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SOYBEAN FUNGICIDES

SOYBEAN FUNGICIDES. Situation: In 2003, Syngenta began encouraging growers to apply Quadris (strobilurin fungicide) and Warrior (synthetic pyrethroid insecticide ) to reproductive soybean as a means of increasing yield, but without any evidence of pest problems.

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SOYBEAN FUNGICIDES

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  1. SOYBEAN FUNGICIDES • Situation: In 2003, Syngenta began encouraging growers to apply Quadris (strobilurin fungicide) and Warrior (synthetic pyrethroid insecticide ) to reproductive soybean as a means of increasing yield, but without any evidence of pest problems. • In KY, about 20,000 acres were treated in 2003 and 60,000 acres in 2004. • Headline (a strobilurin) was labeled in early 2005 and well over 100,000 acres were treated in KY this year. Very little Quadris was applied because of higher cost compared with Headline and aggressive marketing by BASF and SBR scare. • Use spread throughout the North Central region in 2005. • BASF pushed use for “plant health” and SBR “insurance”. Also used subtle scare tactics to sell Headline SBR (Headline + Folicur).

  2. Subtle(?) scare tactics used to sell Headline SBR in KY in 2005

  3. Fungicide Applications for Soybean “Plant Health” • Defined as fungicide (strobilurin) use in soybean where target diseases are not defined. • Applications are to encourage overall “plant health”. • Application target is R3 stage (beginning pod). • Based on the assumption that full yield potential is rarely, if ever, realized in modern cropping systems. • Yield potential lost due to: • Crop stresses and inefficiencies (non-optimal temperature, nutrients, soil water, weeds, insects, etc) • Diseases (ranging from hidden (background) levels to obviously damaging)

  4. Strobilurin Effects in Soybean • Stress-reducing physiological effects. • Increased rate of photosynthesis • Decreased respiration and ethylene biosynthesis • Activation of non-specific plant defense mechanisms (e.g., H202) • Improved nitrogen assimilation • Treated plants better able to deal with light to moderate stress conditions. • Limited value when growing conditions are good or when stress conditions severe.

  5. Strobilurin Effects in Soybean • Controls some common fungal diseases. • Brown spot • Frog eye leaf spot • Stem anthracnose • Complexes of the above diseases, especially when present at low (background) levels. • Does not control: • Any common viral, bacterial, or nematode diseases. • Many common (and damaging) fungal diseases. • Charcoal rot • Sudden death syndrome • Stem canker • Pod and stem blight; pod anthracnose • Cercospora leaf blight

  6. Strobilurin Yield Effects in Soybean • Yield response to strobilurin chemistry variable. • Ranges from no apparent yield advantage to as high as 20+ bu/a • Non-replicated, on-farm strip tests; replicated strip tests, replicated small plot studies in KY, and a host of North Central States (IA, IN, IL, MO. MN, WI, ND, SD, OH) all show a range of results from no effect to 20+ bu/A (with no obvious disease controlled!) • Deep southern states have used fungicides for years due to consistently higher late-season disease pressure (especially frogeye leaf spot). • KY response more in line with North Central Region than deep south.

  7. 2003-05 KY ON-FARM STRIP PLOT COMPARISONS treatment breakeven 3-4 bu/A *Difference treated – non treated, 2003, 2004 mostly treated with 6.2 fl oz Quadris + 2.56 fl oz Warrior/A. 2005 primarily treated with Headline at 6.0 fl oz.

  8. Reasons for Variable Response • Crops under varying degrees of stress. • Good response: • Moderate stress (environment and/or pathogens sensitive to strobilurin) • Poor response • Little crop stress • Overwhelming stress • Due to environment and/or other pests not impacted by strobilurin chemistry

  9. 2003-05 KY ON-FARM STRIP PLOT COMPARISONS treatment breakeven 3-4 bu/A

  10. Reasons for Variable Response • Yield/Stress variation by region.

  11. More Reasons for Variable Response • Variable application timing.

  12. More Reasons for Variable Response • Variable application and equipment technique. • Improper droplet size • Improper spray pressure • Improper spay gallonage • Results in differential coverage within canopy • Variable levels of a.i. taken up by the plant means variable crop response to stress/disease. • Different varieties planted • Non-adapted varieties planted in some fields, adapted in some, and some marginal for area. • Variable stress response in similar environment

  13. RECOMMENDATIONS • Useful in fields that have a history of crop stress. • Useful in fields planted to marginally-adapted varieties • Question use in high productivity fields with excellent production history. • Use will always carry risk of no economic effect due to lack of stresses or overwhelming stresses. • Any field may benefit in any given year, but no way at present to predict this. • Caution: Insect populations may flair due to off-target kill of common entomopathic fungi (problems with flaring looper, aphid, and mite populations were noted some fields in 2005).

  14. SOYBEAN RUST UPDATE • Detected in 136 counties; sentinel network very effective. • First confirmation: FL on Feb 23 • Most recent confirmations: KY (Whitfield County, GA, kudzu) on Nov 21. • Detection peaks in Aug (38 new finds) and Oct (56 new finds) • Most soybean detections made in the R5-R8 stages. None before R3. • Most detections evident in hot spots and not uniformly distributed in sentinel plots or crops. • Soybean appears to be much more susceptible than kudzu; main importance is as an overwintering host and not as a source of spores during the growing season. • Not found on any other legumes except FL Beggarweed. • Sentinel plot numbers will be lower in 2006, but much more emphasis will be placed on microscopic observation as opposed to relying on field scouting.

  15. SOYBEAN RUST UPDATE • Chances for greater overwintering populations this winter much higher than last: • Heavily infected kudzu present at this time in southern AL, GA, and TX. • Announcement may soon be made that SBR has been detected in Mexico (unofficial at this time). • The Texas/Mexican finds significantly alter the situation for 2006; greater potential for movement along the “Puccinia pathway” (TX > MN; TX > Ohio River Valley) • Weather will ultimately determine what happens. 2005 was an unusually dry year in the deep south in spite of all the hurricane activity.

  16. Disease Progress Information • Takes about 2 months to defoliate a crop following initial detection. • 1-month lag phase where disease gets established and builds up in lower canopy. • 1-month explosive phase where disease progressively moves into and eventually defoliates the mid and later upper crop canopy. • Very “well behaved” disease. Data: Jim Marois, Univ.of FL, Quincy Data based on observations in ten Florida sentinel plots

  17. SBR FUNGICIDES • Good tests in Florida and Georgia. • Section 18 products performed very well when applied twice. • Single applications were iffy unless infections came in late (R5-ish). • 20+ bu/A yield differences seen in tests and growers fields in GA where fungicides were applied (compared with non-treated).

  18. Aerial View of SBR Fungicide TestAttapulgus, GA* Source: Bob Kemerait, University of GA *Attpulgis is in far southwest GA, very near the Florida line.

  19. A A AB AB CD F B C-F F C-F ATTAPULGUS, Southwest GA Data source: Bob Kemerait, UG

  20. Greener Longer…. “Headline SBR”

  21. Lessons for Growers from 2005 • Growers can effectively manage rust with fungicides. • However, the disease seems unforgiving to mistakes. • First spray is more CRITICAL than second spray. Make it count! • Early reproductive growth seems appropriate for 1st spray IF rust appears.. • Difficult to say what is “best”, but Folicur, Headline SBR, and Domark look very good. • Laredo, Sparta, Quilt, Headline, Quadris and Stratego effective, but ranking to above unclear. • Role of chlorothalonil (Echo, Bravo) in rust management is questionable.

  22. RISK MANAGEMENT AGENCY-SPONSORED SOYBEAN RUST CROP INSURANCE MEETING: 9 am – noon (ends with meal) January 17, 2006 * UKREC, Princeton * Remote location, Hardin County Extension Office

  23. Wheat Update • Probably will not seek a Folicur section 18 for FHB control in 2006. • Had great difficulty getting it in 2005 • No FHB in 2005, excellent yields and grain quality, and the availability of propiconazole (Bumper, PropiMax, Tilt) for late, pre-flowering applications, make it very unlikely we would be approved in 2006. • Stripe Rust • New race has developed that overwinters in Mexico. • Will probably be dealing with this disease now on a regular basis. • Good resistance available and the ratings can be seen in the UK Small Grain variety test pub. • All modern wheat fungicides do a very good job controlling stripe rust (tilt, folicur, quilt, headline, quadris)

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