Rust spores

Rust fungi are obligate plant pathogens that can cause severe disease on many plant species. Two types of rust spores, uredospores (urediniospores) and teliospores are commonly seen on air samples. Although additional spore types are produced by some rust species, they may not be recognizable in air samples. See Rust fungi for additional information. 

Both uredospores and teliospores are large and range from 20–40 µm in length. The uredospores are a single-celled and may be colorless or lightly pigmented. The teliospores are more deeply pigmented with one cell, two cells, or several cells and a thicker wall.