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Ohio State University Extension


C.O.R.N. Newsletter 2008-21

Dates Covered: 
July 7, 2008 - July 15, 2008
Howard J. Siegrist

What to Look For and Prepare to Manage in Soybeans

Authors: Anne Dorrance

The wet and slightly warmer weather has gotten the diseases rolling. Now is the time to scout and prepare management plans.

1. Sclerotinia stem rot or white mold. This has been absent for the past few years due to the hotter, drier seasons. We do have some fields in the state that when weather conditions are conducive (cool and wet prior to and during flowering) we have seen substantial losses. For those fields where Sclerotinia is an every-year thing, this is the time to make plans for treatment. Thiophanate methyl (Topsin M) is the only fungicide labeled for control of Sclerotinia stem rot. Applications should be made at the R2 growth stage not at R3.

2. Phytophthora stem rot is also showing up early. Primarily due to the heavy rains the previous two weeks. The classic symptoms are plants, scattered throughout the wet areas with the chocolate brown canker moving up the plant. The upper part of the plant will turn yellow and wilt. Stem rot only develops on plants that have a non-effective Rps gene or low partial resistance. Plants with scores in the performance trial of 5 or less never develop stem rot in the field. Not all companies use the same scale, so read the fine print, in the Ohio Performance Trial – 10 is dead – it’s not great.

3. Between R1 and R2 is the time to assess levels of brown spot and determine if frogeye leaf spot is present in the fields. Possibly due to the cold temperatures, brown spot has been slow to develop this year, which is surprising with the amount of rain. Frogeye should begin to show up in those fields where susceptible varieties are grown AND where inoculum from previous seasons exists. We should be getting to the point where frogeye is on the decline if we are using good rotations and planting lines with higher levels of resistance. If frogeye is present, 1 to 3 frogeye lesions at R1 in a 100 sq ft., sprays at R3 can result in greater than 10 bu/A yield savings.

July 2008 Weather Report

Authors: Jim Noel

Past Week: Near normal rain fell in most areas but heavy rains did fall mainly in northwest and southeast Ohio. Isolated 2-4 inch rains fell in the northwest.

Week 1:
An up and down week is expected. Hot and humid early week with storms followed by cooler and drier weather for the second half of the week.

Week 2: More storms early next week with more ups and downs in the temps.

Week 3: More swings in temperatures from above to below with scattered storms.

Overall: the rest of July will be near to slightly above average temperatures and near to slightly above normal rainfall most areas. Temperatures and rainfall will swing from hot and humid with storms to cooler and drier about every 2-4 days for the foreseeable future.

August is likely to be near to warmer than average with near average rainfall at this time.

Fertilizer Prices Continue Higher

Authors: Barry Ward, Brian Freytag

Retail fertilizer prices in Ohio continue to surge as a combination of strong world demand, supply shortages, supply disruptions, high energy/transportation costs and a weak U.S. dollar make for a bad combination for farmers looking to make purchases.

Retail fertilizer price surveys show anhydrous ammonia prices to be 16% higher than they were in mid-March. Anhydrous Ammonia prices averaged $910 per ton on July 2nd compared to $782 per ton on March 26th. Retail UAN (28%) averaged $425/ton on July 2nd while UAN (28%) shipped direct to farm storage averaged $402/ton. Urea prices are significantly higher (36%), averaging $705/ton on July 2nd compared to $520/ton on March 26th.

Phosphorous fertilizers prices continue to hit new records as MAP and DAP both are averaging over $1000 per ton. As of July 2nd our survey showed MAP averaging $1092/ton and DAP averaging $1195/ton. This compares to the March 26th spot prices of $914/ton for MAP and $917/ton for DAP.

Potash is also experiencing big run-ups in price as the average price on July 2nd was $686/ton. This is a 24% increase over the March 26th price of $557/ton.

Prices as of 6/17/08
Cost per lb. of actual N:
Anhydrous Ammonia: $910/ton = $0.555/lb. of N
UAN (28%): $425/ton = $0.759/lb. of N
UAN (28%) Direct: $402/ton = $0.718/lb. of N
Urea: $705/ton = $0.766/lb. of N

Cost per lb. of actual P2O5 (value of N not considered for this illustration):
MAP (11-52-0): $1092/ton = $1.05/lb. of P2O5
DAP (18-46-0): $1195/ton = $1.15/lb. of P2O5

Cost per lb. of actual K2O:
Potash (0-0-60): $686/ton = $0.572/lb. of K2O

Cereal Leaf Beetle on Corn

Authors: Bruce Eisley, Andy Michel, Ron Hammond

We received a number of reports last week of adult cereal leaf beetles (CLB) feeding on corn leaves. These adults emerged from wheat and other cereal grain fields where their larvae were in high numbers. Because most of those fields are mature and nearing harvest, the adults have moved to “greener pastures”, which in Ohio is often nearby corn fields.

The adult insects will feed for 2-3 weeks before going into diapause. So far most of the feeding, based on reports, is on the edges of corn fields nearest the wheat or other cereal grain crop. According to the information we have available, the feeding should not be a problem unless it becomes extremely heavy, over 50% defoliation, with a lot of adult CLBs present, and with corn under stress. The latter is especially important when drought is occurring, although the cold and wet conditions might also be putting the corn under stress.

If a decision is made to treat, consider only treating the edges of the field if that is where the feeding is occurring. Although this is somewhat of a new problem, we would expect to see it more in the future if cereal leaf beetle continues to be a problem in wheat and the other cereal grain crops. If you have read this C.O.R.N. newsletter the past few years, you will know that CLB problems are becoming more frequent. If that trend continues, we would also expect more of this early-season adult CLB feeding on corn in the future.

Leaf Webbing Insects Found on Soybeans

Authors: Bruce Eisley, Andy Michel, Ron Hammond

This past week we had two insects brought into us by Ron Becker, Wayne County Extension, that were found in local soybean fields. Both are insects that web leaves together to form a “protective home” where they spend most of their time.
The first is a relatively common insect to soybean in the Midwest, although usually not found every year, the thistle caterpillar . This caterpillar is the larva of the painted lady butterfly, a common butterfly usually associated with thistles, which migrates into the Midwest from southwest locations. Although seldom reaching economic levels, it has been known to cause losses on newly emerged soybean.

The second insect that was brought in is rare in Ohio soybeans, although Dr. Chris Difonzo at Michigan State says that she has found these off and on over the years in her state. The insect is the silver spotted skipper, whose larva is a rather bizarre looking creature (see a picture of this insect at . Although more common in the eastern U.S. around Delaware and Maryland, this was the first time that we have seen it spread throughout a soybean field in Ohio (at least to our knowledge). While not at economic levels, their presence caught our attention.

Both these insects can be found by finding leaves that appear webbed together, and then slowly opening the leaves to reveal which insect is present.

Determination of Kernel Numbers in Corn

Authors: Peter Thomison

Last week corn “exploded” in growth across much of Ohio. However, there is considerable variability in corn growth and development - with much of the early corn (planted in April/early May) at or beyond V14 to V15 (14 -15 leaf collar stage), and corn planted in early to mid-June at V5 to V6 or later.

As early as the V4/V5 stage, ear shoot initiation is completed and the tassel is initiated on the top of the growing point. During the rapid phase of corn vegetative growth, now evident in the early planted corn, ear yield components are being determined.

Kernel row numbers per ear are generally established by about V12 (the 12 leaf collar stage). Kernel row numbers are usually less affected by environmental conditions than by genetic background. Corn hybrids characterized by "girthy" ears exhibit more kernel rows (about 18 or 20 rows) than hybrids with long tapering ears (about 14 or 16 rows).

Determination of kernels per row (ear length) is usually complete about one week before silking (R1) or about the V17 stage. Unlike kernel rows per ear, kernels per row can be strongly influenced by environmental conditions, so the absence of stress conditions, such as drought, this year bodes well with regard to the potential number of kernels on developing ears.

2008 Field Day and Events Schedule Website

Authors: Alan Sundermeier

The following link will have the 2008 Field Day and Events Schedule that have both Free Events and Events with Cost or Registration that are Open to the Public. Each listing will have the event name, date, time, location, web link, and more.


Archive Issue Contributors: 

Contributors: Pierce Paul, Anne Dorrance, and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel, and Bruce Eisley (Entomology), Peter Thomison (Corn Production), Jim Noel (NOAA). Extension Agents and Associates: Harold Watters (Champaign), Jonah T. Johnson (Clark), Marissa Mullett (Coshocton), Steve Foster (Darke), Bruce Clevenger (Defiance), Les Ober (Geauga), Gary Wilson (Hancock), Howard Siegrist (Licking), Todd Mangen (Mercer), Tim Fine (Miami) Suzanne Mills-Wasniak (Montgomery), Glen Arnold (Putnam), Mark Koenig (Sandusky), and Roger Bender (Shelby).

Crop Observation and Recommendation Network

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.