Rusts are diseases caused by a complex group of fungi. The fungi produce spores in pustules that break through the plant epidermis. The spores are generally reddish brown, orange red to orange, and dry and dusty. Many plants, from grasses to pine trees, get rust diseases. A common experience is to walk through tall grass infected with rust and emerge with shoes coated in orange-red spores.
The rust diseases produce several different spores, each spore capable of infecting a different plant. The cedar-apple rusts are a good example. Spores formed in galls on cedar infect apple leaves, causing leaf spots. Spores formed on apple leaves infect only the cedar needles, causing galls. Rusts generally infect healthy, vigorous plants in preference to weak plants.
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|White pine blister rust - 40K||White pine blister rust, mature canker - 48K|
|White pine blister rust, twig swellings - 33K||White pine blister rust on gooseberry - 30K|
|White pine blister rust - 24K||White pine blister rust - 42K|