Mycosphaerella macrospora, formerly known as Didymellina macrospora, is the leading fungus on iris plants. This fungus causes leaf spots, which look like small brown spots with a yellowish halo on the top portion of the leaves. The fungus starts out slow, but as temperature increases so do the number of spots. Use a fungicide that names this specific fungus to ensure plant health.
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Living in Southern California, Shayne Ochoa has been writing professionally since 2005. Her articles have included topics on education, child development and gardening. She also holds a Bachelor of Arts degree in liberal studies from California Baptist University in Riverside.