I'm currently using "Neem oil" as a fungicide/insectacide for my peaches in the early spring and throughout the growing season. Are there more effective products for treating my trees organically?
Early Spring Sprays Peach Trees
Certified GKH Gardening Expert
In terms of organic, neem is considered to be one of the best because it is both a fungicide and an insecticide and one of the few insecticides that will not harm bees.
You can also try citrus oil. It is generally considered not to be as effective, but does treat both. You can also look for sprays that combine both neem and citrus for a little extra oomph.