Common Fungal Diseases of Trees and Shrubs

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Dutch Elm Disease is a vascular wilt fungal disease that affects American elm trees. This fungal infection clogs the vascular tissue, which prevents water and nutrient movement to the crown of the tree and appears as flagging, or wilted leaves throughout the canopy. 

Fire blight is a bacterial disease that affects plants in the rose family and will appear as scorching or burnt and blackened foliage and shoots creating a "shepherd's crook". This disease is spread in the spring by wind, rain, and insects.

Apple scab is fungal disease that infects primarily apples and crab apples, but also other plants in the rose family. This disease affects the leaves and fruit. The spores overwinter mostly on the fallen leaves, and fruit which then re-infect the host in the spring. 

Diplodia Tip Blight is a fungal disease that affects Pine species, mainly Austrian pine. The affected needles will appear stunted in comparison to healthy needles, and will remain on the tree for many years. This fungal disease is spread by wind, rain splash, insects, and infected tools. Severe infections can lead to the death of the tree. 

Oak Wilt is a fungal disease that interrupts the vascular system, producing wilting and death. Disease severity varies depending on oak species and region. Red oaks are the most vulnerable and usually die within one year, while damage in white oaks progresses more slowly. 

Powdery Mildew is a very common fungal disease that can appear on a large variety of trees and shrubs. It appears as threadlike white patches, as if the plant was dusted with powder. This disease thrives in an environment with warm days, cool nights, and high humidity. The spores are vectored by wind currents.