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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2010-16

Dates Covered: 
June 8, 2010 - June 15, 2010
Jon Rausch

Late corn and soybean plantings

Due to persistent rains and wet soil conditions, we’ve received questions about the advisability of planting corn vs. soybean after mid-June in NW Ohio. These questions have arisen in part because some corn fields need to be replanted due to emergence problems, including soil crusting, possible herbicide injury, hail, ponding, and saturated soil conditions.

Corn is not recommended as a late crop after mid June. Soybean is an option until early July. Some exceptions to late plantings of corn might be if corn is being grown for silage rather than grain, and N and corn herbicides had already been applied..

Recent studies have shown that good yields are possible with corn planted as late as mid-June but as a rule there’s likely to be greater yield variability with late planted corn than late planted soybean. Moreover, given current corn and soybean prices and production budgets planting soybean is going to be more profitable in most situations.

We can lose as much as 50% or more of our yield potential when corn is planted in late June (Ohio Agronomy Guide online at We lose about 1 to 2 bu/A of yield  with every day of delayed planting after the first week of May  - with the yield loss increasing more, the later it gets. There is an increasing risk of the corn crop not maturing before frost  - unless growers plant hybrids of considerably earlier maturity than those normally planted.

Yields of soybean planted in late June are typically 65 to 75% of normal. Effects of soybean relative maturity on grain yield can be large for late plantings. A key consideration in late soybean plantings is planting the latest-maturing variety that will reach physiological maturity before the first killing frost. Generally, stay with the same planned maturity (unless it is earlier than 3.0). Keep in mind that a 3.5, 3.7, and 3.9 may be used until July 1 for northern, central, and southern Ohio, respectively. Planting rate should be increased to 200,000 – 225,000 seeds/A and established in narrow rows (6 – 7.5 inch). If planting is delayed past June 15, a desired seeding rate may be 225,000 to 250,000 in narrow rows.

Weather conditions, especially adequate soil moisture, often limit the yield potential of late planted both corn and soybeans. However, corn is highly susceptible to drought damage during pollination and early grain fill and the potential for high temperature and water stress typically increases later in the growing season when late planted corn flowers. Because soybeans flower over a longer period, they’re usually less vulnerable to this type of injury. As a result, late planted corn is a riskier crop than soybean. Some other factors to consider with late planted corn include:

  • Higher corn grain moisture requiring artificial drying that will increase cost of production
  • Lower test weights that may result in significant dockage (especially if a frost occurs before black layer)
  • Greater stalk lodging and stalk rots. Late crops may experience more stress during grain fill and weathering during dry-down
  • Increased injury from silk clipping insects like corn rootworm beetles and Japanese beetles (and second generation European corn borer damage, if the hybrids planted are not ECB Bt hybrids).  
  • Greater foliar diseases injury. Losses to gray leaf spot may increase with later planting dates.
  • Less effective N uptake. If conditions turn dry after planting, late sidedress N applications may be ineffective.

Hail injury to corn should be limited

Some of the severe thunderstorms over the weekend were accompanied by hail that may have caused damage to crops.  In corn, the impact of hail damage is largely dependent on the crop's stage of development.  Hail affects yield primarily by reducing stands and defoliating plants. Most of the hail damage results from defoliation. Generally, the corn plant is little affected by hail prior to the 6 to 7 leaf stage because the growing point is at or below the soil surface and in the leaf whorl. However, once the growing point is elevated above the soil surface due to internode elongation, the plant grows rapidly and becomes increasingly vulnerable to hail damage with the tassel stage/pollen shedding stage (VT) being the most critical period.

Severe hail damage prior to the 6 to 7-leaf stage can also result in “twisted” or “tied” leaf whorls as injured plants recover and new leaves try to unroll. The twisted and tied leaf whorl occurs because damaged whorl leaf tissue dies and restricts expansion of unaffected whorl leaves.  However, most plants will grow out of this problem and tied whorls seldom cause major yield loss. Moreover, bruising from hail early in the season usually does not result in increased stalk lodging or stalk rot later in the season.  Results of an Ohio study that evaluated recovery of hail damaged corn in fields exhibiting severe twisted and tied leaf whorls are available online at

Leaf damage by hail usually looks much worse than it really is, especially during the early stages of vegetative growth. Shredded leaves still have some capacity to contribute to plant growth. Plants not killed outright by hail usually show new growth within 3 to 5 days after injury occurs (i.e. if damage occurs prior to tasseling). For this reason, estimates of hail damage should be delayed several days to allow for this period of re-growth. If rains associated with hail damage splash bacteria into hail damaged leaf whorls, bacterial soft rots may develop and destroy the corn growing point; this problem is more likely when ponding or standing water occurs after the storm.

The hail insurance adjustor's growth staging system counts leaves beyond the last visible collar to the uppermost leaf that is 40-50% exposed whose tip points downward - usually this results in a leaf stage that is numerically 2 leaves greater than the "leaf collar method" (e.g. a V6 plant according to the leaf collar method would probably correspond to a 8-leaf plant according to the hail adjustor's method).

How do we estimate the potential yield loss from recent hail storms? Corn growth stages in Ohio vary considerably depending on location, planting date, etc. Most corn in NW Ohio has not progressed much beyond the V6-7 stage (as of 6-8-2010). Based on estimates of the National Crop Insurance Association (see table below), at the 8-leaf  stage (or about V6)  if 50% of the leaf tissue is destroyed by hail, a corn plant loses only 3% of its yield potential; if 100% defoliation occurs, a corn plant loses 11% of its yield potential. Since the growing point of most corn is at or below the soil surface, we can probably expect limited yield loss from recent hail damage.

Percent yield loss in corn based on growth stage & defoliation

(adapted from NCIA Corn Loss Instructions, rev. 1984)


Percent Leaf Defoliation

Growth Stage*

























*as determined using the hail adjustor’s leaf staging method


For more information on evaluating hail injury in corn, consult

Mangen, T. and P. Thomison, 2002. Early season hail damage in corn: effects of stalk bruising and tied whorls. Agronomic Crops Team On-Farm Research Projects 2000. Special Circular 179-01. Available at

Nielsen, RL (Bob). 2008. Recovery from Hail Damage to Young Corn

Corny News Network, Purdue Univ. [On-Line]. Available at

Wheat is Already Turning in Ohio

It is only the first week of June and the wheat is already turning in some fields in Ohio, leaving some producers concerned that this will greatly affect the overall yield of this year’s crop. In general, the 2010 wheat crop is about 7 to 10 day ahead of schedule, with flowering occurring earlier than usual this year. With the 4 to 5 consecutive days last week with daytime temperatures above 80 F (and above 90 F in some cases) and relatively high nighttime temperatures, the wheat is beginning to lose its green color in some fields, taking on a straw color, typical of maturing wheat. Warm late-spring – early-summer weather conditions usually shorten the grain fill period of the crop in Ohio, leading to smaller kernels and lower overall yield. This is because once the wheat starts to lose its green color, the amount of sugars produced by the leaves and spikes and transported to fill grain is greatly reduced. However, the wheat is only just beginning to turn and there is still a considerable amount of green plant tissue in those early fields. Although the few cool nights in the forecast for the next few days will not bring back the green color, this will slow down the maturation process, allowing grain fill to continue for a bit longer.

Insect Update

Although things are generally quiet on the insect side, there are some isolated problems in the state. Slugs continue to cause more problems on both corn and soybean than seen in the past few years, with calls coming in from not only Ohio but from neighboring states. We have had calls on various cutworm problems, including some that suggest perhaps another cutworm is active. We would remind growers that for proper identification of cutworms or for that matter, any insect, we need to see the actual insect or have a very good picture of it sent to us. Many times pictures that are sent to us are not clear enough for proper identification. Thus, it is best to use a digital camera when sending us photos unless your cell phone can take good pictures.

Planning for Western Bean Cutworm for 2010

Early June is the time to begin planning for monitoring of western bean cutworm.  Western bean cutworm is a corn ear pest that begins adult flight in June, with peak flight occurring usually in late July.  Eggs are laid during July and August, and, after egg hatch, larvae feed on tassels (if corn is in pretassel stage), silk and on the kernels.  Monitoring for adults provides an indication if western bean cutworm is in your area and helps determine when egg scouting should begin.  Perhaps the easiest way to monitor for western bean cutworm adults is using an empty milk jug with openings cut on the 4 sides, and a pheromone lure attached by a paper clip at the top (see our fact sheet at: and the NC-IPM pest alert:  Lures can be purchased at Great Lakes IPM (, 1-800-235-0285). An individual lure lasts 3-4 weeks.  The bottom reservoir is filled with 4 parts water, 1 part antifreeze with a drop of dish soap.  The trap should be placed on the edge of a cornfield before July 1 and inspected at least every week, but more often once adults are caught.  Western bean cutworm adults can be identified by a white strip on the leading edge of the forewing, white and brown circle in the middle of the wing, and a brown or kidney or comma shape behind the circle.  The general recommendation is that egg scouting should begin when moths are caught on consecutive nights. 

Remember, this pest first found in Ohio in 2006.  Since then, numbers of adults caught has increased to 566 in 2009 (Ohio maps can be found at Damage has been seen in nearby Indiana, Michigan as well as Ontario, Canada.  However, we have not found damage or egg masses, and have only found 1 larva in Putnam County to date.  OSU Extension will again be trapping across Ohio, and collaborating with surrounding states and Canada.  Ohio maps will be placed on our website below as soon as moth catch begins. Check the C.O.R.N. newsletter during the course of the season for updates on trap counts, scouting and management.   

Stagonospora and Loose Smut in Some Ohio Wheat Fields Fungus on wheat head

Stagonospora and Loose Smut in Some Ohio Wheat Fields

Rain and warm weather is causing Stagonospora to show up in some fields across the state. Wheat is just past pollination (at early to mid grain fill) in central and northern Ohio and the disease is already on the leaf below the flag leaf in some field planted with susceptible varieties. Under warm, rainy conditions, this disease can quickly spread to the flag leaf and the head, and if this occurs before grain fill is complete, both yield and quality losses may occur. The disease first appears as dark brown flecks or spots on the lower leaves, occasionally with a yellow halo, progresses up the plant and becomes oval and light brown with dark centers. As the lesions enlarge the centers turn grayish-white. If severe blighting of the upper leaves occur before soft dough, the grain will be lightweight and shriveled.

Several fungicides can be used to manage Stagonospora. For those fields planted with susceptible varieties, with disease already on the flag leaf or the leaf below the flag leaf, some producers may be considering applying a fungicide to minimize yield and quality loss. However, before using a fungicide, read labels carefully and check disease levels in your field. For most of the effective products, the pre-harvest interval is between 30 to 45 days, and in some cases, these products cannot be applied after head emergence (Feekes 10.5). We are already in early June and with warmer weather in the forecast for early summer, wheat has already started turning or will start turning and maturing in the next few weeks in Southern Ohio and towards the end of June in Central and Northern Ohio. Harvest will begin between late-June and early-July, in less than 30-45 days. As a result, most fungicides are already off label or will be off-label within the next few weeks. For more on fungicides go to:

Another disease that has been reported in some fields is loose smut. It shows up as black spore masses in place of the kernels, and as the spores are blown away by wind, the bare rachis remains on the heads. This disease is generally not a problem in Ohio because most of our wheat seeds are treated with a fungicide. However, when untreated, poorly treated or bin-run seeds are planted, loose smut incidence may be high, leading to significant yield reduction. The smut fungus colonizes the embryo of the seed following infection of the floret during flowering and remains dormant in the seed from one growing season to another. Infected kernels may appear wholesome, but if used as seeds for the next season, will carry the disease to the new crop. As a result, avoid using seeds from smut-infect fields for planting. If these seeds are used, they should be treated with an effective systemic fungicide. Remember, read labels carefully before using a fungicide. For more on seed treatment go to:

Fungicides already being reserved for the 2010 Crop

Because of cool, wet conditions between late-April and the third week of May, Ohio’s corn and soybean are only just out of the ground in some fields and not even out of the ground in others. However, both corn and soybean producers are contemplating adding fungicides to their management programs for this year’s crop.      

Here is the data: Results from replicated fungicide trials conducted between 2006 and 2009 show very similar trends in terms of yield response across Ohio and across the Corn Belt. Corn hybrid yield response to foliar fungicides continues to be highly variable and unpredictable. Corn fungicide trials were conducted at four locations in Ohio (Western Research Station, near South Charleston; the Northwest Research Station, near Hoytville; the Snyder Farm, Wooster, and the ATI Research Farm in Apple Creek), providing a total of 25 trials for disease and yield comparisons. At each location, multiple hybrids with different levels of resistance to gray leaf spot and yield potential were planted, allowing for the evaluation of hybrid corn yield response to fungicides for a combination disease pressure, weather, and hybrid scenarios. Most of the trials were planted no-till or reduced-till into fields previously planted with corn.

In all cases, foliar fungicides were applied between tassel and silk emergence (VT – R1) at label-recommended rates at 20 GPA, using a high-clearance spray. At the time of fungicide application, only trace amounts of foliar disease were observed on the lower leaves (well below the recommended fungicide application threshold), and disease levels remained low through the growing season at all locations. Yields in the untreated checks ranged from 73.6 to 177.96 bu/A, with an average of 109.8 bu/A, whereas in fungicide-treated plots, yields ranged from 68.19 to 188.49 bu/A, with an average of 109.55 bu/A. Yield differences between treated and untreated plots (treated minus untreated) ranged from -16.70 to 10.53 bu/A, with an average difference of -0.28 bu/A. Similar fungicide trials were conducted by university researchers across the Corn Belt, with similar results. Depending on the fungicide, average yield differences between treated and non-treated were between -1.2 and 4 bu/A when foliar disease severity was less than 5% and between 1.6 and 10 bu/A when severity was greater than 5%.

Fungicide use remains most profitable when disease levels are high on a susceptible. Scout fields for disease before applying a fungicide. In addition to not always being profitable, the unnecessary use fungicides increase the risk of fungicide resistance, so when disease does occur these tools may not be effective. Monitor weather conditions to see if they are favorable for disease development. For gray leaf spot these are wet humid conditions during July and August. For northern corn leaf blight, these are cool, wet conditions. Drought conditions do not favor either disease. 

Modified Relay Intercropping of Soybeans into Wheat Field Day, June 23MRI fieldday map

Modified Relay Intercropping of Soybeans into Wheat Field Day, June 23

Wheat has been interseeded with soybeans in north central Ohio last week. Wheat is a flexible, adaptable plant with a growing season that starts with planting in the fall and ends with harvest in the early summer. This adaptability allows farmers to capture some 66% of the traditional growing season — May 20 to September 30 — to produce a second crop through the interplanting of soybeans into wheat in late May or early June. This practice is known as Modified Relay Intercropping (MRI).

In the MRI system, two crops — wheat and soybeans — are harvested in the same year. However, because of the difference in crop growth requirements and grain markets, farmers can effectively hedge production and price risk in an MRI system in most years. Producers considering using an MRI system should plan to grow wheat in such a manner (wheat rows 15 inches or less in width) that yield is not significantly reduced from wheat grown in a conventional system.

Long-term research at The Ohio State University's Ohio Agricultural Research and Development Center, in Crawford County and locations in Indiana has shown that MRI or Relay Intercropped wheat will yield about 90 percent of conventional wheat.

Soybean production in an MRI system is more speculative than wheat production due to the need for adequate rainfall in July and August. Thus, MRI should only be done on soil types with good water holding capacity.

Different wheat row spacing has been used successfully in MRI. Wheat is a very adaptable plant and will compensate for different row spacing by tillering. Wheat row spacing may range from two rows of wheat planted about 6 inches apart (with a 14 inch open space for soybean planting) to even row spacing of 10 to 15 inches.  Wheat must be planted to accommodate soybean planting equipment. A tram line is essential to this system to allow for the tractor and planter or drill to run through the wheat with minimal damage.  Row spreaders are also needed on the tractor and drill to move plants out of the row middle when interseeding. Other wheat row spacing configuration is possible; however, production factors such as soybean planting date and weed control programs will need to be considered.

For a more thorough overview of this system go to the following pages for more information; and

A MRI field day is scheduled for June 23 at 7:00 PM at the Rich Smith Farm location near Willard, Ohio.  For more information call Crawford County 419-562-8731. See also the website for more information:




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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.