CORN
Crop Observation and Recommendation Network

October 8 to October 14, 2001
C.O.R.N. 2001-34

In This Issue:

A) Dealing with Dandelions in Wheat
B) Bean Leaf Beetle/Bean Pod Mottle Virus on Soybean
C) Conduct Slug Assessment Now

A) Dealing with Dandelions in Wheat - Mark Loux and Jeff Stachler CORN Questions

The question of the week seems to be what to do with dandelions in fields where wheat has been planted, or will be planted as soon as soybeans are harvested. Dandelions are dense enough in areas that they are likely to reduce the wheat stand if not controlled soon. The options for dandelion are as follows:

• Where wheat has not been planted yet, either till the ground or apply glyphosate at a rate of 0.75 lbs acid equivalent/A (26 oz of Roundup UltraMax or 32 oz of Touchdown, Glyphomax, and other glyphosate products). Application of 2,4-D or dicamba immediately before wheat planting may reduce the wheat stand.
  
  
• Where wheat has been planted but has not yet emerged, apply glyphosate at the rate specified above.
  
  
• Once the wheat has emerged, control of dandelion becomes much more problematic. Labels for some 2,4-D products prohibit application in the fall. Labels for other 2,4-D products may not prohibit application in the fall, but as far as we know, all state that wheat must be fully tillered at the time of application. Wheat is not fully tillered in the fall, which seems to preclude 2,4-D application at this time. Dicamba is labeled for application to emerged wheat in the fall, but rates are too low to effectively control dandelion. We have observed effective control of seedling dandelions with Peak, and so it is possible that a mixture of Peak and dicamba after the 3-leaf stage of wheat would effectively suppress dandelions. We do not have experience with this treatment in our research, and producers/applicators should consult a sales representative before use. Double-crop soybeans cannot be planted after wheat if Peak is applied this fall or next spring. In addition, where the 0.5 oz rate of Peak is used, producers should strongly consider use of STS soybeans if the field is planted to soybeans in 2003. Harmony Extra and Harmony GT are labeled for fall application, but cannot be mixed with Banvel, and they probably do not have enough activity on dandelions.
  
  
• Where it appears that dandelions are not big or dense enough to have much effect on the wheat stand, herbicide application can be delayed until spring. At that time, 2,4-D or a mixture of 2,4-D plus dicamba could be used to suppress or control dandelions. Apply when daytime temperatures exceed 50 degrees for most consistent control.

B) Bean Leaf Beetle/Bean Pod Mottle Virus on Soybean - Ron Hammond and Anne Dorrance CORN Questions

We completed our survey of fields throughout Ohio for bean leaf beetle and soybean viruses, including looking for plants showing green stem syndrome where the pods are dry and brown while the stem remains green. Two to three fields in 10 counties were monitored and sampled during the summer. Bean leaf beetle populations were lower this year compared with 2000, although a few fields with significant pod feeding were seen. We found a few plants in all fields that were still green with malformed pods, a symptom of viruses. These plants were randomly scattered in the field, suggesting infections were probably seedborne.

Plants with green stem syndrome were observed in all fields, ranging from very few in western Ohio, less than 1% of total plants, to being very noticeable in northeast Ohio, between 10-20%. Plants with both types of symptoms were collected from all fields and brought back to the laboratory where they will be assayed for the virus this fall. We also collected back bean leaf beetles from these same fields during the summer which also will be assayed for the virus.

Three fields where Warrior insecticide was sprayed prior to or at soybean emergence to control the bean leaf beetle were also sampled. This was a trial to determine if insecticide can reduce bean leaf beetle populations and thereby reduce the level of bean pod mottle virus and mottled seed. Although each field had low to moderate levels of beetles in early summer, little evidence of the virus was evident in either sprayed or unsprayed areas at maturity. None of these areas had significant numbers of plants with green stem syndrome. Additionally, early reports from counties where these fields are located suggest very low levels of virus, and relatively low amounts of mottled seed.

C) Conduct Slug Assessment Now - Ron Hammond CORN Questions

Slug sampling can be done by placing about 10 square foot boards or roofing shingles throughout the field on the ground. Cups of beer can be placed in the soil underneath the boards to attract slugs. If beer is used, the shingles should be sampled the following morning. If only the boards are used, we would recommend sampling underneath the boards after a few days. Sampling would be most beneficial during warmer nights without frost, and is best done a few times during the fall.

Although specific thresholds are not available, knowing that a field has a low or large number of slugs will assist in management decisions next spring. If numerous slugs are found, there is a greater potential for slug problems in the spring which necessitates closer observations on those fields. If few slugs are found, the chances for problems are lower. However, we will continue to recommend to all no-till growers, especially those having a history of slug problems, that they monitor their fields for slugs in the spring no matter what they find in the fall.

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.

Editor: Andy Kleinschmidt        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.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868

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