Apioplagiostoma populi

Crops Affected: Swedish Columnar Aspen, tower poplar, poplar hybrid clones

Disease Cycle:

• Fungal pathogen
• Spores are released from mature perithecia (spore-producing structures that develop on overwintered leaves)
  • Rain and moderate to warm temperatures (18°C) trigger spore dispersal
  • Spores are spread during the spring, infecting leaves on the same tree, as well as other, adjacent trees
• In addition to being spread by spores, infections will also spread internally (systemically) to other parts of the tree
• The disease may also be spread during propagation of infected plant material
• The disease will develop over the course of the summer

Symptoms / Conditions favouring development:

• Symptoms typically appear in late summer (early-mid August) or early fall (September)
  • The appearance of symptoms is very sudden and distinct
  • Areas of the plant (often individual branches or a few leaves) will suddenly exhibit symptoms
• Symptomatic areas can be spread around the tree (not limited to a single area)
• Key Symptoms:
  • Leaf tissues turn orange-brown to reddish-brown, starting from the edges of the leaf, moving inward towards the base of the leaf
  • Leaf veins and leaf petiole (stalk) remain a bright green colour
• All leaves on a branch may be affected
• The leaf discolouration deepens to a bronzy, reddish-brown colour as the season progresses
• Infected leaves will often remain attached to the tree over the course of the winter (they do not fall off)
  • Leaves that overwinter may have a pebbly surface texture (like the surface of a curling rink), reflecting the development of spore-producing structures (perithecia)
• Branches may dieback as the disease progresses systemically

Management:

• No chemicals are registered for the management of this disease
• Avoid planting highly susceptible types in areas where disease is present
• Sanitation is the main management practice
  • Remove and destroy fallen leaves
  • Prune off infected branches back to healthy wood
    • In the case of most susceptible poplar and aspen hybrids, this means back to the trunk
    • Destroy infected branches
• Avoid planting trees species too close together

• • This improves air flow and reduces leaf debris accumulation
  • Increased density will increase humidity and potential ease of spore transfer
• Canopy density should also be kept open, to allow good air movement
• Remove infected trees
• Avoid propagating from infected material
• Ensure plants have sufficient light, moisture and nutrients