C.O.R.N. Newsletter 2009-32

Dates Covered: 
September 21, 2009 - September 28, 2009
Wesley Haun

Harvest Planning – When to Harvest Those Problem Fields

Authors:Anne Dorrance

We have a number of fields that have high levels of Sclerotinia stem rot, SDS and SCN this year. Each of these diseases is readily spread with soil or trash that moves on equipment. This is especially true of the sclerotia formed by the Sclerotinia fungus in fields with Sclerotinia stem rot. The hard black irregular shaped sclerotia will form both inside and outside of the stem. Combines are great machines and can be especially efficient at moving things around. So as I see it, there are two choices in prioritizing which field to harvest first. A) Harvest problem fields first, they are maturing early, and then clean the combine before moving to good fields. B) Alternatively, these problem fields could be harvested last and then clean the combine one time before storing. The caveat with this – especially for those areas that received substantial rains during the season, is that Phomopsis can also be a problem. Phomopsis seed rot has been a problem in a few areas of the state where substantial rains persist through the maturation process (seed filling growth stages) and on susceptible varieties. If the seed becomes subjected to repeated rainfall events, this increases the likelihood that Phomopsis can then add to the problems. You’ve got to weigh the different options for your own operation, but by all means have a safe harvest.

"Blunt Ear" Syndrome Appearing in Ohio Corn Fields

Authors: Peter Thomison

I have received several reports in recent weeks of “beer can” ears, an abnormal condition in which corn ear length is markedly shortened. This ear abnormality has also been referred to as ear stunting or “blunt ear” syndrome. This year the anomaly has also been reported in Indiana (http://www.kingcorn.org/news/timeless/BluntEars.html) and Pennsylvania (http://fcn.agronomy.psu.edu/2009/fcn0925.cfm#c).
Two key visual symptoms associated with ear stunting are ears that are much shorter than normal and a considerable section of the ear tip that has not produced kernels. This latter symptom appears to be related to poor pollination, perhaps the result of tight husks preventing and/or delaying normal silk emergence. These husks tightly cover stunted ears and may not provide adequate space for silks to emerge normally. Beer can problems may be often associated with multiple ear shoots per node. Several nodes of the affected plant may exhibit stunted ears and multiple ears per node. To compare beer can ear symptoms with other ear development problems check our abnormal ears web page [online]https://agcrops.osu.edu/corn/documents/AbnormalCornEarsPoster_000.pdf
Corn plants with stunted ears generally appear healthy with normal husk formation and growth. However, husks may appear somewhat pointed, probably because husks were more tightly wrapped around the much smaller ear enclosed. At harvest, plants with stunted ears often turn purple due to an accumulation of sugars in the leaf and stalk tissue. Ear stunting is often localized within fields (e.g. head rows and border rows or patches within fields) with only a small percentage of plants (<1-5%) affected.
Little is known concerning possible causes of this abnormal ear development. The problem may be related to a low temperature stress or shock during ear development between the 5-leaf collar stage and 12-leaf collar stage. In 1992, a year during which corn ear stunting was widely observed across the Corn Belt, the only common factor shared by fields exhibiting ear stunting problems seemed to be low temperature (down to near freezing) in late June during ear size determination. The localized occurrence of beer can ears within a field supports speculation that some stress may be impacting ear development of a limited number of plants, which are at a highly sensitive growth stage.
No consistent relationships between soil fertility levels, herbicide programs or corn diseases are evident. Hybrids also appear to differ in susceptibility to the problem.
In 2007, and to a lesser extent 2006, there were reports of “arrested ear” development in several Corn Belt states. Arrested ears were characterized by a range of symptoms, and in some cases seemed to resemble beer can ears. However, there were some important distinctions. Some ears exhibited varying degrees of stunting with limited kernel formation. Some ear shoots carried either no ear or only the short remnant of an ear. Often silks were absent or limited. Some of the most pronounced arrested ear damage was associated with foliar fungicide applications made with ground equipment during the two week period prior to tasseling. In various postmortem assessments, it was noted that arrested ear injury frequently occurred in fields where the foliar treatments included non-ionic surfactants. Now, there is preliminary evidence from Purdue University and University of Illinois evaluations conducted in 2008 that suggests that the cause of some of these arrested ear problems may actually be due more to surfactants than fungicides.
For more information about these ear development anomalies, check the following online articles:
Nafziger, E. 2008. More ear oddities, and a possible cause. The Bulletin, Univ. of Illinois. [on-line]. Available at http://www.ipm.uiuc.edu/bulletin/article.php?id=1033
(URL accessed 9/21/09).
Nielsen, R.L., W. Wise, C. Gerber. 2008. Arrested ears resulting from pre-tassel applications of pesticide & spray additive combinations. Corny News Network, Purdue Univ. [on-line]. Available at http://www.kingcorn.org/news/articles.08/ArrestedEars-1209.html (URL accessed 9/21/09).
Nielsen, R.L. (Bob). 2009. Blunt Ear Syndrome....Again. Corny News Network, Purdue Univ. [online] http://www.kingcorn.org/news/timeless/BluntEars.html. (URL accessed 9/21/09).
Roth, G. 2009. Arrested Ear Development. A Nagging Problem That Won’t Go Away. Penn State Field Crop News [online] http://fcn.agronomy.psu.edu/2009/fcn0925.cfm#c (URL accessed 9/21/09).
Thomison, P. and A. Geyer. 2007. Abnormal corn ears. Ohio State University Extension. ACE-1. [online] https://agcrops.osu.edu/corn/documents/AbnormalCornEarsPoster_000.pdf
(URL accessed 9/21/09).

Timing Fall Herbicide Treatments Based on Weed Life Cycle

Authors: Mark Loux

Fall herbicide treatments can have a range of goals, from control of warm-season perennials prior to crop harvest to control of winter annuals that make for a messy seedbed next spring. We receive questions about the optimum timing of fall herbicide treatments, and while optimum timing can vary based on life cycle, we can roughly lump the various life cycles into one of two categories:
1) Must be treated before frost, which pertains to all warm-season perennials, including johnsongrass, pokeweed, milkweeds and hemp dogbane, and horsenettle. The first frost will cause these weeds to shut down, if they have not already matured and senesced. Herbicides are no longer effective after this occurs.
2) Can be treated after frost and in some cases even after a hard freeze. Winter annuals, biennials, and cool-season perennials fit into this category, and they are often most effectively controlled when herbicides are applied between mid-October and mid-November.
Winter annuals, including chickweed, purple deadnettle, mustards, and cressleaf groundsel among others, emerge in late summer into fall. They survive frost and are still sensitive to herbicides even after cold weather in December, based on our research. Herbicide activity in these weeds slows down in cold weather, but the effective treatments still eventually kill emerged weeds. It’s not necessary to wait until frost to apply herbicides, except that: 1) treatment too early in fall can miss the plants that are still emerging; and 2) for treatments that include herbicides with residual activity (metribuzin, simazine, Canopy, etc), the soil temperatures in early fall are still warm enough for herbicide degradation to occur. This reduces the amount of herbicide present in spring, potentially allowing weeds to emerge earlier in spring than intended. It’s not necessary to use glyphosate for control of winter annuals, unless winter annual grasses are present. They can be controlled with combinations of 2,4-D and either glyphosate, metribuzin, Canopy, Basis, or simazine (see the 2008 article on fall herbicide treatments in the C.O.R.N. archive for more specifics on treatments – not much has changed since then except a decline in glyphosate prices).
Biennials, such as poison hemlock and wild carrot, are most effectively controlled in the fall at the end of their first year of growth, when they exist as a low-growing rosette. We do not have experience trying to control these with herbicides in winter under very cold conditions, but they are dormant then and should probably be treated in the mid-October to mid-November application window. Fall treatments for biennial weeds will generally be most effective when they include glyphosate and 2,4-D.
Cool-season perennials include dandelion, Canada thistle, and quackgrass. Herbicides can be more active in these weeds after a frost, which triggers the plant to increase movement of carbohydrates into the roots or rhizomes. Systemic herbicides move to these same areas with the translocating carbohydrate. The other key to effective control is to make sure the weeds have recovered fully from harvest, late summer mowing or earlier droughty conditions, and are fairly sizable. Canada thistle should be 8 to 12 inches tall for best results, and dandelion should have a healthy rosette with a number of fully expanded leaves. Delaying herbicide application until late October or November will allow more time for the weeds to recover. While winter annuals can be treated into early winter, the colder conditions will reduce herbicide activity in cool-season perennials. Cool-season perennials will generally be most effectively controlled with combinations of glyphosate and either 2,4-D or dicamba, although combinations of 2,4-D with Basis or Canopy are among the most effective treatments on dandelion. Glyphosate is most effective on Canada thistle when applied without other herbicides, and is really more effective than 2,4-D or dicamba on dandelion in the fall. However, combinations of glyphosate and 2,4-D will be more effective for control of the many populations of glyphosate-resistant marestail.

Hessian Fly and Wheat Planting Dates

Authors: Ron Hammond, Andy Michel, Bruce Eisley

This is a reminder for wheat growers to plant their wheat after the Hessian Fly Safe date for your county. The following web site from Bulletin 827 gives the fly safe date for all of Ohio: http://ohioline.osu.edu/b827/0004.html . These dates vary, beginning now for northern counties (September 22-23) to October 5 for the southern most counties. Planting within the first 10 days after this date ensures the proper planting time to avoid not only problems from the Hessian fly, but also disease problems from barley yellow dwarf virus and several foliar diseases. Planting before these dates has lowered yield by 7 to 20% in research trials due to diseases and insect problems.

Weather Outlook

Authors: Jim Noel

After a dry week last week, it will become wetter this week.
The next week will see temperatures almost 10 degrees above normal with normal near 70 degrees F and 50 degrees F +/- 5 degrees depending on your location in the state. Precipitation will be above average during the next week also.
The week of Sept 28 - Oct. 4 will see temperatures return to near or slightly below normal and more normal rainfall. Overall, temperatures and rain will be close to normal the next 2-3 weeks.
There is a 90-100% chance of 1" of rainfall the next 2 weeks.
There is a 50-80% chance of 2" of rainfall the next 2 weeks.

Herbicide Resistance Meetings in Southwest Ohio

Authors: Mark Loux

In cooperation with industry, we have put together two brief meetings on herbicide resistance that will take place this Friday, September 25. The purpose of the meetings is to review the management of glyphosate-resistant marestail and giant ragweed. An overall goal is to help ensure that growers and agronomist are up to date on the programs needed to adequately control marestail and giant ragweed, and where new herbicides and fall and spring residual herbicide applications fit in these programs. The meetings consist of a presentation by Mark Loux, followed by a question and answer/discussion period.
The morning program, from 9 to 11 am, will be held at the Elk’s Club in Wilmington, at 2541 Rombach Avenue. Coffee and donuts will be available. The afternoon program, from noon to 2 pm including lunch, will be held at the Best Western Inn in Mount Orab, at 100 Leininger Street. There is no cost, but please RSVP by Wednesday to Chris Weed, chris.weed@syngenta.com, or 513-932-2759, so we have a head count for food.

Archive Issue Contributors: 

State Specialists: Anne Dorrance (Plant Pathology), Ron Hammond, Andy Michel, and Bruce Eisley (Entomology), Peter Thomison (Extension Corn Specialist), Mark Loux (Extension Weed Specialist), James Noel (NOAA/NWS/OHRFC). Extension Educators and Associates: Glen Arnold (Putnam), Roger Bender (Shelby), Mike Gastier (Huron), Wesley Haun (Logan), Harold Watters (Champaign), Greg LaBarge (Fulton), Les Ober (Geauga), Tim Fine (Miami), Bruce Clevenger (Defiance).

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.