Poplar witch’s broom virus

The causative agent of the disease is Emaravirus populi, a plant virus that specifically targets trees of the Populus genus. The virus is predominantly transmitted by the eriophyid gall mite Aceria populi. As the mite feeds on the plant, it introduces viral particles into the vascular system, establishing a systemic infection that persists throughout the host's life.

The disease affects various poplar species, including black poplar and eastern cottonwood. The virus is widely distributed in regions where these trees are planted for urban landscaping, windbreaks, or timber production. The epidemiology of the disease is closely linked to the lifecycle and population density of the mite vector, which thrives in humid conditions.

The most characteristic symptom of the disease is the formation of "witches' brooms." These are dense, disordered clusters of stunted branches with shortened internodes and deformed foliage. The growth pattern is caused by the virus disrupting the tree's hormonal regulation, forcing dormant buds to sprout prematurely and develop abnormally.

• Development of dense, twiggy clusters on branches.
• Reduced vigor and stunted leaf growth.
• Lowered resistance to cold and environmental stress.
• Increased susceptibility to secondary pests and fungal infections.

The damage caused by the virus is significant as it weakens the overall health of the tree. The infected branches serve as metabolic sinks, consuming stored nutrients without contributing effectively to the tree's growth. Over time, this leads to chronic decline, reduction of aesthetic value in urban areas, and potential tree mortality during periods of severe drought or infestation.

Management and prevention focus primarily on mechanical removal and vector control. Pruning and destroying infected branches in late autumn or winter helps reduce the viral load in the canopy. Controlling the population of Aceria populi using appropriate acaricides can curb the spread during the growing season. The most sustainable long-term solution is the use of virus-resistant poplar cultivars in new plantations.