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FUNGAL DISEASES THAT ARE EASY TO IDENTIFY

Like powdery mildews, rusts (rose rust is shown in this photo) are easily identified by eye. The rusty-orange, powdery PUSTULES (see arrow) that are produced by rusts are distinct and characteristic. The spores of rust fungi are easily removed from the leaf surface by gentle rubbing.

Rust fungi are particularly incredible fungi. In addition to their typically orange spores (called urediospores), these fungi can produce up to four additional, distinct spore types. In addition, some rusts have alternate hosts, spending some of their life cycle on one host and the rest on a second host. A classic example is the cedar-apple rust fungus, which spends a portion of its life cycle on red cedar, the rest on apple. Between the two hosts this rust fungus produces four different types of spores.