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Disease Information

Plant Diseases

Disease fungi take their energy from the plants on which they live. They are responsible for a great deal of damage and are characterized by wilting, scabs, moldy coatings, rusts, blotches and rotted tissue.

Healthy soils and correct growing conditions are the best ways to prevent many plant problems from occurring.

 

This page is designed to help identify some of the more common plant diseases.

White Pine Blister Rust - Cronartium ribicola

Cronartium ribicola is a species of rust fungus in the family Cronartiaceae that causes the disease white pine blister rust.

Cronartium ribicola is native to China, and was subsequently introduced to North America via contimated Blacurrant plants during the 1900's.

 

Some European and Asian white pines (e.g. Macedonian Pine, Swiss Pine, Blue Pine) are mostly resistant to the disease, having co-evolved with the pathogen.

Some limited silvicultural control of the disease is possible. If bark blisters are found on branches over 10–15 cm from the bole, those branches may be pruned off, which will stop the spread of the disease to the rest of that tree. If the main trunk is affected then no control is possible, and the tree will die once the infection encircles the tree.

Whit Pine Blister Rust
White Pine Blister Rust

Infected trees are often identified by "flagging", when all the needles on a branch turn brown and die. Infections often occur on low branches close to the ground on young trees, so pruning of white pine can also be effective in multiple ways, as it improves the quality of timber by creating more knot-free timber, and reduces the likelihood of infection from the blister rust to a small extent.

 

Another form of control practiced in some areas is to diligently remove Ribes plants from any area near white pines.

Because the infection moves from Ribes (currant) plants, to pines, and back again, it cannot continue to exist without its alternate host.

Leaf

Although effective in theory, removal of currants is rarely successful in practice, as they readily re-grow from small pieces of root left in the soil, and the seeds are very widely spread in birds' droppings.

 

White pine blister rust attacks all five needle pines. Plant damage includes mortality, top kill, branch dieback, and predisposition to attack by other agents, including bark beetles.

White pine blister - Cronartium ribicola on Ribes leaf

White Pine Blister Rust

White pine blister - Cronartium ribicola pathogen

White Pine Blister Rust

White pine blister - Cronartium ribicola killing pine needles

White Pine Blister Rust

Cronartium ribicola infected needles