The Spread of Whitepine Blister Rust

Ontario’s provincial tree, the Eastern White Pine, has a fascinating history. This magnificent tree grew prolifically throughout eastern North America in the 1700’s and was a valued resource to the ship and furniture building industries. Whole virgin forests of white pine grew to heights of more than 150 feet (30 meters) and 20 feet (6 meters) around. This made them perfect as masts for Britain’s Royal Navy, and their strong, light wood also made excellent furniture.

The commercial value of Eastern White Pine was one of the contributing factors to the American Revolution in 1776. The Royal Navy claimed many of the trees as a property of the crown and imposed fines and floggings on anyone caught chopping them down. Just like the Boston Tea Party, colonists often disguised themselves as Indians to avoid being identified when cutting the trees for their own use.

Eastern White Pine seedlings were taken to Europe in the 1700’s to see if they could be grown closer to the British shipyards and over-harvesting of the trees in North America continued right into the 1900’s. After the clearing of almost all the Eastern White Pine here, the U.S. government decided it needed to replenish the forests. With not enough local seedlings, in the early 1900’s it imported seedlings from Europe unaware that these were infected with white pine blister rust. A massive reforestation project spread these infected seedlings throughout the eastern U.S.A. In 1910, similarly infected seedlings were imported through Vancouver, BC and the disease started its spread through the Western White Pine forests.

White pine blister rust is a disease that attacks pine trees through their needles. Five needle pines like the Eastern White Pine, Limber Pine, and Western White Pine are particularly susceptible to this disease. The spread of the disease is complex and requires two hosts. It does not spread from pine to pine but instead spreads from pine to currant plants in the spring then from currant plants to pines in the fall. The airborne spores can travel many kilometers so the disease is not confined to areas where currants and pines grow in close proximity.

Once the disease and its connection to currant plants were discovered around 1920, the U.S. government decided to fight it by exterminating currant plants. There was a ban on cultivating currants and many men were employed during the depression in a futile effort to try and exterminate wild currants. In Canada, the currant was often valued more than the pine and similar bans and extermination efforts were not put in place.

When the disease enters the pine needle, it starts to work its way back through the branches to the trunk where it will eventually cut off the flow of nutrients to the rest of the tree. If caught early, it is possible to prune the infected branches and save the tree but this is not practical in the wilderness. Younger, smaller trees can be quickly killed by the disease.

Today, white pine blister rust has spread throughout Canada and the U.S.A. It evens threatens the Bristlecone Pine of California, some of which have thrived for over 3,000 years. Much research is going into developing disease resistant white pine with some limited success but not without its own controversy.

The fascinating story of the Eastern White Pine is woven throughout the history of North America and demonstrates the massive impact our actions can have on our environment.