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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2005-17

Dates Covered: 
June 14, 2005 - June 21, 2005
Greg La Barge

Soybean Rust and Tropical Storm Arlene

Authors: Anne Dorrance

Based on some phone calls, I understand the rumour mill is in full tilt. As of today (6/14), there are NO CONFIRMED cases of soybean rust in Kentucky, Tennessee, Alabama, Mississippi, Louisiana. The only confirmed cases are in Georgia (and this is very, very low infection) and Florida. Sprays are NOT RECOMMENDED for the near future.

The sentinel plots were all scouted last week, but only some Septoria brown spot was identified. In many of the plots that reported bean leaf beetle feeding, the new leaves have no feeding damage, indicating that we are nearing the end of this generation. What’s next. Some concern has been generated due to the arrival of tropical depression Arlene. Based on the computer models- they report that the most significant soybean rust spore movement and deposition would occur from Florida, Georgia South Carolina, Alabama, Mississippi, most of Tennessee and Kentucky and the southern half of Louisiana. Marginal areas would be extreme eastern Arkansas and Southeastern Missouri, lower Ohio Valley and central Appalachians. Looks like we in Ohio are off the hook for several reasons, no rains fell as part of this storm in many areas of the state and our soybeans are only at very early growth stages (V2-V4). Canopy closure has not occurred in the majority of fields across the state. From this storm – to determine if these predictions were correct, the sentinel plots will be scouted at the end of next week. It will take 7 to 10 days for the spores that landed to infect the leaves, produce lesions that will produce more spores. The key thing is that we do not know if this storm carried spores or if it did how many. As many of you recall from hurricane Ivan – while many southern areas identified soybean rust – those infections were quite diluted. We’ve got plenty of time.

Aphids on Early Soybean

Authors: Bruce Eisley, Ron Hammond

Last week, we found soybean aphid on soybeans on the Waterman Farm of OSU in the middle of Columbus, the first confirmed sighting of this pest in Ohio on soybeans. However, over the past 24 hours, we have received word of aphids occurring in a number of fields in northwest Ohio, often at levels of 20-30 per young plant. Although not all plants have these densities, enough plants were infested to cause grower concern this early in the season. What does this mean, and what should growers do? Obviously, we are beginning to see soybean aphid build up. Does this mean that the summer of 2005 will be another severe year for aphid? For no other reason, it means that we will need to be checking our fields closely.

In terms of these early population increases, we are still suggesting taking a wait and see approach to the need for treatment. There are still a number of predators out there that will help to keep these early populations in check for a while, or at least slow their population increases until soybean reproductive growth stages. These predators include lacewing larvae, syrphid fly larvae, minute pirate bugs, and a predator mite. All of these predators are very small, and are usually missed if looking for them. You will probably not see the multicolored Asian lady beetle at this time.

We still feel that the threshold for spraying should remain at 250 aphids per plant, beginning at growth stage R1 or the flowering stage, and continuing through pod fill. Observations from other states in years past suggest that treating during these early vegetative stages did not result in any yield savings. The other concern is spraying an insecticide this early, and what could then happen. Spraying now will not only kill a good proportion of the aphids, but also most of the natural predators. Afterwards, the remaining aphids or new colonizers that will come might build to larger populations in an “enemy-free space” later in the summer. A grower who treats with an insecticide now may be risking a need for a second insecticide treatment.

A major worry is that numerous fields will be sprayed shortly with Roundup, and many growers will consider adding an insecticide to “knock-down” the aphids that are present, using the spray as an insurance type of treatment. As mentioned above, this action could result in greater problems later in the summer. As an insurance or prophylactic treatment, we do NOT recommend this approach. Our best recommendation is to try and wait at least until flowering begins before taking action when the threshold of an average of 250 aphids per plant is reached. If you feel that the aphids have reached a level in these young, vegetative stage plants that require treatment, do so but keep a close watch on these fields for possible large buildups of aphids in later summer. Perhaps you could leave untreated check strips to see if the insecticide treatment did any good, basing it on what happens later this summer. An additional concern with this approach is the selection of insecticide. Pyrethroids tend to flare spider mite populations. Parts of Ohio are experiencing very dry and hot conditions, and we are already seeing some fields with early twospotted spider mite populations (see mite article in this newsletter). If deciding to spray under these conditions, Lorsban is perhaps the product of choice because it does do a good job on spider mites. But we do NOT recommend throwing in an insecticide with your Roundup just for insurance, just because you are already going over the field. This is not an appropriate IPM approach!

Risk to Delayed Weed Control in Small Soybeans

Authors: Mark Loux

The weed situation in our soybean research plots is similar to that in many fields around the state – soybeans are still small, but the weeds are large enough to justify herbicide application. We typically apply glyphosate in Roundup Ready soybeans when most of the annual weeds are 4 to 8 inches tall (with some giant ragweed plants larger). This often corresponds to soybean growth stage of 3rd or 4th trifoliate, but this year it is more likely to correspond to soybeans in the first to second trifoliate. Weed size should be the indicator for timing of postemergence herbicide treatments, not soybean size. A number of university studies have shown that soybean yields can be reduced if the weeds are allowed to exceed 6 to 8 inches in height before treatment with glyphosate. Applying glyphosate at the appropriate weed size could be even more important this year when soybeans are growing so slowly. Weeds will be more effectively controlled when they are small, which reduces the need for higher glyphosate rates and minimizes the risk of herbicide resistance (we think). A reminder on the economics of Roundup Ready soybeans – quite a bit of the weed control cost is incorporated in the price of the seed, while the glyphosate is inexpensive to apply. So, the most effective management of Roundup Ready soybeans is to apply glyphosate initially when the weeds are 4 to 8 inches tall, regardless of soybean size. Scout fields and make a second glyphosate application in several weeks if necessary to control later-emerging weeds.

Producers of non-GMO soybeans have little choice on the timing of application. Conventional postemergence herbicides should be applied before weeds exceed about 4 to 6 inches in height, depending upon the herbicide and weed species. Delaying application can result in inadequate control, along with reduced yield. So, the strategy in non-GMO soybeans is much the same as in Roundup Ready soybeans at this time – apply herbicides based on weed size, and make a second application as necessary. Unfortunately, a second application is likely to be more costly in non-GMO soybeans compared to Roundup Ready, and is less likely to “finish off” weeds that survive the initial postemergence treatment.

Tips for When to Begin Wheat Harvest

Authors: Jim Beuerlein

Wheat grain is about 30 percent moisture when it reaches physiological maturity and can be harvested efficiently and easily when the grain moisture is between 14 and 20 percent. Harvesting above 20 percent grain moisture increases kernel damage, and reduces storability, test weight and germination percentage. Delaying harvest past the time that grain reaches 14 percent moisture reduces yield about one-fourth bushel per acre per day, increases cutterbar loss, and decreases test weight each time the grain is wetted by rain or very heavy dew. Also, the risk of loss by bird and rodent feeding increases as does the potential loss due to fire, hail, high wind, and other weather factors. Yield, test weight, germination percent, grain quality, and harvest efficiency are greatest when the grain moisture is between 14 and 20 percent moisture at harvest. Within that range wheat grain moisture decreases about one percentage point per day with normal weather conditions.

Plan to complete harvest before the grain moisture drops below 14 percent. Assuming that ideal harvest conditions last for six days enables one to estimate the moisture level at which harvest must start. If the crop can be harvested in two days, harvest can be delayed until the grain reaches 16 percent moisture. For a crop that will require six or more days to harvest, threshing should start when the grain reaches 20 percent moisture.

Early June is the time to prepare the combine for wheat harvest. Check thoroughly for worn or broken parts that should be replaced and then lubricate according to the operators’ manual. Adjust cylinder speed, concave clearance, fan speed, and screens for wheat. Service the motor and remove any combustible material from the motor compartment to make the machine field ready so harvest can start on time and at the proper grain moisture content.

Mealybugs Found on Soybean-Do Not Confuse with Aphids

Authors: Ron Hammond, Bruce Eisley

We found a whitish-yellow insect on the underneath side of soybean leaves while checking soybeans for aphids this week in central Ohio. At first glance it appeared to be aphids, but on closer examination with a good hand lens, we discovered the insect is a mealybug. Mealybugs derive their name from the white, waxy, mealy secretions that cover their bodies. They attach a number of house plants and some plants in the field. They damage plants by sucking the juice from the leaves. They are in the same order as aphids but a different family.

The mealybugs we found, were whitish-yellow in color, very slow moving, flatter than aphids and of course did not have “tailpipes” that are commonly found on aphids. Many of the leaves sampled had multiple mealybugs on them The soybeans were no-tilled in April and the vegetation burned off. Later planted no-till soybeans in the area also had mealybugs on the leaves but in lesser numbers.

We do not know why the mealybugs were on the leaves or if they are doing any damage to the soybeans. The important thing at this time is to not confuse these mealybugs with aphids and this reinforces the importance of having a good hand lens when in the field and making sure of the proper identification of any insect that is found.

Twospotted Spider Mites on Soybeans

Authors: Ron Hammond, Bruce Eisley

If mealybugs and soybean aphids, two very small insects, were not enough to try to identify on soybeans, we found a field at the OARDC Western Station in Clark County that had a population of twospotted spider mites. The most likely reason for mites showing up this early is the hot and very dry weather that some areas of Ohio have been experiencing. If you have been following similar reports from other Midwestern states, you would know that Illinois is also experiencing populations because of the weather conditions. Knowing how to identify twospotted spider mites is important for a number of reasons. First, when looking for soybean aphids, you do not want to mistake other insects such as potato leafhopper nymphs, thrips, mealybugs, and now, spider mites, as aphids. Second, if hot and dry weather continues, the likelihood of a mite problem becomes greater. Spider mites infestations can be first noticed by yellow stippling on the upper surface of the leaves. Then, the mites themselves can be identified by examining the critters that will be on the underside of the leaves with a good hand lens, the same hand lens that every soybean grower should now have to help identify soybean aphids, mealybugs, mites, and even soybean rust. Please contact your local extension educator if you come across any of these problems so that we can determine the appropriate action to take.

Impact Of Hot Weather On Wheat Yields

Authors: Patrick Lipps, Jim Beuerlein

Wheat yields are generally greater during years with relatively cool temperatures during the grain filling period. This is one reason why some of the highest yields recorded in the U.S. are in the Pacific Northwest where the crop matures under 50 to 75 degree summer temperatures. In Ohio, wheat suffers from exposure to high temperatures during the grain filling period and in some years the high temperatures in June limit the number of days the grain fills by causing premature ripening of the crop. Generally, temperatures above about 85 degrees F are detrimental to wheat production.

In Ohio the grain filling period ranges from about 14 to 22 days and each day of grain fill adds about 4.5 bushels to the yield. When the weather is cool and there is little disease pressure the yield potential can be as high as about 6 bushels per acre per day of grain filling whereas during seasons with high disease pressure and high temperatures the potential can be reduced to about 3 bushels of grain per day of grain fill. Obviously the relationship between temperature, disease and potential yield more complicated that presented here complicated, but these are general trends. Although Ohio is now experiencing day time temperatures reaching into the 90 degree F range, there is very little disease affecting the wheat crop thought the state. If our experience is correct, then the effect of recent higher temperatures may not have a major effect on Ohio's wheat yields, although it will likely have some effect. Wheat in southern Ohio is now in its 19th to 21st day of grain filling and in most northern Ohio fields wheat has now had about 10 to 15 days of grain filling. Wheat in southern Ohio is showing signs of changing color so the end of the wheat season is drawing near in the south.

Wheat Disease Levels Remain Low

Authors: Patrick Lipps, Pierce Paul, Dennis Mills

The cooler weather in May limited the initial development of disease in most Ohio wheat fields and the recent dry conditions has kept disease levels quite low. In particular, leaf blotch diseases are at low levels as well as diseases usually found on the heads. This is great news for wheat producers. Secondly, the head scab risk predictions continue to be low for wheat planted after soybeans. During this week wheat growers in southern Ohio can start to look for development of head scab in their fields. If the predictions have been correct there should be very little disease in most fields. The exception to this may be wheat fields planted after corn where corn residue covers 10% or more of the soil surface. If the state's wheat crop remains relatively disease free for the next week or so, it is likely that Ohio will have some of the best quality wheat produced in several years. Growers are reminded to do their part by getting combines ready and start harvesting as soon as the grain dries enough to be combined. Do not put the crop at risk by letting it stand in the field after it has reached maturity. Nothing good happens to wheat in the field once the plant is mature. Rain, dew and other sources of weathering can only damage grain quality of the mature crop.

Prepare Grain Storage Facilities for Wheat

Authors: Curtis Young

The 2005 wheat harvest will start in the next couple of weeks in Ohio, and now is the time for producers to prepare their grain storage facilities to store this year’s wheat crop. Prior to storing new wheat, producers should make every possible effort to prepare a pest-free environment in which to store the grain to reduce the risk of infestation by established pest populations, especially insects. Preparations should include sanitation measures to reduce possible existing stored grain pests, bin maintenance, and if necessary, an application of an insecticide to eliminate established insect populations that can not be eliminated by sanitation measures.

Most insect infestations of stored grain originate from immigration of insects into the bins from outside. These insects may be established around the grain storage facility in piles of old contaminated grain, cleanings from grain dryers and cleaners, spilled grain, livestock feeds, pet foods, wild bird seed, crop seed, bags, litter, weeds or any other cereal products.

Newly harvested wheat may also become infested with insects when it comes in contact with infested grain in combines, truck beds, grain wagons, grain dumps, augers, bucket lifts or grain already in the grain bin from previous years. Insects may also be present in carryover grain in “empty” bins and from grain debris beneath perforated bin floors.

Sanitary practices include measures to thoroughly remove old grain, grain debris and weeds that may be supporting insect populations in and around the grain storage facility. At least two weeks before storing new wheat, brush, sweep out and/or vacuum the combine, truck beds, grain wagons, grain dumps, augers and elevator buckets to remove insect-infested grain and grain debris. Remove all grain and debris from aeration fans, exhausts and ducts. Remove all grain and debris from the storage site. Dispose of the grain and debris removed from all areas by feeding it to livestock or destroying it. Remove all vegetation growing within ten feet of grain bins and preferably from the storage facility. Apply a residual herbicide around the grain bins to prevent new weeds from growing.

Inside empty bins, walls, ceilings, ledges, rafters, braces and grain handling equipment should be swept and/or vacuumed. Insects may remain in hard-to-clean areas such as cracks and crevices in bin walls and in the plenum beneath non-removable perforated floors. Therefore, once bins are thoroughly cleaned, an empty bin insecticide treatment should be applied. The empty bin insecticide treatment should help eliminate any remaining insect infestations and create a barrier for insects that may migrate into the bin from outside. Applying an insecticide in an empty bin supplements but does not replace sanitation measures.

Apply an insecticide to the walls, ceiling and floor of all bins that will be used to store grain for more than a few weeks during warm weather. The best time to apply the empty bin insecticide treatment is two to three weeks before loading new grain into the bin. Use one of the following products: Reldan 4E (chlorpyrifos-methyl (6 ppm))(Do not apply Reldan to bins that will be used to store corn or soybeans), Diacon II (s-methoprene), Storcide II (deltamethrin and chlorpyrifos-methyl (3 ppm)), Tempo 20WP (cyfluthrin), Tempo SC Ultra (cyfluthrin) or diatomaceous earth. These materials may be applied to the outside of the bin as well to produce an additional barrier to outside insects. Unless insecticide labels specify otherwise, spray all bin surfaces to the point of runoff and be sure to treat all cracks and crevices and around doors thoroughly. Whenever using insecticides, be sure to read the entire product label for proper application rates and use restrictions.

A special note on Reldan 4E - this product is having its registration voluntarily cancelled. It is available for sale through December 31, 2005. Supplies of Reldan 4E should be used over the next few years. Grain with residues of the Reldan 4E product at a level of 6 ppm will be rejected if detected at grain terminals.

A special note on Malathion products - there was once numerous malathion products that carried stored grain usages on their labels. Most malathion products have removed such usages from their labels. Now, new labels for recently purchased malathion products carry the statement of “Do Not Apply Directly to Grain” and thus should only be used around the outside of bins and other grain handling structures (e.g. Malathion 5EC (57% malathion)). Other malathion products may have no grain handling facility usages at all. If one is considering a malathion product, read its label very carefully before using.

A special note on Methoxychlor - this insecticide had been registered for a wide range of usages in a multitude of arenas including in and around stored grain facilities. As of June 30, 2004, the Environmental Protection Agency has completed methoxychlor’s re-registration evaluation and decided that it was not eligible for maintaining its labeled usages. Thus, its registration has been cancelled, and all tolerances for its residues have been revoked. Unlike Reldan 4E, any stocks of methoxychlor that one may have on their farm or grain handling facility SHOULD NOT BE USED!

Fumigating empty bins to control insects in the sub-floor plenum may be necessary if wheat is to be stored in the bin one month or longer. Empty bin fumigation usually is not necessary if wheat is to be treated with a grain protectant insecticide at the time of loading the bin. Be sure to check with your grain purchaser as to what insecticide residues are acceptable on the wheat before treating wheat with a grain protectant. The fumigant chloropicrin is labeled and effective for empty bin fumigations.

Chloropicrin is a restricted use pesticide that is extremely toxic. Chloropicrin forms a pungent, tear gas that is heavier than air and will settle into the bin’s sub-floor area. Approved respiratory protection and gas monitoring equipment are required when using chloropicrin. If you are uncertain about the safe use of chloropicrin, contact the manufacturer for detailed recommendations. Chloropicrin may be very difficult to obtain. It is no longer permissible to ship chloropicrin in the mail, thus if a local dealer does not have the product on hand it will be unavailable.

And one final note, do not store newly harvested wheat on old wheat already in the grain bin.

Soybean Population Determinations

Authors: Greg LaBarge

This is a good time to make determinations of soybean populations and evaluate how well your planter or drill did in seed placement this year. As seed cost increase this is a area where cost controls can be found. Two common methods can be used to determine soybean populations the Hula Hoop and row spacing methods.

The Hula Hoop method is a function of the number plants counted in a certain diameter hoop. The table below has the multiplier used based on hoop size.




For example an average of 20 plants in a 28 inch diameter hoop would be multiplied by 10,200 or 20 * 10,200=204,000 plants per acre.

The row spacing method is described next. You can use this simple formula determine population per acre:

6,272,640 sq. inches per acre / (average seeds per inch * row spacing) = plant population per acre

For example where the average plant spacing in 10 inch rows is 3.5 inches between plants the population would be 179,000 plants per acre= 6,272,640/(3.5*10)

Wheat Production Field Day in Northwest Ohio June 21

Authors: Patrick Lipps

The Ohio Agricultural Research and Development Center will be holding a Wheat Production Field Day form 9:00 am to noon on Tuesday, June 21, 2005 at the Northwest Agricultural Research Station near Hoytville, OH. The station is located one mile east of SR235 between Hammansburg and Oil Center roads in Wood County. All wheat growers and persons involved in wheat production are invited to attend. Presentations will be given on wheat disease identification, scouting and fungicide usage; wheat variety and row spacing interaction effect on yield; managing nitrogen and sulfur in wheat; and an update on wheat breeding at OARDC and new variety releases. In addition, representatives from the Ohio Wheat Growers Association will present an update of their resent activities to help wheat production in Ohio. Please come and take this opportunity to speak with the researchers and ask questions relative to your wheat production problems. The Northwest Agricultural Research Branch is located at 4240 Range Line Rd. A map can be found at

“Let’s Get Ready” Scouting and Sprayer Clinic June 21

Authors: Dusty Sonnenberg

A free field scouting and sprayer adjustment clinic has been scheduled for Tuesday, June 21st, at the OARDC Northwest Research Station near Hoytville, from 1:00 p.m. – 4:00 p.m. OSU Plant Pathologists, Dr. Anne Dorrance, and Dennis Mills will be on hand to help identify and discuss what diseases we are currently seeing in our crops and their associated thresholds. OSU Entomologist, Dr. Ron Hammon, will be discussing insect pressure and soybean aphid issues. OSU Agricultural Engineer, Dr. Erdal Ozkan, will be discussing sprayer set-up, adjustment, and tip selections.

Private and Commercial Pesticide Applicator Credits as well as Certified Crop Advisor CEU’s will be available that day. Hands-on field scouting for various insects and diseases, as well as an in field sprayer demonstrations utilizing various pressures, volumes and speeds will be conducted. A spray table will also be utilized to compare various nozzle types and spray patterns.

OARDC will be holding a Wheat Production Field Day that same morning, so producers can come and make a day of it. The Wheat Field Day runs from 9:00 a.m. – 12:00 noon. The McComb FFA Chapter will be on hand with a lunch stand so you can buy your lunch there and support the FFA, and then stay for the afternoon clinic.

For more information contact Dusty Sonnenberg at OSU Extension in Henry County at (419) 592-0806, or by e-mail at

Archive Issue Contributors: 

State Specialists: Pat Lipps & Anne Dorrance (Plant Pathology), Peter Thomison (Corn Production), Mark Loux (Weed Science), Jeff Stachler (Weed Science), Bruce Eisley (IPM) and Ron Hammond (Entomology) Extension Educators: Roger Bender (Shelby), Todd Mangen (Mercer), Steve Foster (Darke), Greg La Barge (Fulton), Glen Arnold (Putnam), Howard Siegrist (Licking), Mark Keonig (Sandusky), Harold Watters (Champaign), Ed Lentz (Seneca) and Steve Prochaska (Crawford).

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.