Tree rusts are fungal diseases causing dusty orange or brown spots (pustules) on the leaves of poplar, willow, birch, plum and five-needled pine.
Tree rusts cause eye-catching infections on the leaves of some trees, particularly Populus spp. (poplar), Salix spp. (willow), Betula spp. (birch), plum and Pinus spp. (five-needled pines). Tree rusts may be seen from spring until autumn for trees that lose their leaves in winter (deciduous) and all year on evergreens.
These are the rust fungi involved:
> Poplar rust is caused by several species of Melampsora
> Willow rust is also caused by several species of Melampsora, but not the same as those infecting poplars
> Birch rust is caused by Melampsoridium betulinumPlum rust is caused by Tranzschelia pruni-spinosae var. discolor
> Five-needled pines are infected by white pine blister rust, caused by Cronartium ribicola
Via Plant-Microbe Interaction