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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2011-21

Dates Covered: 
July 5, 2011 - July 12, 2011
Amanda Douridas

Postemergence control of marestail?

Marestail is abundant in some soybean fields at this time, and we have been receiving questions about options for POST control.  There is not a lot of good news here unless the field is planted with LibertyLink soybeans.  POST soybean herbicides with activity on marestail include glyphosate (RR soybeans), Ignite (LibertyLink soybeans), chlorimuron (Classic, Synchrony), and cloransulam (FirstRate).  Most of the marestail populations are resistant to glyphosate, and some of these are resistant to chlrimuron and cloransulam also.  The latter two herbicides are effective primarily on small marestail seedlings.  The bottom line is that is will most likely not be possible to control the marestail in many fields.  

Where control will be attempted, we suggest a combination of glyphosate (1.5 lbs ae/A) plus either Classic (2/3 to ¾ oz/A) or Firstrate (0.3 oz).  It’s possible that the combination of this mixture and a well-developed soybean canopy will suppress marestail somewhat.  It’s important to try to prevent marestail plants from going to seed however possible.  This could include removal by hand, or going through marestail infestations with a mower raised above the soybeans.  Control of marestail and prevention of seed production is also essential in in fields that are fallow or being planted to double-crop soybeans.  See the article from June 29, 2010 C.O.R.N. issue on this issue -

Western Bean Cutworm Catch Update

Catches of western bean cutworm have increased from a few to 59 as of July 5 (see our updated map at  Interestingly, this is about the same amount caught last year at this time, despite the cooler spring in 2011.  However, we have slightly more traps this year, and may also be receiving migrants from other neighboring states that are also reporting catches. We have probably not yet reached peak flight, so continued monitoring of adult traps is warranted, and, if possible, more frequently.  Should you begin to catch moths on consecutive nights, egg scouting should begin.  See our article last week for egg scouting procedures.  One reminder: corn varieties containing Cry1F (Herculex or SmartStax brands) or Vip3A (Viptera) offer protection and control from western bean cutworm; however, refuge plants will still need to be inspected.

Soybean Aphid Update early July

Back in April of this year, we wrote an article (April 11, 2011-08) where we predicted that Ohio would see soybean aphids this summer, albeit that we could not say if any part of the state would actually experience outbreak conditions.  We can report that the prediction of having aphids might become true.  States and provinces to our north and northeast (Michigan, New York, Ontario) are starting to report seeing soybean aphids in numerous fields at low levels, and we can report that we know of at least a field each in Wayne and Wood Counties in Ohio (early planted soybean fields), that have small aphid populations.  Because we feel that most of Ohio’s problems in later summer come from aphids that migrate from northern areas, conditions are beginning to occur that might provide us with larger populations in a month or so.  Thus, while absolutely nothing should be done at this time other than keeping watch, we would urge growers to keep vigilant, not only what is beginning to happen in Ohio, but what is occurring to our north.   At this time, we would urge growers to NOT take any preventive action against the soybean aphid, and wait until economic levels begin to occur, if they do.  Please see the following article in regards to this.

The Case Against Preventive Insecticide Treatments

We were aware that as wheat fields were treated with fungicides this past spring, many were also treated with an insecticide that was thrown into the tank because “it’s cheap insurance”.   We would offer the reminder that this is completely against IPM philosophy.  However, we accept the view that because the insecticide was relatively cheap compared with the high price of wheat, it was easy for growers to make this decision.  

We want to bring this concept of preventive treatment up again as we move into decisions regarding corn and soybean fungicide, and even with herbicide treatments.  We would ask if applying a preventive insecticide is worth the risk.  We realize it is hard to make the case from the monetary aspect of the decision; the cost of the insecticide is probably lower than a bushel of corn or soybean.  But as we do in all our talks, consider all the other negative aspects of unnecessary insecticide use.   The primary concern is the killing off of beneficial insects, our allies in keeping pest populations at low levels.   This benefit is not only to the pest in question but also with other pest species on the crop, and often other pests in nearby fields.  A second concern is the potential of resistance developing to the insecticides.   This is not a major problem yet in most field crops in the Midwest, which is partially because of our past success in keeping unnecessary insecticide applications to a minimum.  

Another concern is the problem with spray drift that can cause problems to nearby bee hives.  While neither corn nor soybean are heavily visited by bees except perhaps for the weeds that are flowering in the fields, any additionally spray drift that might occur with greater pesticide application might lead to more problems for the bees.  Finally, we would point out the environment itself.  While all of us accept the usefulness of insecticides in growing and producing our crops, we will all need to respect the environment and always take actions to prevent further damage to our soils, waterways, and overall ecosystem.  Using pesticides only on a needed basis, and the case of insecticides, using economic thresholds, we will continue to accomplish this.  We do not want to give those groups that want to take away these very useful tools in crop production more reasons and ammunition to go after them!

Nutrient Value of Wheat Straw

As the wheat harvest progresses, we get questions on the nutrient value of straw. The most accurate value would be to send a sample to one of the analytical laboratories, which would account for the weather and other factors that occurred this year. However, often a producer does not want to hassle with a lab sample and just wants a ball park figure to estimate nutrient removal and its potential value as a nutrient source.  For these individuals, Dr. Robert Mullen reported in previous newsletters that a ton of wheat straw would provide approximately 11 pounds of N, 3 pounds of P2O5 and 20 pounds of K2O. These would be legitimate numbers to use as estimation.  Most of the nutrient value is potash, some as N, and little as phosphorus.  A dollar amount may be added by using current fertilizer prices to these values.  Besides providing nutrients, straw has value as an organic matter to a soil, but it is difficult to determine the dollar value for it. Removal of straw does lower soil potash levels, but a soil test should be done to accurately estimate future crop availability.

New Forage Seedings, a Unique Opportunity This Summer

With the weather allowing so few new forage seedings to be established in Ohio this spring, not only do many acres originally intended for forages remain unplanted, but several thousand acres intended for corn and soybeans are also still vacant. With the prime time for a summer forage seeding less than 5 weeks away, our spring weather issues offer a unique opportunity for forage growers  to be prepared to make the perfect summer seeding when August arrives.
In particular, soil samples can be pulled now in order that corrective lime and fertilizer applications may be made in a timely fashion. The extra time available to prepare for new seedings this year also allows growers to eliminate perennial weeds, and control the annuals which continue to germinate while abundant precipitation persists throughout the state.
OSU Extension Forage Specialist Mark Sulc offers the following 11 highlights of key management steps toward successful establishment of perennial forages for later this summer.

1. Apply lime and fertilizer according to a soil test. Since the stand will be used for several years, ideally the soil test should have been taken within the past year. If soil pH is low, corrective applications will not take effect quickly enough for good establishment this year of pH sensitive species like alfalfa.

2. Control problem perennial weeds ahead of seeding. Be careful with herbicide selection because some have residual soil activity and will harm new forage seedings if proper waiting periods are not observed. Be sure to read the labels of any herbicides being considered.

3. Plant new perennial forage stands as soon as possible in August. Seedlings require at least 6 to 8 weeks of growth after emergence to have adequate vigor for winter survival. In northern Ohio, plant during the first two weeks of August. In southern Ohio, plant by August 30. Assuming soil moisture is present, planting earlier in August is almost always better than later. Later planting than these recommended dates may work, but there is greater risk for failure and the stand may have lower yield potential next year. The new stand should have at least six to eight inches of growth before a killing frost. Slow establishing species should be planted as early as possible. Fast establishing species like red clover, alfalfa, and orchardgrass can be seeded up to the dates listed above if moisture is present. Kentucky bluegrass and timothy can actually be seeded 15 days later than the dates listed above.

4. It is risky to place seeds into dry soil – there may be just enough moisture to germinate the seed but not enough to get the seeding established. Either plant soon after a rain when soil moisture is adequate, or when a good rain system is in the forecast.

5. No-till seedings conserve moisture and can be very successful, provided weeds are controlled prior to seeding. Remove all straw from fields previously planted to small grains. Any remaining stubble should either be left standing, or clipped and removed. Do not leave clipped stubble in fields because it will form a dense mat that prevents good seed placement and emergence.

6. If you are going to use tillage, don't over-till and be sure to prepare a firm seedbed. Loose seedbeds dry out very quickly. Deep tillage is not ideal for late summer seedings. A cultipacker or cultimulcher is an excellent last-pass tillage tool. The soil should be firm enough that the your footprint is no deeper than 3/8 inch.

7. Plant the seed shallow (1/4 to 1/2 inch deep) and in firm contact with the soil. Carefully check seeding depth, especially when using a no-till drill. A drill with press wheels provides the greatest success with summer seeding. Broadcasting seed on the surface without good soil coverage and without firm packing is usually a recipe for failure in the summer.

8. Use high quality seed of known forage-type varieties from reputable dealers. Cheap seed often results in lower yield and shorter stand life. Check out our variety performance trials and those of neighboring states at the following websites:


9. Make sure legume seed has fresh inoculum of the proper rhizobium to ensure nitrogen fixation. If the seed is pre-inoculated, check with the seed supplier to ensure the seed was stored under conditions that guarantees viable inoculant.

10. If planting alfalfa, don't plant new alfalfa immediately after an older established alfalfa stand. Autotoxic compounds are released by old alfalfa plants, which inhibit growth and productivity of new alfalfa seedlings. You can seed in alfalfa in late summer to thicken up a new alfalfa seeding that was made this spring. The autotoxic compounds are not present in young alfalfa plants. They are released from older, established alfalfa plants.

11.  As the stand develops this fall, do not be tempted to harvest it. No matter how much growth accumulates, it is usually best to let the cover protect the new crowns during the winter. The only exception to the no fall harvest rule for late summer seedings is perennial ryegrass. If perennial ryegrass has tillered and has more than six inches of growth in late fall, clip it back to 3 to 4 inches in November or early December. Finally, scout new seedings for winter annual weeds in October. Apply herbicides as needed. Winter annual weeds are much easier to control in late fall than they will be next spring.
Seldom do we relish the thought that we have nearly 5 weeks to prepare to do a permanent or long term forage seeding. Frankly, most of us hope we don't have this opportunity again . . . at least not for the reasons we currently are dealing with. Regardless, don't miss this chance for make the perfect forage seeding which could last for years!

Soybean Disease update for July

Soybeans were planted late and double crop planting has started in Ohio.  For most of the state soybean stands look good.  There are a few things to think/plan for at this time of year.

1.        Soybean rust.  The cold winter temperatures and hot dry spring prevented soybean rust from surviving in Louisiana, Mississippi, and Alabama.  In Florida, soybean rust is in a kudzu patch just south of the panhandle.  This low level of inoculum and hot dry conditions in the south indicate that it is going to take quite a bit of time to reach Ohio.  The next time we should look at this is in early August.  At this time we will take a look at how many counties in the south are red, how much inoculum is there in those locations, and what the growth stage, canopy closure, and general health of the Ohio soybean crop is. We will be able to predict what the risk is of soybean rust to actually arrive in Ohio during 2011.

2.       Phytophthora root rot:  we are finding plants with symptoms of severe root rot – primarily in areas that have been getting consistent rains.  For some varieties without a high level of partial resistance (susceptible lines where the Rps gene is no longer effective) to Phytophthora will see a thinning of the stands.  This will continue throughout the season and the stem rot phase of the disease can best be seen about 1 week after a rain.  Other root rots are also present, Fusarium, Rhizoctonia and Pythium spp.

3.       Foliar diseases:  Brown spot is showing up now in some fields where there was a high level of residue.  Symptoms are tiny brown spots on unifoliates and some of the first trifoliates. Leaves will turn yellow around these brown spots and will fall off early.  Frogeye leaf spot has not been found in Ohio, yet.  In this foliar disease, the spot is larger and has a gray center surrounded by a deep purple ring.  Some herbicides will also cause a similar type spot.  To tell the difference, put the leaves with lesions in a plastic baggie with a moist paper towel overnight.  The next day, on the underside of the leaf, there will be black “whiskers” or the conidiophores of the fungus.  If there is no “fuzz” on the back side, then it is not frogeye leaf spot.

2011 Western ARS Agronomy Field Day - Wednesday, July 20

2011 Western ARS Agronomy Field Day - Wednesday, July 20

The OSU Extension Agronomic Crops Team and OARDC Western Ag Research Station personnel will again present an agronomic crop research tour at the Western Agricultural Research Station on July 20th from 9AM to 3PM.

OARDC – Western Agricultural Research Station, 7721 South Charleston Pike, South Charleston, Ohio 45368 (3.5 miles northwest of South Charleston. Just south of I-70 on State Route 41 between Springfield and South Charleston in Clark County). The site has 428 acres in crop and swine production – with over 150 crop research projects alone. For more information on the branch:

Pre-registration required - $20 per person

For more information on the farm contact Joe Davlin, 937 462-8016

To register contact Harold Watters, at the OSU Extension Office Champaign County, 1512 South US Hwy 68, Suite B100, Urbana OH 43078, 937 484-1526,    

The combined morning wagon tour followed up with intensive in-plot visits after lunch was suggested by past participants and has proven very popular. Plans for the day:

Check in from 8:30 to 9AM

·      Wagon tour from 9 to noon, followed by a box lunch at the site.

·      Then two opportunities for in field in-depth discussion with the specialists from 1 to 3 PM.

·      Research plots to see: Late planted corn, Forage management, Weeds, weeds & more weeds, Insects for 2011, Disease problems for 2011 and Manure as a sidedress N source.

·      State specialists in attendance: Pierce Paul, Peter Thomison, Mark Sulc, Andy Michel, Mark Loux and Amanda Meddles.

Registration and agenda are available here: Do register in advance so we can make sure we have everyone covered for lunch.

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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.