White Rust of Crucifers
A. candida belongs to the phylum Oomycetes (the phylum that also includes the downy mildews and water molds). These molds produce both fertilized and asexual spores. The asexual spores (zoospores) have two whip-like flagella that enable them to move about. Infections from these spores appear as pustules or blisters. The fertilized spores (oospores) grow inside the plant tissues and cause abnormal growths, called stagheads.