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Evaluating Headline Fungicide on Alfalfa Production and Sensitivity of Pathogens to Pyraclostrobin

Deborah A. Samac, Bill Halfman, Bryan Jensen, Fritz Brietenbach, Lisa Behnken, Jaime Willbur, Daniel Undersander, Greg Blonde, JoAnn F. S. Lamb
Plant health progress 2013 v.14 no.1 pp. -
Medicago sativa, Phoma medicaginis, Stemphylium, active ingredients, crude protein, defoliation, developmental stages, disease control, field experimentation, foliar diseases, forage quality, forage yield, fungal diseases of plants, insecticides, pathogens, pesticide application, pyraclostrobin, Minnesota, Wisconsin
Headline fungicide was recently registered for management of foliar diseases on alfalfa. The effect of disease control on yield, forage quality, and potential return on investment for fungicide application was determined for field experiments conducted at five locations in 2012, three in Wisconsin and two in Minnesota. Headline reduced defoliation in 12 out of 14 harvests and increased forage yield and return on investment in 5 out 12 harvests compared to the untreated control. Headline plus the insecticide Warrior II reduced defoliation in 10 out of 14 harvests and increased yield and return on investment in four harvests compared to Warrior II alone. Two common foliar pathogens were highly sensitive to pyraclostrobin, the active ingredient in Headline. For Phoma medicaginis, the in vitro EC₅₀ was 2.3 ng pyraclostrobin/ml and for Stemphylium globuliferum the EC₅₀ was 52 ng pyraclostrobin/ml. The results indicate that fungicide application can increase yields under higher disease pressure and increase crude protein when the crop is harvested at later developmental stages.