Fusiform rust is a pine tree's worst enemy. This fungus targets and weakens pine trees throughout their lifecycle. The damage caused by these fungi often leads to the loss of the tree and costly damage if the tree falls. Being able to identify fusiform rust may save your tree and prevent expensive repairs. 

1.) What Causes Fusiform Rust

The fungus Cronartium quercuum causes fusiform rust and affects both oak trees and pine trees during their lifecycle. This fungus forms by growing in its most early stages on oak trees, but the fungus transfers to pine trees as it progresses through its life stages. 

These fungal spores spread by wind and may drift miles until they find an acceptable host. Spores spread from infected oaks to pines during warm, balmy conditions — typically in late spring and summer.

2.) How Fusiform Rust Affects Trees

Fusiform rust affects pine trees and oak trees differently. These fungi spend their time growing on the leaves of oak trees. The fungi usually present themselves as orange spots on oak leaves, though once the fungi are close to releasing their spores, it makes the oak leaves fuzzy or hairy in appearance. 

Once the spores transfer from oak trees to pine trees, galls begin to form. Galls look like long, cigar-shaped cankers. Sometimes these cankers appear as if the pine tree has been struck by lightning and split the tree. Early infections look like part of the pine has been coated in artificial cheese dust. These bright, orange spores are where fusiform rust gets its name. 

This fungus attacks the stems of pine trees, including the trunk. As the galls grow, the site of the gall becomes warped and weakened. Galls may be only several inches long but can grow to be a foot or more in length.

3.) Fusiform Rust Is Fatal to Trees

Fusiform rust is fatal to pine trees over time. There isn't currently a fungal treatment on the market that can heal a tree infected with fusiform rust once the infection has progressed. Trees infected with this fungus are very susceptible to wind damage and are prone to falling in storms.  

The most vulnerable pine trees are those with infected trunks. You should have pine trees with infected trunks removed, especially if they are near a building. Typically after several years of infection, a pine tree will have to be culled. 

If you suspect fusiform rust has infected your trees, contact a local tree service like Pete & Ron's Tree Service, Inc. to remove the infected trees.