Melampsora amygdalinae is a fungal pathogen and part of the division Basidiomycota. It is known as a rust fungus that is host specific. M. amygdalinae commonly infects willows of the genus Salix. This fungus was first discovered in 1909 by Heinrich Klebahn who was a professor of soil biology in Hamburg. Neimi at el. explain how the pathogen occurs throughout the whole distribution of the host, and the small natural populations are an area of interest. This rust fungus is annual (non systemic) and autoecious, which references the fungus spending its entire life in a single host. Hosts and symptoms Willows are a highly susceptible host that this pathogen targets. Fungicides are not usually used for its protection, as the result is not effective. The fungicides needed for this rust fungus would also affect the surrounding environment. “Several studies reported very low differentiation among samples of fungal pathogens of agricultural crops or forestry trees from different localities across a continent.” To further explain, this shows that this fungus affects its host similarly across the continent. The environment and location of the fungus does not differentiate its functionality. Symptoms that appear on willows are commonly seen as galls. M. amygdalinae distorts the blades and veins of willow, causing irregular spots, bearing the orange yellow uredinia, which is the lesion that forms on the leaf surface. Pustules are what the lesion is referred to as. “The host range and pathogenicity of these species have remained static as no breakdown in host resistance has been observed”. To expand, the host plant has yet to show signs of resistance, only emphasizing the evidence of its susceptibility. This pathogen lacks telia and tends to overwinter in its specific host. The pathogen and the host have the ability to reproduce sexually and are both locally adapted to each other. Disease cycle The life cycle of M. amygdalinae is macrocyclic, or has all spore states in its life cycle, which is important to know when trying to perform any disease management. In the spring it undergoes sexual reproduction and the teliospores germinate after overwintering, then produce basidia. The basidia then release basidiospores that travel through the wind to infect the host plant. The host is infected by the haploid basidiospores that form spermagonia. “After dikaryotization by transfer of spermatia to the receiving structures of compatible mating types, aecia are formed. From these, aecidiospores are dispersed, which, after