Melamspora leaf rust

Melamspora medusa

Hosts

Poplar, willow

Distribution and Disease Cycle

Description of this image follows
Poplar leaf infected with Melamspora leaf rust.
Photo credit: Agroforestry Development Centre

Melamspora leaf rust is caused by a fungal pathogen that requires two different hosts to complete its life cycle (either poplar or willow as one host and larch or a few other coniferous hosts as the other). In spring, basiodiospores are released from overwintering structures on fallen poplar or willow leaves, infecting nearby larch or a few other specific conifer hosts. Later that season, a different type of spore (termed aeciospores) are produced on infected larch/conifers capable of reinfecting poplar or willow. A 3rd type of spore (urediospore) produced on newly infected poplar/willow can then spread and infect other poplar/willow. In fall, structures are produced on infected poplar/willow leaves allowing the pathogen to overwinter and repeat the cycle the following spring. Infection leads to premature leaf drop and potentially loss of vigor leading to decline in some trees.

Symptoms and signs

Description of this image follows
Melampsora leaf rust on hybrid poplar.
Photo credit: Agroforestry Development Centre

Infection results in masses of conspicuous orange-yellow spores (the urediospores) on poplar or willow leaf surfaces. Infections can cause premature leaf drop in late summer resulting in loss of vigor in host trees, with repeat infections possibly leading to decline of susceptible trees. The larch/conifer alternate host is not significantly impacted by infection, thus do not present with any notable symptoms.

Control

Clean up fallen leaves to reduce inoculum. Use resistant selec-tions or plant a mix of selctions with varying susceptibility to different strains of the fungus.

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