 The most important factor when it comes to getting good fungicide performance is simply spraying before you see a disease outbreak. Fungicides are great at preventing disease, but they can't help you recover yield that's already been lost once you see disease in your crop. So spray early. That's the key. Of course, you've got to pick a fungicide that actually works. For example, you don't want to spray headline on soybeans if you're after sclerotinia white mold.