Update on Foliar Fungicides on Corn and Soybean

1. Update on Foliar Fungicides on Corn and Soybean P. Vincelli, C. Lee, and D. Hershman University of Kentucky

2. Strobilurin fungicides labeled for corn and soybean • Headline (pyraclostrobin): Corn and soybean • Quadris (azoxystrobin): Corn and soybean • Quadris Xtra (+ cyproconazole): Soybean (section 18 for SBR). • Quilt (premix of azoxystrobin and propiconazole): Corn and soybean (section 18 for SBR) • Stratego (premix of trifloxystrobin and propiconazole): Corn and soybean • Several triazoles available but not thoroughly tested in either corn or soybean

3. For which corn diseases? Northern leaf blight Gray leaf spot Image by K. Leonard and E. G. Suggs Courtesy of the American Phytopathological Society Both survive in infested corn residue.

4. For which diseases (cont’d)? Common rust: usually minor to no effect on yield Southern rust: damaging but very sporadic

5. For which soybean diseases? Brown Spot Pod and Stem Blight/Anthracnose

6. For which soybean diseases? Cercospora Leaf Blight Frogeye Leafspot

7. Strobilurin fungicides provide excellent disease control in both corn and soybean. Yields are higher when disease levels are sufficient to reduce yield in untreated crops.

8. Yield differential in corn from a strobilurin fungicide application in 68 university research trials through 2006 Yield difference, trt minus untrt (bu/A) Some trials conducted with susceptible hybrids or other conditions expected to increase disease pressure. Data collated by Pioneer Hi-Bred.

9. 40.5% 59.5% Compiled by Arv Grybauskas and Liz Reed, UMD 2006 Soybean – 74 Headline Trials in Northern U.S. 20.0 Mean = + 2.8 bu/A n = 74 15.0 P > 0.05 P ≤ 0.05 10.0 Average Yield Response to Headline (bu/A) 5.0 0.0 IL, Tams Delaware MO, Alma OH, Ross WI, Bristol ND, Fargo OH, Wood OH, Henry SD, Groton OH, Hardin OH, Shelby WI, Wood 2 WI, Wood 1 ON, Harrow WI, Green 1 OH, Fayette WI, Green 2 NE, SCAL 1 NE, ARDC 1 IN, Davis (L) NY, Waterloo IL, Brookport IN, Davis (S) MN, Waseca MO, Dockery KY, Princeton WI, Columbia IN, Pinney (L) IN, Pinney (S) WI, Stoughton IN, SEPAC (L) MO, Henrietta IN, NEPAC (L) SD, Brookings IN, NEPAC (S) MI, Saginaw B MI, Saginaw S IN, SEPAC (S) WI, Arlington C WI, Arlington N ND, Colfax (L) MO, Hundley 3 NE, Tekamah 1 SD, Watertown MO, Hundley 2 MO, Richmond ND, Colfax (S) MO, Bradford 4 MO, Bradford 1 MN, Lamberton MO, Bradford 3 MO, Henrietta II MD, Beltsville C MI, Saginaw C6 MI, Saginaw C2 MO, Greenley 4 KY, Madisonville IA, Saratoga R2 MO, Greenley 3 MO, Greenley 1 MD, Beltsville N IA, Saratoga R4 MO, Higginsville MD, Keedysville MO, Henrietta III NY, Seneca Falls MO, Richmond II IN, Throckmorton (L) MD, Queenstown (L) IN, Throckmorton (S) MD, Queenstown (IR) MD, Queenstown (S) N MO, Hundley-Whaley 1 MD, Queenstown (S) C -5.0 -10.0 Location

10. Is there a yield benefit from strobilurin fungicide on corn that goes beyond disease control? Test this by evaluating yield in the absence of disease

11. Hybrids selected for 2007 trials †All ratings were provided by the company. 1-2 = Excellent, 3-4 = Very Good, 5-6 = Good, 7-8 = Fair, 9 = Poor

12. Key information on 2007 trials

13. Logan County results, 2007

14. Spindletop Farm results, 2007

15. Is there a yield benefit from strobilurin fungicide on corn that goes beyond disease control? To date, most research at UK and beyond does not support this notion

16. Variability of Results is a Concern • Farm “C”, Field 1, Soybean Test, Henderson KY • 2005 • Response of 28 strips (24 varieties): • Mean = +10.2 bu/A • Range = 3.3 – 20.3 bu • Response of 5 “tester” strips (CPS 6444NRR): • Mean = 13.4 bu • Range = 9.7 – 18.9 bu

17. Variability of Results is a Concern • Farm “C”, Field 1, Soybean Test, Henderson KY • 2005 • Response of 28 strips (24 varieties): • Mean = +10.2 bu/A • Range = 3.3 – 20.3 bu • Response of 5 “tester” strips (CPS 6444NRR): • Mean = 13.4 bu • Range = 9.7 – 18.9 bu • 2007 • Response of 30 strips (26 varieties): • Mean = +3.6 bu/A • Range = -0.5 – 10.4 bu • Response of 5 “tester” strips (Vigoro V44N6RR): • Mean = 3.6 bu • Range = 1.3 – 8.7 bu

18. Economic Variability • Assume: $22 for fungicide and application • Breakeven: • $9.50 soybeans = 2.3 bu/A • $8.50 soybeans = 2.6 bu • $7.50 soybeans = 2.9 bu • $6.50 soybeans = 3.4 bu • $5.50 soybeans = 4.0 bu • 2005 (Henderson County Example) • Mean, 10.3 bu; Range 3.3 bu – 20.3 • 2007 • Mean, 3.6 bu; Range 1.3 - 8.7 (40 % of strips below 2.5 bu response)

19. Conclusion • Fungicides (primarily strobilurins) do increase yield when diseases are yield-limiting. • Expect less than stellar results when disease is not limiting yield. • Apply fungicides to corn or soybean when the probability of a response is greatest. • Avoid applying fungicides when the potential for a response is low.

20. 2nd year corn or soybean No-till Susceptible hybrid (corn) Late planting (corn), early planting, early maturity (soybean) High yield potential Disease activity at tasseling (corn), beginning pod (soybean) Disease-favorable weather or crop irrigated Climbing the “Probability Ladder”: Factors that increase the probability of yield response from fungicides on corn and soybean Higher probability Lower probability

21. Public concern is a concern • Acres of corn and soybean sprayed in Kentucky • 2000 • Corn: <1% • Soybean: <1% • 2007 • Corn: 20% • Soybean : 25% • Most of KY’s and U.S. population is no longer rural and the public generally fears use of pesticides by farmers. • “Plant Health” application of fungicides has gotten EPA’s attention.