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April 15-22, 2002
C.O.R.N. 2002-9
In This Issue:
A) Update On Ohio Wheat Growth And Development
B) Black Cutworm Moths Are Flying
C) Slug Management
D) Bean Leaf Beetle Early Season Control & Soybean Viruses
E) Early Soybean Aphid Management Considerations
F) Reminders On Herbicide Restrictions On Wheat
G) Reminders On Herbicides For Rapid Burndown Of Winter Annuals
Warmer weather over the past week has enhanced wheat growth throughout the state. Most wheat fields in southern Ohio are now jointing. I visited fields by Circleville and Chillicothe last Wednesday. About half the fields had tillers with the first nodes visible which corresponds to Feeke's growth stage 6. Fields in northern Ohio are not so advanced. At Wooster the wheat planted on the Hessian Fly safe date are now in growth stage 5 and later plantings are at growth stages 3 to 4. Most wheat in northwest and north central Ohio had just begun to re-grow last week and may still have time to produce more tillers. The warm weather predicted for this week will promote rapid growth of the crop. You can determine when wheat is in growth stage 6 by digging plants from the field. Pull individual tillers from the plants and strip down the lower leaves on the 'stem'. The first node can be recognized as a hard swelling anywhere from one half inch to two inches above the roots. It is generally best to have your nitrogen top-dress on the wheat by this growth stage. Additionally, be advised that you should evaluate the growth stage of the crop before applying certain herbicides which have growth stage restrictions.
Our suggestion to deal with BCW is to scout fields as soon as the corn begins to sprout and emerge from the soil. Rescue treatments can then be applied if necessary. If a field is extremely weedy a preventive insecticide treatment at planting might help to prevent serious cutworm injury. However, there isn't any way to determine which weedy field might have a problem before planting. For additional information about BCW and other early season pests of corn, see OSU FactSheet FC-ENT-12 at http://ohioline.osu.edu/ent-fact/0012.html.
There are a number of insecticides that are currently labeled for use on corn against cutworm. Some can be used as either preventive or rescue treatments, while others are labeled only for rescue treatments. Check the label before using. Insecticides labeled for cutworm on corn include:
Ambush* @ 6.4 to 12.8 fl oz/A
Asana* XL @ 5.8 to 9.6 fl oz/A
Capture* 2EC @ 2.1 to 6.4 fl oz/A
Lorsban* 4E @ 2 to 3 pints/A
Mustang* @ 1.4 to 3.0 fl oz/A
Penncap-M* 4 pints/A
Pounce* 3.2EC @ 4 to 8 fl oz/A or 25 WP @ 6.4 to 12.8 oz/A
Pounce* 1.5G @ 6.7 to 13.3 lb/A
Sevin (several formulations) @ 2 to 3 lb a.i./A
Warrior* 1CS @ 1.92 to 3.20 fl oz/A
Several of the soil insecticides have activity against BCW. Check the label for activity.
* Use is restricted to certified applicators.
Slug population densities were moderate to heavy in many
fields in the fall of 2001. These numbers suggest that spring populations might
be high. Corn and soybean growers who have had problems with slugs in the pasts
should plan on monitoring their fields closely for slug populations and injury.
Growers should realize that tillage continues to be an option for management
of slugs in both corn and soybean fields. Tillage lowers the potential for damage
because it removes the residue that provides a favorable slug habitat. However,
the use of tillage should be weighed against the benefits of no-tillage production
practices.
Because slug damage to soybeans often occurs at germination
and emergence resulting in significant stand loss, growers with higher slug
populations and a history of poor soybean stands due to slugs might want to
consider an at-planting time application of molluscicide bait. Growers are advised
to determine if slugs are present and active at the time of soybean planting
in order to make the appropriate decision. This is best done by searching at
the soil level underneath the crop residue for the presence of slugs and/or
slug eggs. If slugs have hatched and are active at planting, treatment might
be warranted.
When treating, the most commonly used molluscicide is Deadline MPs, which should be broadcast at 10 lbs per acre. If past history suggests that only certain areas of a field have had a problem, only those areas need to be treated. There is a new molluscicide that should be available this spring, Trail's End LG. This material should also be applied at 10 lbs per acre. Check areas, approximately 100 by 100 ft, should be left to determine the treatment's efficacy. We will continue to update the slug situation this spring in the CORN newsletter.
Growers should monitor their soybean fields for the presence
of abnormally high populations of bean leaf beetle. Although over-wintered beetles
usually do not reach economic levels in the spring, we saw fields 2 years ago
with extremely high populations causing significant defoliation, stunting of
the plants, and in some cases, stand loss. Although beetle populations last
fall were not excessively high, the mild winter this past year might have helped
the insects over-winter in higher numbers. Thus, there is a slight potential
for larger populations. Bean leaf beetles tend to be most numerous in early-planted
fields. Thus, growers who plant their soybean fields early, especially relative
to other fields in their areas, should watch their fields closely.
There were many fields in Ohio 2 years ago that experienced symptoms associated
with bean pod mottle virus. Virus symptoms included "green stem syndrome",
crinkled leaves, and mottled seeds. The bean leaf beetle vectors this virus,
especially in early season during feeding by the overwintering beetle. Some
growers in Ohio have shown interest in applying an insecticide early in the
season to prevent feeding by beetle populations and thus, the reductions in
the virus. Although we DO NOT recommend this approach at this time, there is
information from another state that is examining its potential. If a grower
chooses to use this approach, the insecticide spray should take place AFTER
the soybeans emerge, not before. There needs to be plants out of the ground
to capture the insecticide and be drawing in the beetles. Thus, a treatment
should be done following emergence but before the unifoliates expand. The research
being done in that state also indicates that the highest level of control was
achieved by applying a second application against the beetle's next generation
in mid-July. So those growers wishing to take this approach should consider
that both sprays perhaps might be needed. Over the next few years, we will continue
to examine this approach to determine whether it is appropriate in Ohio.
Soybean aphid was found damaging soybeans throughout the Midwest in 2001, including northern counties in Ohio. Yield losses between 6-12 bu/acre were common in numerous strip trials conducted throughout the Midwest. Based on the experiences of numerous people throughout the region, we are developing information that can be used as a guideline in determining the need for spraying. These guidelines will be available sometime in late May. However, there are a few issues that are important at this time.
Timing of the insecticide application will be very critical. Observations from other states suggest that the greatest benefit from an insecticide application will come during or immediately following flowering. Thus, most insecticide applications should occur in early to mid July during flowering or immediately thereafter. The later in the summer the insecticide application is made, the less the benefit from the spray. Spraying late in the season after pods have filled or following dispersal of winged aphids will be too late to prevent economic yield loss.
Our current thought is that the best control will come using ground equipment. However, growers often have a concern with driving down rows after plant canopy closure. Growers in areas of the state that experienced large aphid populations who use narrow row planting systems (the norm in Ohio) and have a large concern about the aphid might consider the use of skip-row systems. Dr. Jim Beuerlein, Ohio State Soybean Agronomist, has shown that the yield loss in skip-row systems is minimal compared to driving over rows. See the following web site for information on skip-row soybean planting systems: http://ohioline.osu.edu/agf-fact/0131.html. Check back in late May with this CORN newsletter for treatment information.
A few reminders on the use of wheat herbicides as the crop reaches jointing and wet conditions prevail:
Wet weather has delayed application of burndown herbicides
and stimulated growth of winter annuals and dandelion in some fields. Last weeks
C.O.R.N. contained an article on management of dandelion. The problem in fields
heavily infested with chickweed and other winter annuals is that these weeds
will prolong the drying of soil and interfere with planting, as well as harbor
insects. If wet conditions prevail and cause a delay in planting, it may be
necessary to use burndown herbicide programs with relatively rapid activity
in order to facilitate planting in these fields. The activity of glyphosate
will generally be more rapid in late April or early May compared to late March.
Glyphosate may therefore be an effective choice in fields where the speed of
burndown is not a critical factor or where winter annual populations are sparse.
However, where rapid burndown of chickweed and deadnettle is essential, OSU
research indicates a mixture or Sencor plus Gramoxone to be one of the more
effective treatments in soybeans. Where deadnettle is the primary target, a
mixture of Gramoxone with Canopy XL or Authority should also be effective. If
it is possible to apply at least 7 days before planting, we suggest including
2,4-D to help control marestail and dandelion. In corn fields, atrazine plus
2,4-D may be adequate for winter annual control if there is enough time between
application and planting. Where speed of burndown becomes critical, a mixture
of atrazine plus Gramoxone will be one of the more effective treatments. Keep
in mind that in addition to facilitating crop establishment, a goal of the burndown
program should be to keep winter annual weeds from going to seed in order to
minimize future problems.
Readers can subscribe electronically to this newsletter by sending an e-mail message to: corn-out-on@postoffice.ag.ohio-state.edu. A successful subscription message will receive by an automatic reply from the listserv. Contact your local Ohio State University Extension Office or e-mail labarge.1@osu.edu if you have problems subscribing.
Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/
C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.
State Specialists: Pat Lipps , Anne Dorrance , & Dennis Mills (Plant Pathology), , Mark Loux & Jeff Stachler (Weed Science), Ron Hammond (Entomology) and Bruce Eisley (IPM), Extension Agents: Roger Bender (Shelby), Clark Hutson (Seneca), Barry Ward (Champaign), Greg La Barge (Fulton), Howard Siegrist (Licking), Glen Arnold (Putnam) Gary Wilson (Hancock), David Jones (Paulding), Alan Sundermeier (Henry), Dennis Baker (Darke), and Steve Prochaska (Crawford).Editor: Steve Prochaska Web Editor: Tom Rosati
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
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.
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