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 IN THIS ISSUE...  June 2002

Prognosis Poor for Corn "Leafing Out" Underground
 Early growing season weather and seedbed conditions may create emergence problems resulting in corn seedlings leafing out underground. Seedings, which exhibit this abnormal emergence, may have a twisted appearance because internal leaves start expanding before the seeding is elongated. Several factors (or combination of factors) may be responsible for this abnormal growth. These factors may be characterized as environmental, chemical, or mechanical. Environmental conditions associated with underground leafing include light penetration, cold soils, or heavy rains soon after planting. When plants unfurl below the soil surface, they usually turn yellow and die.

In a cloddy field where soil coverage of seed is poor and irregular, sunlight can reach the germinating seedling and induce leaf emergence beneath the soil surface. Also, heavy rains after planting can cause a hard crust, which makes emergence of small seedlings very difficult. As a result, bending and twisting of the seedling below the crusted layer often occurs. Planing the seed too deep, which may cause poor germination and emergence, may also result in premature unfurling of the corn.

Certain herbicides such as Lasso and Dual, and the various premixes that contain their active ingredients can show similar symptoms (i.e. twisting, abnormal growth) when excessive rates are applied pre-emergence. Besides excessive rates, improperly closed seed furrows can allow the pre-emergence herbicide to come in direct contact with the seed. Excessive soil insecticide dosage or in-furrow placement of insecticide phytotoxic to seed can also cause twisting sprouts and abnormal leaf expansion underground. In addition, anhydrous and aqua ammonia N fertilizer injury has been associated with these symptoms. Certain corn hybrids are also more prone to this problem during emergence when unfavorable environmental conditions occur.

Corn seedlings that exhibit abnormal unfurling symptoms during emergence will be unable to penetrate any but the loosest soil even if the crust is broken mechanically or softened by rain. Prompt treatment with a rotary hoe, weeder, spiketooth harrow or cultipacker may help break the crust and improve emergence. However, even when used carefully, these salvage operations can cause some damage to seedings, which are emerging normally. To minimize poor seedling emergence due to unfurling below the soil surface, watch for cloddy seedbeds, open seed furrows, and crusing surface soils after rains. Also check planting depth periodically and adjust accordingly during the planting operation and monitor herbicide and soil insecticide rates.

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Herbicide Programs for Non-Roundup Ready Soybeans
Continued wet weather will cause producers to switch from corn to soybeans in some fields, and there may not be enough Roundup Ready soybeans to meet this added demand. Some things to consider for those fields that have recently been planted or will be planted with non-Roundup Ready soybeans within the next several weeks:

-There may be little for preplant or preemergence herbicides in many soybean fields, since the majority of this year's weed population has probably already emerged (especially in no-till fields). The reduced weed populations after planting and relatively rapid soybean growth should increase the effectiveness of single-application postemergence herbicide programs. Rainfall usually becomes more infrequent as the season progresses, increasing the possibility that preemergence herbicides will not receive enough rain in time to become active and control the first flush of weeds that emerges after planting.

-To facilitate the implementation of postemergence herbicide treatments, make sure the field is free of weeds at the time of planting. Apply glyphosate of Gramoxone as necessary before soybeans emerge to ensure a weed-free field. While we suggest the use of preemergence herbicides in some situations (see below), be aware that mixing preemergence herbicides with glyphosate can reduce the activity of glyphosate on certain weeds. Large weeds and thistle patches in many fields may require maximum glyphosate activity. Therefore, applicators will have to weigh the advantages versus the possible disadvantages of mixing preemergence herbicides with glyphosate.

-Giant ragweed, common lambsquarters, and waterhemp are weeds that may justify some type of preemergence herbicide treatment, even with the late planting. Although populations of these weeds will be reduced this late in the season, they are still among the most difficult to deal with in postemergence programs. Giant ragweed and waterhelp are weeds that can emerge through mid-summer, so consider a reduced rate of a preemergence product to reduce the population and allow for slightly later postemergence application. Preemergence herbicides with significant activity on giant ragweed include Camopy XL, Scepter, Backdraft, FirstRate, and Gauntlet.

-Control of lambsquarters with postemergence programs requires the use of Raptor or Harmony GT. Controlling lambsquarters with about $6 per acre of preemergence herbicide allows for more flexibility in postemergence herbicide and adjuvant choice, which can result in better control of most other weeds and less crop injury. Some possible preemergence options for lambsquarters control: 4 to 6 oz of Sencor, 1.5 oz of Valor, 2.5 oz of Canopy XL, or 1.4 oz of Scepter (or the rate of Backdraft that provides this amount of Scepter). Pursuit and Extreme should also provide sufficient residual control of lambsquarters through mid-summer.

-In OSU research, late-planted soybeans seem to be most likely to suffer yield loss from excessive herbicide injury, since there is less time to recover from injury compared to early-planted soybeans. Therefore, avoid the use of injurious herbicide mixtures. Applying postemergence herbicides when weeds are less than 4 inches tall improves herbicide effectiveness and reduces the need for "cocktails" that might cause excessive injury.

-Mixing postemergence broadleaf and grass herbicides can result in reduced grass control due to antagonism between herbicides. This is more likely to occur on yellow foxtail, barnyardgrass, and crabgrass, since these are generally more difficult to control than giant foxtail. With regard to grass herbicide choice, antagonism has been most evident for Assure II, and lease evident with Select, with Fusion and Poast/Poast Plus somewhere in between. Antagonism will bee more likely when nonionic surfactant is the spray adjuvant, so use crop oil concentrate if possible.
-Some producers have switched to Roundup Ready soybeans because of problems with ALS-resistant weed populations. When switching from corn to soybeans, any remaining Roundup Ready soybean seed should be planted in fields with known ALS resistance problems. Where this is not possible, herbicide programs should be built around PPO-inhibiting herbicides such as Flexstar, Cobra, or Ultra Blazer. OSU research has shown Flexstar to be the most consistently effective of these for common and giant ragweed control. The use of Basagran with these products can improve ragweed control.

-Mark Loux
 CORN #5

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Some Considerations for Herbicide Programs in Late-Planted Corn
Corn planted in late May or June is likely to be less profitable than early-planted corn, due to the reduced yield potential. However, later-planted corn should also be subject to lower weed populations, since many summer annual weeds have already emerged. While total postemergence programs make sense in late-planted soybeans, the low cost and effectiveness of atrazine keeps many producers using preemergence programs even in late-planted corn.

Total postemergence herbicide programs can be somewhat difficult to successfully implement in corn for a number of reasons. Weeds can interfere with corn sooner after planting compared to soybeans, so there is an increased risk of yield loss when postemergence herbicides are applied too late. Available research indicates that weeds should be controlled in corn before they exceed 4 to 6 inches in height to avoid yield loss. Although the weeds that emerge after a properly timed postemergence application have much less affect on crop yield, they can reduce yield if present at high enough populations. Late-emerging weeds and also reach sufficient size to interfere with harvest and produce seed that causes problems in future years. So, not only is proper timing of application essential to minimize the effect of early-emerging weeds, but it can be important for the herbicides to provide at least several weeks of control after application. Another factor is the relatively narrow window for application of most grass herbicides in corn. While soybean herbicides such as Fusion and Select are effective on weeks that exceed 6 inches in height, corn herbicides such as Accent, Basis Bold, Option, and Lightning should generally be applied when grasses are not more than 2 to 4 inches tall.

Given all of these factors, there should still be some room to reduce herbicide inputs in late-planted corn. At the very least, there should be no need for a full-rate, broad-spectrum preemergence program followed by a postemergence treatment. Some ideas and considerations for corn herbicide programs at this time of the year follow (some of the information in the accompanying soybean herbicide article applies to corn also and is not necessarily repeated here):

-Taking a more flexible approach to herbicide use can allow for a reduction in herbicide inputs. For example, if you reduce preemergence herbicide inputs, you may have to occasionally make a follow up postemergence application if late-emerging weeds become a problem. If you are unwilling to scout fields and make a second application if necessary, than you should probably use labeled rates of a broad-spectrum herbicide program.

-Our experience with atrazine premix products (Bicep, Fultime, etc) indicates that they are not likely to provide acceptable control when applied to reduced rates (50% of labeled) unless followed with an postemergence treatment. The atrazine rate becomes too low to control problem broadleaf weeds, even in late-planted corn. A better approach for about the same cost might be a mixture of atrazine plus Balance, since an effective atrazine rate can be maintained. Some producers have been able to use this combination without a postemergence follow-up treatment in fields with relatively low weed populations. Another approach might be a combination of atrazine plus simazine, although simazine is less effective than Balance on grass and broadleaf weeds. Keep in mind also that late application of persistent herbicides can increase the risk of carryover into the following year.

-Where a reduced-input preemergence program is used, be sure to scout fields soon after corn emergence for weed escapes. A goal of this scouting is to observe the weed escapes when they are small, so that the lowest possible rates of postemergence herbicides can be used.

-When using a total postemergence approach, there can be a benefit to using herbicides that provide several weeks of residual control even in late-planted corn. For example, products that contain rimsulfuron (Basis Gold, Accent Gold, Steadfast) have at least some residual activity on grasses, while products that contain just nicosulfuron (Accent, Celebrity Plus) or foramsulfuron (Option) have almost none. The addition of no more than 1 lb/A of atrazine can greatly enhance the residual control of postemergence treatments.

-When applied to small broadleaf weeds in late-planted corn, the lowest labeled rates of postemergence broadleaf herbicides can be adequate. Some examples: 4 oz of Distinct instead of 6 oz; 3 oz of Hornet instead of 4 or 5 oz; 8 oz of Clarity instead of 16 oz; 2 pints of Marksman instead of 3.5 pints.

-Be aware of the maximum corn size per postemergence herbicide labels, and the growth stage at which corn becomes more sensitive to various types of herbicides. For example, corn becomes more sensitive to growth regulators (dicamba, 2,4-D) when it exceeds 8 to 10 inches or the 5th leaf stage. For most ALS inhibitors (Accent, Basis, Lightning, Hornet, etc), application should be made before the 6-collar stage or before corn exceeds 20 inches in height.

-Mark Loux
 CORN #15

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Weather Favors Slugs
We are getting reports of slug injury from various parts of the state, with the most severe problems in central Ohio with lesser amounts in the north. Growers should expect the slug problem to intensify over the next few weeks, and thus, should begin monitoring their situation and taking action if the injury is severe. The use of Deadline Mps, Trails End LG, or another molluscicide bait should be used at the recommended rate of 10 lb per acre. Growers who will be planting soybeans over the next one to two weeks should carefully monitor their situation because the next few weeks is the worst time for slug problems, especially on emerging soybeans. Slugs can be even greater problems if the seeds are planted in less than ideal conditions, resulting in seed furrows that do not close well. Slugs will crawl up and down the seed furrows eating to their heart's content. For those growers who experience a stand reduction because of slugs resulting in the need for replanting, remember that the slugs will not only still be there, but they will be bigger and consuming greater amounts. Thus, a replanting that is necessary because of slug feeding might need a molluscicide bait application even more so!

-Corn #15

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New Website for Christmas Tree Pests
Dr. Dave Shetlar, OSU Extension Entomologist for Christmas trees has posted a plethora of Christmas tree pest information, including photos of pests and damage on the new OSU Entomology website. Visit the website at http://bugs.osu.edu and click on ornamentals, and the Christmas tree resources will be listed.

Introductory Workshop on Growing Christmas Trees
OSU Extension and the Ohio Christmas Tree Association will sponsor an introductory workshop on getting into the Christmas tree business on Wednesday, June 19, 2002 starting at 5:30 p.m. at the Feisley Tree Farm at 66565 Muller Road, in Belmont. This workshop will feature Dr. Randy Heiligmann, OSU Extension Forester, who will discuss basic tree production techniques. Registration for the workshop which includes dinner is $20 per family. To register, contact The Ohio Christmas Tree Growers Association at 614-249-2426.

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One way to identify alternatives for improving the profitability and sustainability of your farming operation is to visit other farm families who are having success with changing their operations. The 2002 Ohio Farm Profitability Tour Series will give you the opportunity to visit 20 farms and markets throughout Ohio, and see first hand how some Ohio farm families are blazing new ground in the quest to remain profitable in Ohio's changing landscape.

The theme for this year's tour series is "Our Future in the Market", and special emphasis will be placed on marketing topics. See the attached tour book for a complete schedule of tours.
 
 

Sincerely,
 

Mike Hogan Extension Agent Agriculture & Natural Resources  Community Development

Ken Simeral Extension Agent Agriculture & Natural Resources Community Development

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868