Rusts are fungal diseases that infect many hosts, including birch, cottonwood, cypress, false cypress,
fuchsia, hawthorn, juniper, pine, poplar, rhododendron, rose, and spruce. Dry reddish, yellowish, or orange
spore masses or pustules form on infected tissue, especially on the lower surface of leaves. The upper
surface of heavily infested leaves turns yellow or brown and infected leaves may drop prematurely. Orange,
gelatinous masses appear on some infected evergreen hosts. Some species cause tissue swellings or galls,
colorful spots on plants, or cankers on bark. These can cause branch dieback and occasionally kill the
entire plant. Some rusts may cause leaves and shoots to become distorted, dwarfed, and discolored, forming
Avoid overhead watering, which favors spore
germination. Rake infected leaves or needles and clip and
dispose of infected shoots and branches as soon as they appear.
Fungicides applied in the spring can reduce
some rust diseases, but the frequent applications required
to provide good control are generally not warranted in landscapes.
To control white pine blister rust, nearby alternate
hosts (Ribes spp.) are sometimes removed, but the effectiveness of this is questionable.
spores on rose leaves
western gall rust swellings