planning for next year's herbicide program in these fields. The most consistent and effective giant ragweed control in corn and soybeans is achieved when using a planned preemergence followed by postemergence herbicide program. The three greatest benefits to this program is a wider window for the postemergence application, usually smaller giant ragweed for the postemergence application, that will be easier to control, and more consistent control. It only takes about one giant ragweed per square foot to reduce corn and soybean yields when it emerges at the same time as the crop.

Soil Tests for Plant Available Phosphorus

Over the last few years questions have arisen about the tests for soil phosphorus (P), especially the relationship between the Bray-Kurtz P1 and the Mehlich 3 soil phosphorus tests. Both tests have been used for Ohio soils and measure plant available P, not the total P concentration in the soil. The Bray-Kurtz P1 test has often been called just the Bray P1 test. The following is a discussion of these tests and includes basic information about the development of successful soil tests.

Purposes of a Soil Test:
A useful test should be able to separate soils that are deficient in P from those that are sufficient in P in regard to optimum plant growth. In addition, information about plant response to the application of fertilizer P should be part of the test. Several tests have been developed for measuring plant available P in the soil. The kind of test that should be used depends on the soil. Consequently, appropriate P soil tests are based on the kind of soils that occur in various regions of the United States. Many years of research are required to develop a useful soil test for the soils of a region.

Development of a Soil Test:
The development of a soil test involves two primary aspects of study. The first aspect involves a study to establish the chemical extracting solution that shows the highest correlation (strongest relationship) between the concentration of P extracted from the soil to the amount of P taken up by the plant. In this way, the extracting solution relates what is in the soil to what is used by the plant. This research is usually done under greenhouse conditions where many different extracting solutions are evaluated on different soils, and usually for many different plants. This has been the case for both the Bray-Kurtz P1 and Mehlich 3 extracting solutions for the soil P tests.

The second aspect involves calibrating the soil test to determine the relationship between the concentration of P in the soil to a response of the crop under study, usually bushels/acre or tons/acre of yield. This provides information about the optimum crop response (yield) at a given concentration or range of concentrations of P in the soil. The determination of an estimate of optimum crop yield at a given soil P concentration will allow for the separation of soil P concentrations into deficient and sufficient categories. In addition, if the soil is in the P deficient category, the calibration research will provide information on how much increase in crop yield will likely be obtained with increases in the concentrations of soil P. From the calibration research, a recommendation for applying specific amounts of fertilizer P to the soil can then be developed. The calibration work is done under field conditions and involves replicated field research on different soils.

Bray-Kurtz P1 Test:
The Bray-Kurtz P1 test was developed in 1945 at the University of Illinois by Dr. Bray and Dr. Kurtz. The correlation with plant uptake of P ranges from 0.70 to 0.94 for the soils of the North Central Region of the USA. The detection limit of the test is 1 part per million (ppm) P and the reproducibility is plus or minus ( + ) 10%. It is recommended by the USDA North Central Regional Soil Testing and Plant Analysis research committee (NCR-13) for use on soils with pH 7.0 or less. The Ohio State University fertilizer recommendations for agronomic crops grown in Ohio soils are based on this soil P test.

Mehlich 3 Test:
The Mehlich 3 test for plant available P in the soil was developed by Dr. Mehlich at North Carolina State University in 1984. It was a modification of his earlier tests, Mehlich 1 and Mehlich 2. The test has been referred to by some as the “Universal Extractant” method since both P and K can be determined in the same solution at the same time by appropriate laboratory instrumentation. Limited crop response work on soils of the North Central region has shown the correlation with P uptake by the plant to range from 0.83 to 0.99. After many years of study, the NCR-13 Committee approved the Mehlich 3 test for North Central soils that have a pH of 7.0 or less. The detection limit of the test is 1 ppm with a reproducibility of +10%.

How do the two test compare?
It has been found across most of the soils of the North Central Region that generally the Mehlich 3 tests extracts more P from the soil than the Bray-Kurtz P1 test. Limited research in Ohio has shown that on samples of Crosby soils the Mehlich 3 test extracted, on the average, 30 ppm P, compared to 19 ppm with the Bray-Kurtz P1 test on the same Crosby soil samples. On Ohio Hoytville soil samples, Mehlich 3 extracted 30 ppm P, compared to 16 ppm with the Bray-Kurtz P1 test. Although the data is somewhat limited, a linear relationship can be determined across a range of soil P concentrations from results of the two tests.

What about making P fertilizer recommendations from the Mehlich 3 test?
Since there is limited field calibration of the Mehlich 3 to crop response for Ohio soils, and since the fertilizer recommendations for agronomic crops are based on the Bray-Kurtz P1 test, soil testing laboratories that use the Mehlich 3 test should make an estimation of what the P concentration would be if the Bray-Kurtz P1 test were used. This can be done by doing both tests on hundreds of soil samples and from this information develop a linear equation describing the relationship of the P concentrations. This is the best approach until field research can be done that evaluates crop response to the soil P concentration as determined with the Mehlich 3 test. However, it has been emphasized by the NCR-13 committee that a laboratory should not run the Mehlich 3 test and then refer to the results as being from a Bray-Kurtz P1 test. It is important in the future that fertilizer recommendations based on for the Mehlich 3 test be developed from actual field crop response calibration work on as many soils as possible.

Ohio Ag Manager Newsletter Makes its Debut

Authors: Chris Bruynis, David Marrison

OSU Extension is pleased to announce that the release of the Ohio AG Manager newsletter and web site. The Ohio Ag Manager is a publication designed by OSU Extension Specialists and Extension Agents for Ohio's Farm and Business Community. Its goal is to deliver information relevant to the management of agricultural businesses in short, succinct articles. The newsletters design concept is to provide managers each month with 7 to 10 articles on issues and trends that could impact the agricultural industry. Each of these articles is linked to complete reports or web sites containing more detailed information. This design allows the reader to retrieve details on topics and issues that are important to the management of their agribusiness.

The Specialists and Extension Agents at The Ohio State University encourage you to explore the Ohio Ag Manager website located at: http://ohioagmanager.osu.edu

Individuals that would like to receive the monthly newsletter sent to their individual email accounts should send a blank e-mail message to: ohioagmanager-on@postoffice.ag.ohio-state.edu

Tri-County Agronomy Field Day August 26th

Authors: Howard Siegrist

Fairfield County will be the site for this year's Tri-County Agronomy Day. The program includes field demonstrations of current agronomic technologies with on-site experts to answers questions on a variety of topics.

Grain producers and certified crop advisors are encouraged to attend this premier agronomic program on August 26 from 1 to 7:30p.m. to highlight:

Tillage demonstrations and comparisons - With Ken Ferrie
Crop biotech and late season crop issues
High tech high profit wheat production
The do's & don'ts of using chicken manure to increase yields
Remote sensing & Precision Ag
USDA'S new conservation security program and soil quality testing

Sessions start promptly at 1:00 p.m. and continue on a regular basis through 5:00 p.m. Registration will begin at 12:30 with shuttles running all afternoon. A $5.00 registration fee payable the day of the program covers all sessions and a pork chop dinner, which will be served at 6:00 p.m. The evenings featured speaker is Ken Ferrie, Farm Journal field agronomist who oversees the test plots in the Farm Journal Field Test program. Ferrie applies his extensive, cutting-edge knowledge and his systems approach of farming to the plots. In addition to his work with the Farm Journal, he operates an independent agronomic consulting business in central Illinois.

The Cupp and Claypool Farm Families are hosting the tour site, which is located at 3255 Lancaster-Circleville Road Lancaster, OH.

Four hours of Continuing Education Credits for Certified Crop Advisors will be offered.

The Tri-County Agronomy Field Day is sponsored by the following Fairfield, Licking, Pickaway and Perry County organizations: OSU Extension, Soil & Water Conservation Districts, Natural Resource Conservation Service and Farm Service Agency. Corporate sponsorships include Farm Credit Services and others that will be announced at the field day. Anyone who wishes to receive additional information can contact Licking OSU Extension Office at 740-349-6900 or e-mail siegrist.1@osu.edu for a copy of the promotional flyer, which includes program speakers and a map.

Archive Issue Contributors: 

State Specialists: Pat Lipps and Anne Dorrance (Plant Pathology), Robert Mullen and Maurice Watson (Soil Fertility), Jeff Stachler (Weed Science), Bruce Eisley (Entomology) and Peter Thomison (Corn Production). Extension Agents and Associates: Harold Watters (Miami), Glen Arnold (Putnam), Roger Bender (Shelby), Steve Foster (Darke), Howard Siegrist (Licking), Greg Labarge (Fulton), Gary Wilson (Hancock), David Marrison (Ashtabula) and Chris Bruynis (Wyandot).

About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.