CFAES Give Today
Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2011-30

Dates Covered: 
September 6, 2011 - September 13, 2011
Justin Petrosino

September 2011 Weather Update

The remnants of tropical storm Lee will play havoc with early September weather in the Ohio Valley this week. Weather models did not capture this system well even into this weekend. Therefore, the outlook has changed this week due to Lee.

The week of September 5-11 will feature below normal temperatures and above normal rainfall. Rainfall will likely range from 0.75 to 2.00 inches with isolated totals possibly reaching 3 inches in the north or west due to Lee. High temperatures will start the week mostly in the 60s and climb into the 70s by the weekend. Lows will mostly be in the 50s.

The week of September 12-18 will return to more typical fall weather with temperatures slightly warmer than normal and rainfall at or slightly below normal. Normal rainfall is about 0.5 to 0.75 inches per week. However, it should be noted that in autumn we often increase our spread between highs and lows. There will be some days next week where the north will start the day in the 40s and still reach 70s for highs.

Looking farther ahead for the rest of September, temperatures will average above normal with normal rainfall. It appears the drier summer weather has ended so normal rainfall is the most likely outcome for later September.

Assessing the Risk of Frost Injury to Late Maturing Corn

According to the National Agricultural Statistics Service ( as of September 4th, 85 percent of Ohio’s corn acreage was in the dough stage (R4), which was 7 percent behind the five-year average. Thirty-seven percent of the corn acreage was in the dent stage (R5), compared to 64 percent for the five-year average. This later than normal maturation of the corn crop had led to questions about the likelihood for frost damage and whether more fuel will be needed to dry corn. 

In Ohio, physiological maturity (when kernels have obtained maximum dry weight and black layer has formed) typically occurs about 65 days after silking. At physiological maturity (kernel moisture approximately 30-35%), frosts have little or no effect on the yield potential of the corn crop. 

Dr. Bob Nielsen at Purdue University has summarized research findings from Indiana and Ohio that provide insight into both the calendar  days and thermal time (growing degree days, GDDs)  typically required for grain at various stages of development to achieve physiological maturity (kernel black layer, R6). This research was conducted at two locations in Indiana (west central and southeast) and two locations in Ohio (northwest and southwest) with three hybrids representing 97, 105, and 111 "day" relative maturities planted in early May, late May, and early June. The calendar days and thermal time from silking to black layer for the 111-day hybrid maturity are shown in Table 1 (from

 According to Dr.Nielsen, while slightly different responses among the four locations of the trial existed, there did not seem to be a consistent north / south relationship. Therefore, growers can use the results summarized in the following table to "guesstimate" the number of calendar days or heat units necessary for a late-planted field at a given grain fill stage to mature safely prior to that killing fall freeze. 

Table 1. calendar days and GDDs to black layer from grain fill stages R1-R5 for an adapted 111 "day" corn hybrid with GDD rating of 2760 GDDs from planting to black layer. Data averaged over eight trial sites.

Calendar days to kernel black layer (R6) from…

Planting date






Early May






Late May













GDDs to kernel Black layer (R6) from…

Planting date






Early May






Late May












Adopted from Brown (1999)


R1 = Fresh silks; R2 = Blister, R3 = White kernels w/milky fluid; R4 = Dough, no visible denting; R5 = late dent, all kernels visibly dented

How many GDDs can be expected from now until an average date of a killing frost for an adapted 111 day hybrid planted in mid June?  To answer this question, estimate the expected GDD accumulation from Sept. 9 until the average frost date (50% probability) for different regions of the state (Table 2). These GDD expectations are based on 30-year historical normals reported by the Ohio Agricultural Statistics Service. The GDD accumulation was calculated using the 86/50 cutoff, base 50 method.
If you want to determine the "youngest stage of corn development" that can safely reach black layer before the average frost date at a given weather station, use the information in Table 2 on remaining GDD in conjunction with Table 1 which indicates GDDs needed to reach black layer at various stages of grain fill. Compare "GDDs remaining" for the site with the GDD required to achieve black layer depending on the corn's developmental stage.
Table 2. Estimated GDDs remaining from Sept. 9 to the first fall frost for Ohio.



Median Frost Date

(50% probability)

Estimated GDDs Remaining

From Sept. 9 to Fall Frost





Oct 10 – Oct 20

300 – 350

North Central

Oct 10 – Oct 25

290 – 375


Sept 30 – Oct 25

240 – 386

West Central

Oct 10 – Oct 15

328 – 385


Oct 5 – Oct 15

339 – 400

East Central

Sept 30 – Oct 15

260 – 378


Oct 10 – Oct 15

349 – 412

South Central

Oct 15 – Oct 20

426 – 478


Oct 5 – Oct 15

330 - 390

If your corn is in the dent stage (R5) as of Sept. 9, will it be safe from frost? Table 1 indicates that corn planted in mid June required about 217 GDDs to reach black layer from R5 and Table 2 indicates that all regions of the state are likely to accumulate sufficient GDDs before the 50% frost date. 
However, if your corn is in the “dough” stage (R4) as of Sept. 9, it might be a different story. The kernel development - GDD accumulation relationships in Table 1 indicate that corn planted in mid June that is at R4 needs about 489 GDD to reach black layer. Table 2 indicates that only one region of the state (south central Ohio) comes close to accumulating that number of GDDs before the 50% frost date. 
The research results in Table 1 demonstrate that late planted corn has the ability to adjust its maturity requirements, and most of this adjustment occurs during the late kernel development stages. In previous growing seasons when GDD accumulation was markedly less than normal, the corn crop has usually achieved physiological maturity before the first frost occurred. 
Nielsen, R.L. 2011. Predicting Corn Grain Maturity Dates for Delayed Plantings
 Corny News Network, Purdue Univ. [On-Line]. Available at 
Watch Pre-Harvest Intervals if Spraying for Soybean Aphid

Watch Pre-Harvest Intervals if Spraying for Soybean Aphid

We have heard of soybean fields with pesky soybean aphids that are persisting on late-planted beans, especially in double crop fields.  While the cool weather is likely to slow down the population growth rate of soybean aphid, there may be fields that can still reach the economic threshold of 250 aphids/plant before growth stage R6 is reached (at growth stages R6 and above, soybean aphid thresholds can be increased).  Growers are urged to continue to check soybean fields as we head into the later weeks of September, and check for increasing soybean aphid populations.  

However, the later that control applications are made, the more important pre-harvest intervals become.  The pre-harvest interval is the time between application and when harvest can begin.  For soybean aphid control this interval ranges from 18 to 45 days depending on the product used.  See the full list of available insecticides and their pre-harvest intervals in bulletin 545 at   

Plan to attend the Farm Science Review September 20, 21 & 22

The growing season started late for us in 2011, but the crew and the grounds are ready for Ohio State University’s annual fall farm show at their site on the grounds of the Molly Caren Ag Center at the intersection of US 40 and SR 38 just north of London. Crops look very good and as of today harvest demonstrations are planned – yield expectations are average, but average this year is better than we expected.

Tickets are available now for the 2011 Farm Science Review – to be held on September 20, 21 and 22 in London Ohio – All Extension offices in Ohio and many agricultural businesses have the tickets for sale at $5 each. Tickets at the gate are $8.

Agronomic Crops Team at the Review

We have added a number of field demonstration plots to the Farm Science Review exhibit area for this year. We will again have the “antique corn” plots and will also have discussion plots on managing corn and soybeans for higher yield. We have education plots on cover crops and “bio-energy” crops, too. We think it is time to at least think about adding another agronomic crop to your enterprise – and that may be an energy crop. Stop by and get a tour from an Agronomic Crops Team member as you make your way from the parking lot to the exhibit area.

This year several Purdue Extension educators will also be working with us in the plots. Ask them and us how to win a free Purdue “Corn & Soybean Field Guide” or an Ohio State “Corn, Soybean, Wheat and Alfalfa Field Guide”.

In the spring of 2010 the Agronomic Crops Team developed a new website ( and updated the C.O.R.N. newsletter, stop by to share your comments and subscribe if you are not already a user.

Golf Cart Use

Golf cart, electric scooter, segway or approved disabled unit will be the only mode of transportation allowed for the 2011 FSR visitor.

As the Farm Science is a pedestrian show, it is important to limit the use of golf cars to those individuals who require this type of vehicle to use at the show. An expressed need for the use of a special need vehicle should be apparent, whether the vehicle is rented or brought by the individual. It is also the policy of the Farm Science Review to limit all vehicular traffic inside the exhibit area to a minimum and to maintain the area as a primary pedestrian facility. 

The use of a motorized vehicle is a privilege provided to the user.  The abuse of this privilege will result in the revoking of the issued Special Needs Vehicle Permit and the removal from the grounds of the Molly Caren Ag Center of the vehicle and the individual(s) to whom the Permit was issued. For more information on cart use see the FSR special needs policy:

•    Plan ahead to see your top priorities

Schedule of Events:

2011 FSR CCA College

The OSU Extension Agronomic Crops Team will again this year offer the FSR CCA College so that those CCAs working or attending the Farm Science Review can earn continuing education credits. This year the FSR CCA College is a little different and will not be on just one day, but all three days of the Farm Science Review is a CCA College. There are several CEU opportunities all over the grounds and all three days – September 20, 21 & 22:

·      At the Gwynne Conservation area will be Soil & Water CEUs

·      We’ll have Nutrient Management and Crop Production CEUs at the Small Farm tent

·      Pest Management CEUs at the Chemical Load Rinse Pad site

·      At the Agronomy Plots between the East End of the Exhibit Area and the public parking is this years largest display of Crop Production, Nutrient Management and Pest Management demonstration plots – all available for CEUs

o   Agronomic Crops state specialists and county field specialists will be on hand to discuss this year’s problems and talk about opportunities for the future for crop yield increases – for crop consultants and for growers

Watch for the “Are You Good Enough to be a CCA?” clipboards posted at each venue. On the clipboard will be a card reader, like those you have seen at the Conservation Tillage Conference. Slide your CCA or CPAg card through the reader during the event that offers CEUs and you’ll be credited that educational benefit.

See all the FSR CCA College opportunities on the Agronomic Crops Team website: You may also get more information on the program from Harold Watters at  Buy Farm Science Review tickets at your local County Extension office for $5 or at the gate for $8. For more information on the Farm Science Review:


Archive Issue Contributors: 
Archive Issue Authors: 

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.