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In This Issue:
A) Late Season Soybean Diseases
B) Bean Leaf Beetles in Soybeans
C) Potato Leafhopper in Alfalfa
D) First Year Corn Rootworm Survey
E) ALS Resistant Ragweed
F) Herbicide Considerations When Using Soybeans For Silage and Hay
G) ODA Offers Free Testing of Forages for Nitrate Levels
H) Drought Information on the Web
I) Symposium on Biotechnology and Specialty Crops Offered Sept. 2 &
3, 1999
Sudden-death-syndrome, brown stem rot, charcoal rot, Diaporthe stem canker, Rhizoctonia stem rot and Phytophthora root rot are all diseases of soybeans which can cause early senescence. They are all similar in the field from a distance since where there are areas of yellow or chlorotic soybeans. These diseases are all caused by fungi and most are favored by wet weather during flowering. The first symptoms that may appear are yellow or chlorotic areas in-between the leaf veins which will then turn brown to tan. Leaves will defoliate early leaving stems, petioles and pods. How to tell which pathogen is responsible for each of these can be challenging.
Here are some key characteristics to look for when attempting to determine which disease is causing the problem:
1) Sudden-death-syndrome, is caused by Fusarium solani f. sp. glycinea. The tap root is very discolored and there are few, if any, secondary roots. The pith is white.
2) Brown stem rot, foliar symptoms are very close to Sudden-death-syndrome, but the tap root is clear and the pith is present and is a chocolate brown in color. This pith discoloration is not always present from the base of the plant up. Last year, we found the pith discoloration present in only the top part of the plant. Note: We have isolated both pathogens from the same plant.
3) Charcoal rot is a disease that has been reported in Ohio in years that we have very high soil temperatures, lesions will develop on the tap root and the area under the epidermis will appear to have very small, black dots or microsclerotia.
4) Rhizoctonia stem canker, will have a brick-red sunken lesion at the base of the stem.
5) Phytophthora stem rot symptoms include a brown to tan lesion growing from ground level, growing up the stem.
6) Diaporthe stem canker will have a brown to tan lesion girdling the stem approximately 1/3 up from the ground.
Surveys at the end of last week found varying numbers of bean leaf beetles (BLB) throughout the state. Surveys in soybean fields in central Ohio found bean leaf beetles approaching 6 per sweep in some of the fields with defoliation at 10-15 percent and pod feeding becoming evident. Other fields had less than one BLB per sweep and defoliation less than 5 percent and very little pod feeding. The important consideration at this time is to monitor fields closely and see what is happening with regard to bean leaf beetles. Even though the first generation population is falling, damage to pods from BLB and grasshopper feeding can be detected. This damage will likely increase as the second generation of BLB builds and foliage begins to yellow and drop from aging plants.
When scouting for bean leaf beetles, pay close attention to grasshopper populations, as well. It appears that grasshopper populations are being detected throughout the fields, not just the edges.
Information about treatment thresholds for BLB was given in the August 2nd issue of the CORN newsletter and can also be found in the Field Crop Pest Management Circular number 23 available at County offices and also on the WEB at: http://ohioline.ag.ohio-state.edu/icm-fact/fc-23.html.
Potato leafhopper populations remain high in alfalfa. Sweeps in our alfalfa plots at the Western Branch last week found very large numbers (20 per sweep) of adults and nymphs on 8 to 10 inch alfalfa. Third and fourth cuttings of alfalfa and new seedings should be monitored closely for this pest.
We are now entering the fifth week of the First Year Corn Rootworm Survey. As part of the survey, sweep net samples are taken in soybean fields, visual counts are taken in first year corn fields, and sticky traps are placed at both locations to catch Western corn rootworm beetles. WCR beetles remain low in soybean field sweeps. However, fields that are overly weedy, particularly with Giant Foxtail, can yield sweep net catches of 20-40 WCR beetles.
Visual counts of WCR in first year corn fields are up slightly these past two weeks compared to the first two weeks at most sites, but still well below the economic threshold.
Trap catches of WCR for the first two weeks are very low and under economic threshold at all sites monitored, with some signs of increased activity in Darke, Mercer, and Auglaize counties. Most traps catches have not been counted for weeks 3 and 4.
There appears to be an increase in trap counts for those traps that have been counted for weeks 3 and 4. Greg La Barge, Fulton County Ag Agent, reported a slight increase in the number of western corn rootworm beetles found on the traps during the second two-week trapping period. Traps in central Ohio also had a slight increase in beetle numbers from the prior two week trapping period but all traps, central Ohio and Fulton County, were still far below the economic threshold.
There are several fields around the state of Ohio that are suspected of having ALS resistant common or giant ragweed. If you have fields that had an ALS herbicide applied (such as Raptor, Synchrony STS, or FirstRate), and poor control of common and/or giant ragweed was observed please contact Jeff Stachler via e-mail stachler.1@osu.edu or by phone 614-292-1393. For a field to have ALS resistant ragweed, there should be plants in the field that were controlled right next to a plant that showed no injury symptoms and other plants that were severely stunted. We are interested in confirming the ALS resistance as well as looking for research sites for next year.
Dry weather has led to interest in areas of Ohio in using soybeans for silage or hay. Unfortunately, most soybean herbicide labels specify that treated soybeans should not be fed to animals as silage or hay. For soil-applied herbicides, only some of the older products, including Sencor, Lasso, Prowl, and Dual, permit these uses of treated soybeans. Among postemergence herbicides, only Basagran and FirstRate labels specify that soybean silage or hay can be fed. The Roundup Ultra label for Roundup Ready soybeans allows soybean silage or hay to be harvested, but is not clearly stated. Soybeans can not be harvested for silage or hay if Roundup Ultra is applied as a harvest aid. Poast and Poast Plus labels allow feeding of soybeans as hay, but not as silage.
The Ohio Department of Agriculture is offering farmers an opportunity to have forage tested for Nitrate levels for free. A one-gallon ziplock bag representative of a field or storage facility is the recommended sample size. The turn around time for samples will be 24 hours or less once a sample is received. Samples can be dropped off or mailed to ODA at 8995 East Main St., Reynoldsburg, OH 43068. Contact ODA at 1-800-282-1955 or your local Extension Office for more details.
An easy to reach index of management information for Ohio farmers facing drought conditions is located at www.ag.ohio-state.edu/~corn/drought99. Information on production, marketing and farm families can be found at this site.
A symposium on biotechnology and specialty crops will be held Sept. 2 through Sept. 3, 1999, in Reynoldsburg, Ohio. The "Agricultural Biotechnology and Specialty Crop Contracting Symposium" will feature topics of interest to crop producers and those involved in the grain processing industry.
"This symposium is particularly timely with current low commodity prices," said Robert Fleming, Ohio State University Extension District Specialist. "The topics discussed will provide ideas for those interested in increasing their income and spreading their risk through value-added crops. "The results of an external study by Sparks Commodities, Inc., on trends in biotechnology and its projected impact on agriculture will also be discussed. "This is the first time a symposium which combines topics on biotechnology and specialty crops with strong support from industry has been offered anywhere in the country," Fleming said.
The registration fee which covers program materials and meals is $80 and must be received by August 27. Registration materials are also available at your local Extension office. For more information, please contact Pam Brown at (614) 292-0315. The Agricultural Biotechnology and Specialty Crop Contracting Symposium is co-sponsored by The Ohio State University Farm Income Enhancement Program, The Ohio Farm Bureau Federation and The Ohio Department of Agriculture with support from the Ohio Corn Growers and Ohio Soybean Associations.
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Contact your local Ohio State University Extension Office or e-mail
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), Pat Lipps (Plant Pathology), Jeff Stachler (Weed Science); District Specialists: Jim Jasinski (Entomology), Bruce Eisley (Entomology), Curtis Young (Entomology); Extension Agents: Steve Prochaska (Crawford), Larry Lotz (Fayette), Dennis Baker (Darke), Greg LaBarge (Fulton), Roger Bender (Shelby), and Andy Kleinschmidt (Van Wert).
Editor: Andy Kleinschmidt 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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