The Order Uredinales, or rusts, are among the most important of the Basidiomycetes. There are about 4000-6000 species of rusts, all of which are plant parasites requiring at least one plant as a host to complete its lifecycle. They attack more types of wild and domesticated plants than any other natural fungus. They have a complex lifecycle, having five different spore types including basidiospores, pycniospores, aeciospores, teliospores, and urediospores (the most common one found). It is a type I allergen, and not a known toxin producer. Rusts produce red or rusty to orange spores. They can be found on trees, flowers, grasses, and other living plant materials. Very rarely found growing indoors, unless their host plants are present. Culture – Not recommended. Microscopy of spores provides tentative identification.