Lehtirungosten

Lehtirungosten is a Finnish term used in forestry and plant pathology to refer to rust diseases that affect both leaves (lehti) and stems/trunks (rungot). The term does not denote a single pathogen but a group of rust fungi within the order Pucciniales. These fungi produce characteristic orange to yellowish pustules on the lower leaf surfaces and can also cause lesions on shoots and stems. Many rust fungi are heteroecious, requiring alternate host species to complete their life cycles, with complex stages including basidiospores, urediniospores, and teliospores. In Nordic climates, lehtirungosten commonly affect species such as birch, willow, alder, and other deciduous trees; outbreaks are favored by wet springs and mild summers. Economic impacts include reduced photosynthetic capacity, growth loss, and aesthetic damage in ornamental plantings.

Diagnosis is based on symptom observation and microscopic identification of spores; management focuses on preventing spread and maintaining plant health; practices include removal of heavily infected material, promoting air circulation, choosing resistant cultivars, and, where appropriate, targeted fungicide applications in nurseries or high-value trees. Because rust fungi have alternate hosts, management can also involve removing or protecting one host to disrupt the life cycle, though this is not always feasible in natural forests.

See also: rust (fungus), Pucciniales, plant pathology, forestry management.