Corn Newsletter : 2018-20

  1. Foliar Fungicide Use in Corn

    grey leaf spot
    Author(s): Pierce Paul

    Foliar diseases, especially Gray Leaf Spot (GLS), are beginning to show up in some corn fields. This is not at all surprising, given that the crop was planted relatively late and it has been wet and humid in some areas. GLS is favored by humid conditions, particularly if temperatures are between 70 and 90 F. Foliar diseases of corn are generally a concern when they develop early and progress up the plant before grain fill is complete. This is especially true when the hybrid is susceptible. In most years, GLS and NCLB usually develop late or remain restricted to the lower leaves. However, if it continues to rain and stays humid, this will likely not be the case this year.

     

    Due to wide variations in planting dates, weather conditions, and hybrid maturities, the corn crop is at growth stages ranging from emergence to tassel across the state. Now is the time to start scouting those early-planted fields for foliar diseases, especially those planted with susceptible hybrids in an area with a history of foliar diseases or in a continuous-corn, no-till fields. Those are the fields most likely to benefit from a fungicide application. Use hybrid susceptibility, weather conditions, field history, and current disease level as guides when making a decision to apply a fungicide.

     

    Based on years of research, we have found that applications made at silking (R1) or tasseling (VT) are the most effective in terms of foliar disease control and yield response in Ohio. Although we have seen a yield response to treatments applied between V4 and V10 in some years, the average yield increase is often low and highly variable when fungicides are applied before VT/R1. Similarly, on average, the yield response is much lower and more variable when fungicides are used under low disease pressure or in the absence of foliar diseases, than when disease is present.

     

    There are several very good fungicides to choose from. Follow the labels and keep your eyes on the fungicide price and application cost when making a decision. Use the information below to help you make your fungicide application decision:

    • Susceptible hybrids: If disease symptoms are present on the third leaf below the ear or higher on 50% of the plants examined, a fungicide is recommended.
    • Intermediate hybrids: If disease symptoms are present on the third leaf below the ear or higher on 50% of the plants examined, AND the field is in an area with a history of foliar disease problems, the previous crop was corn, and there is 35% or more surface residue, and the weather is warm and humid through July and August, a fungicide is recommended.
    • Resistant hybrids: Fungicide applications generally are not recommended.

    Corn Fungicide Table

  2. Does Timing Matter When Sampling Corn and Soybean Tissue for Nutrient Analysis

    Tissue analysis can play an important role in determining if corn and soybean are getting adequate nutrition. Tissue samples can be pulled at various stages of development, but one of the most common times is when crops enter the reproductive stages (R1). Prior to R1, corn and soybean are in a rapid growth phase with very high nutrient uptake over several weeks. Sampling at R1 allows us to determine if their nutrient needs are being met, or if a particular nutrient is deficient. But how important is it that the tissue sampling happen right at flowering? If the sampling is a little earlier or later, will you get different results?

    We addressed these questions by sampling 6 corn and 6 soybean fields across Ohio (Darke, Highland, Mercer, Miami, Paulding, Ross and Wayne County). At each field, leaves were sampled 2 weeks before, 1 week before, at flowering (R1), 1 week after, 2 weeks after flowering. Tissue samples were dried and analyzed for total nutrient concentrations. The Tri-State Fertilizer Recommendations has sufficiency ranges that indicate if tested samples are ‘below, ‘sufficient’, or ‘above’ normal levels.

    The two figures below show macronutrient concentrations with trendlines over the 5-week period for corn and soybean. Over all the sites, macronutrient concentrations varied widely, representing differences in fields, hybrids or varieties and environments. Some nutrient concentrations increased or decreased, while others remained consistent over time. These results demonstrate that nutrient concentrations do fluctuate before and after R1. Therefore, care should be taken to sample as close to flowering as possible, so that the lab results obtained are consistent and meaningful with published reference values (Table below).

    Corn Ear Leaf Nutrient Concentrations

    Soybean Trifoliate Nutrient Concentrations

    Nutrient sufficiency ranges at flowering

    Nutrient

    Corn

    Soybean

     

    --------------------- (%) ---------------------

    Nitrogen

    2.90 – 3.50

    4.25 – 5.50

    Phosphorus

    0.30 – 0.50

    0.30 – 0.50

    Potassium

    1.91 – 2.50

    2.01 – 2.50

    Calcium

    0.21 – 1.00

    0.36 – 2.00

    Magnesium

    0.16 – 0.60

    0.26 – 1.00

    Sulfur

    0.16 – 0.50

    0.21 – 0.40

    (Adapted from Table 24 of Tri-State Fertilizer Recommendations)

  3. Western Bean Cutworm Montoring

    Western bean cutworm adult

    Another season of Western bean cutworm (WBC) trapping has officially begun! Bucket traps placed along the edge of a corn field with a lure were set between June 17th through 23rd and our first trap count is for WBC adults captured for week ending June 30th. Last week, 18 counties monitored 66 traps across Ohio for WBC adults. Overall, 76 WBC adults were captured and average moth per trap was 1.2 (Figure 1).

    Figure 1. Average Western bean cutworm adult per trap followed by total number of traps monitored in parentheses for week ending June 30, 2018.

    The adults begin to emerge in late June and peak flight occurs anytime between the 2nd through 4th week of July (Figure 2). Monitoring for the adults allows us to pinpoint the optimal time to begin scouting for egg masses as well as know when peak flight is across the state. It is important to note that WBC prefers to lay eggs in pre-tassel corn— and since the rain delayed planting in many parts of the state this year, Ohio has a lot of late planted corn. Therefore, a good scouting program is important!

     

    Figure 2. Western bean cutworm adult.

    More information on our trapping summary for the 2017 field season can be found here: https://agcrops.osu.edu/newsletter/corn-newsletter/2017-29/western-bean-....

    Further information on WBC can be found in our fact sheet: http://ohioline.osu.edu/factsheet/ENT-40 and a free article in the Journal of Integrated Pest Management: http://jipm.oxfordjournals.org/content/1/1/A1

  4. Final Kudzu Bug Monitoring Update

    Department of Entomology, The Ohio State University

    Kudzu bug monitoring in Ohio is now complete with zero kudzu bugs found in the nine counties in Ohio that participated in monitoring (Figure 1). Overall, 15 PVC traps were monitored in nine counties including, Adams, Athens, Butler, Clermont, Madison, Meigs, Montgomery, Ross and Washington. Traps were set in May were checked weekly through June. Although the kudzu bug has yet to be found in Ohio; it is important to continue future monitoring efforts due to the continuation of expanding distribution. If you suspect kudzu bug in your county please contact your local extension office.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    Figure 1. Average number of kudzu bug / total number of traps located in each county participating in the kudzu bug monitoring (highlighted in red).

  5. Mark Your Calendars for These Important Field Days

    The OSU/OARDC Western Agricultural Research Station will host two field days in July. The OSU Weed Science Field Day on July 11th, and the Western Agronomy Field Day on July 18th.

    The OSU Weed Science Field Day will be held on July 11 at OARDC Western Ag Research Station at 7721 South Charleston Pike (SR41), South Charleston Ohio. As in previous years, it’s a mostly self-directed event and a chance to look at all of our research. The day runs from 9 to noon, followed by lunch for those who preregister. Feel free to bring anyone you like and to tell others, but please send an email to Bruce Ackley to preregister - ackley.19@osu.edu - telling him how many are coming so he can plan appropriately. The registration fee $35, includes lunch and the plot book, payable on the day of the tour. We will be around as usual to answer questions and lead some brief discussions.  

    The Western ARS Agronomy Field Day will be held July 18th from 9 AM to 3 PM. No charge this year as we are soliciting sponsors to offset that cost. Lunch is included, and we will of course have in-season updates as well as talk about some on-going research. The location is the Western Agricultural Research Station at 7721 So. Charleston Pike, South Charleston south of I-70 and just west of the Ohio 54 and SR 41 intersection or from the west exit from I-71 onto SR 41, south, drive about 4 miles and you will see the station on the right.

    Topics and speakers include:

    • Keynote speaker: Robert Mullen, Chief Agronomist with Nutrient. Robert has much Ohio and international experience and will share his insights on nutrient management.
    • Weed Challenges this Season – Mark Loux
      • And back by popular demand is the mode of action weed screen plots. Walk through them and see what happened and why.
    • Ohio Soil Fertility Research Update; leading to the new fertilizer recommendations to come out later this season - Steve Culman
    • Water Quality and Fertilizer Application Research update; this work is what will bring the new P-Index to Ohio - Libby Dayton
    • Precision Planting and Smart Seed Firmers - Alex Lindsey
      • Can knowing your organic matter, soil temperature and soil type help you make seed depth decisions at planting?
    • Disease and Insect Scouting School – Kelley Tilmon, Anne Dorrance, Pierce Paul, and Andy Michel
      • This class to close out the day, will be hands on help for mid-season scouting of insects and diseases. Want to know what else may pop up this summer? You will learn from the experts.
    • CCA continuing education credits will be available.

    Pre-registration for the field day is required by July 11, 2018. Registration online at https://www.surveymonkey.com/r/wars2018, by email to Joe Davlin, davlin.1@osu.edu or Harold Watters, watters.35@osu.edu. For more information or to register by phone call the farm at 937 462-8016.

    The OSU/OARDC Western Agricultural Research Station is one of three agronomy research stations across the state. The Western Agricultural Research Station maintains intensive research programs that address the profitability and sustainability of western Ohio's most important agricultural industries: agronomic crops (corn, soybeans, and wheat among them); specialty crops (such as pumpkins and sweet corn); and swine production. Additionally, the Western Station is home to one-of-a-kind studies on no-till crop production, carbon sequestration in no-till farmland, and bio-energy crops: https://oardc.osu.edu/facility/western-agricultural-research-station.

About the C.O.R.N. Newsletter

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.

Contributors

Anne Dorrance (State Specialist, Soybean Diseases)
Chris Zoller (Tuscarawas County)
David Dugan (Adams County)
Dean Kreager (Licking County)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Eric Richer, CCA (Fulton County)
Garth Ruff (Henry County)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Harold Watters, CPAg/CCA (Field Specialist, Agronomic Systems)
Jeff Stachler (Auglaize County)
John Schoenhals, CCA (Williams County)
Lee Beers, CCA (Trumbull County )
Mark Badertscher (Hardin County)
Mike Gastier, CCA (Huron County)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Rory Lewandowski, CCA (Wayne County)
Sam Custer (Darke County)
Steve Culman (State Specialist, Soil Fertility)
Wayne Dellinger (Union County)

Disclaimer

The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made 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.

CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.