Tuesday, July 23, 2013
ms_frogeye_leaf_spot

Ohio Soybeans: Management of Frogeye Leaf Spot

AgFax.Com - Your Online Ag News Source


Several reports and samples this past week with frogeye leaf spot on leaves in the upper/mid canopy.

You will be able to find pictures and a detailed factsheet of this soybean disease here.

Frogeye leaf spot is a fungal disease that is caused by Cercospora sojina.  This pathogen is typically pretty rare in the northern states, but due to the widespread planting of some highly susceptible varieties and milder winters, we now have more inoculum in the spring.  One of my previous graduate students (Christian Cruz) did the tedious work to examine soybean residue to find the viable conidia (spores).




At the end of the 2012 season, there was quite a bit of frogeye late in the season in our fungicide trials.  At present there is enough there (almost R1) to begin to plan sprays.

There has been another development with this fungus that is a bit troubling.  Numerous populations of this pathogen have been identified that are resistant to azoxystrobin (Quadris) and pyraclostrobin (Headline).  These were first found in Kentucky in 2010 and since then have also been found in states up and down the Mississippi.  To date, none have been detected in Ohio, but the truth is we have done very little sampling.

In 2007, we had frogeye develop at two of OARDC Branches on Seed Consultants line SC 9384, a susceptible line that they have very generously donated to our field studies.   Disease levels in the top canopy at the end of the season were 28.5% and 47% at Northwest (Wood County) and Western (Clark county) Branch research stations.  The disease was only present in the top canopy at Hotyeville, so fungicide applications were made at the R5, but had very little impact if any. There were no yield differences.

Western had a different story.  At this location, the mid canopy foliage also was more than 40% of the leaf area affected and yield loss was approximately 19% when the best fungicide treated plots (65 to 69 bu/A) were compared to the nontreated (Mean 54 bu/A).

Fungicides applied at R1 on these indetermimant soybeans were not significantly different than the nontreated.  I think that this is due to the fact the plant still has a lot of growing to do and the later foliage does contribute to yield.  Some other examples from the trial include:

Another thing is that rate of the fungicide makes a difference.  For example Evito at 3.1 fl oz yielded 59 bu/A while Evito at 5.7 fl oz (both R3 only applications) yielded 65.9 bu/A.

Domark  (3 fl oz/A) at R3 followed by Domark (3 fl oz/A) at R5) yield 64.9 bu/A while Domark plus Headline (3 fl oz/A) and again at R5 only yield 67.7 bu/A.

There are several things to learn from this study:

  1. If the strobilurins are effective, use them at the higher rates.  This will diminish the chances of fungicide resistance developing in the population.
  2. The triazoles are equally effective, if applied at the right rates and timings.
  3. Through the management of many, many pathogens with fungicides, it is always best to rotate classes of chemistries rather than combining them.  The only reason to combine chemistries is if you have multiple pathogens to control and you need more than one active ingredient in the tank.

Finally – the best approach to managing this disease though is to use a resistant variety; they are the same price as the susceptible and you won’t have to worry about this.


Tags: , , , , , ,


Leave a Reply

Name and Email Address are required fields. Your email will not be published or shared with third parties.

Sunbelt Ag News

    DTN Grain Midday: Trade Still Higher Across Board8-22

    Farming on the Mother Road: Change is Operative Word in New Mexico – DTN8-22

    Mississippi: Cool-Season Food Plots Benefit Wildlife, Diversity8-22

    DTN Cotton Open: Slightly Lower in Quiet Dealings8-22

    DTN Livestock Open: Hog Paper to Start Higher8-22

    DTN Grain Open: Futures Begin Quietly Higher8-22

    Keith Good: With Midwest Grain Harvest Looming, Storage Concerns Grow8-22

    Grain TV: Strong Exports, Weak Crop Tour Reports8-21

    AFB Grain-Soybean Close: Prices Bounce Off Lows to Slight Gains8-21

    AFB Cotton Close: Futures Post Small Gains8-21

    AFB Rice Close: Futures Give Back Early Week Gains8-21

    DTN Livestock Close: Lean Hog Futures Engineer Huge Reversal8-21

    Doane Cotton Close: Technical Strength Could Mark Selling Opportunity8-21

    Beef Checkoff Effort Stalls – DTN8-21

    DTN Cotton Close: Dec. Edges Higher in Mixed Trade8-21

    Farming on the Mother Road: Amarillo, Heart of Cattle Feed Country – DTN8-21

    Biofuels: Nebraska Switchgrass Cultivar Provides Promise – DTN8-21

    Louisiana: Rice Disease Field Tour, Crowley, Aug. 268-21

    Chumrau on Wheat: Large World Supply Is Certain, Quality Is the Question8-21

    DTN Grain Close: Old Crop Soybeans, Wheat Lead Markets Higher8-21

    DTN Livestock Midday: Hog Futures Rally Higher8-21

    U.S. Grain Transportation: STB Takes Steps to Resolve Rail Backlog8-21

    AgFax Rice Review: Japan Resumes Fukushima Exports; India Production Estimates Lifted8-21

    U.S. Drought Outlook: Improvement Across Southwest, California Still Dry8-21

    U.S. Energy: Midland Crude Prices Falling Below Cushing Prices8-21

    Gasoline Prices: Decrease by 3 Cents8-21

    Propane Stocks: Up 2.5M Barrels8-21

    Diesel Prices: Average Drops 1 Cent8-21

    North Carolina Soybeans: Cause of Leaf Yellowing, Curling Unknown8-21

    Texas Town Claims Oldest Working Cotton Gin – AgFax8-21

    Southeast Cotton – Late Insects Forcing Tough Decisions – AgFax8-20

    Late Soybeans Lack Heat Units, Frost Concerns in Midwest – AgFax8-20

    Farmers Work to Wrap Up Summer as Fall Peeks Over Horizon – DTN8-20

    Louisiana: Destructive Emerald Ash Borer Spreads with Firewood8-20

    The Glory Days Are Gone: Not Your Daddy’s Farm Program – DTN8-20

    Crop Insurance: Commodity Payment Caps and AGI Restrictions – DTN8-20

    Do Big Corn Crops Always Get Bigger? Not Necessarily.8-20

    AgFax Cotton Review: World Consumption to Rise; Best Texas Yields in 3 Years8-20

    Louisiana: Fertilizer Research Benefits from New Equipment8-20

    AgFax Grain Review: Longest Bear Streak in 8 Years; Watch Silage Moisture Levels8-20

    Farming on the Mother Road: Okies Still Battling Droughts — DTN8-20

    Cotton in Southwest: Resistant Pigweed Thrives: Aphids Won’t Quit – AgFax8-19

    USDA: Weekly National Peanut Prices8-19

    Farmland Prices Expected to Stabilize, Possibly Decline8-19

    Crop Insurance: Remember to Verify Acreage History at Local FSA Office8-19

    Local Crop Reports: Still Some Issues Out There — DTN8-19

    Oil Crops Outlook: U.S. Soybean Yields Rise With Favorable Weather8-19

    Cotton Outlook: U.S. Production Increased 1M Bales8-19

    GMO Critics Invited to Testify at Public Meeting on Biotech — DTN8-19

    Rice Outlook: U.S. 2014-15 Production Projected at 228.8M Cwt8-19

    Welch on Grain: Yield Prospects Continue to Look Strong8-18

    Welch on Wheat: Prices Continue to Struggle8-18

    Brazil Considers Ban on Second Crop Soybeans Due to Disease – DTN8-18

    Good on Grain: Corn and Soybean Acreage8-18

    Study: Feed Identified as Risk Factor in Spread of PEDv — DTN8-18

    Flint on Crops: Nutrient Deficiencies at Root of Many Problems8-18

    Pork Prices Rising in South Korea — DTN8-18

    Sunbelt Ag Events

     

    About Us

    AgFax.Com covers agricultural trends and production topics, with an emphasis on news about cotton, rice, peanuts, corn, soybeans, wheat and tree crops, including almonds, pecans, walnuts and pistachios.

      

    This site also serves as the on-line presence of electronic crop and pest reports published by AgFax Media LLC (formerly Looking South Communications).

        

    Click here to subscribe to our free reports.

      

    We provide early warnings and confirmations about pests, diseases and other factors that influence yield. Our goal is to quickly provide farmers and crop advisors with information needed to make better and more profitable decisions.

         

    Our free weekly crop and pest advisories include:

    • AgFax Midsouth Cotton, covering cotton production and news in Alabama, Arkansas, Louisiana, Mississippi, Tennessee and Missouri.

    • AgFax Southeast Cotton, covering cotton production and news in Alabama, Florida, Georgia, North Carolina, South Carolina and Virginia.

    • AgFax Southwest Cotton (new for 2013!), covering cotton production and news in Texas, Oklahoma, Kansas and New Mexico.

    • AgFax West (formerly MiteFax: SJV Cotton), covering California cotton, alfalfa, tomatoes and other non-permanent crops in California's Central Valley.

    • AgFax Rice covering rice production and news in Arkansas, Louisiana, Mississippi, Missouri and Texas.

    • AgFax Peanuts, covering peanut production in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas and Virginia.

    • AgFax Southern Grain: covering soybeans, corn, milo and small grains in Southern states.

    • AgFax Almonds, covering almonds, pistachios, walnuts and other tree crops in California's Central Valley.

    • AgCom 101, providing guidance to ag professionals involved in social media.

    Our newsletters are sponsored by the following companies: FMC Corporation Chemtura Dow AgroSciences.

          

    Mission statement:

    Make it as easy as possible for our community of readers to find and/or receive needed information.

              

    Contact Information:

    AgFax Media. LLC

    142 Westlake Drive Brandon, MS 39047

    601-992-9488 Office 601-992-3503 Fax

    Owen Taylor Debra L. Ferguson Laurie Courtney

          

    Circulation Questions?

    Contact Laurie Courtney