What is considered the most damaging hardwood disease?

Heart rot is recognized as the most damaging hardwood disease primarily due to its significant impact on the structural integrity of trees, particularly in hardwood species. This disease primarily affects the inner wood of a tree, leading to the decay of the heartwood, which is crucial for the tree's stability and strength. As heart rot progresses, it compromises the tree's ability to withstand environmental stresses such as wind and snow, making it more susceptible to breakage and failure.

The damage caused by heart rot is particularly concerning in commercial timber species, as it can greatly reduce the economic value of the wood. Additionally, infected trees can often appear healthy externally, which complicates detection, leading to situations where decayed trees may be left standing until the damage becomes severe. This can pose risks not only to the trees themselves but also to surrounding forest ecosystems and human safety.

In contrast, while other conditions like leaf spot, sudden oak death, and canker can also negatively affect trees, they generally do not lead to the same level of structural failure that heart rot does. Sudden oak death specifically targets oak species and can cause significant mortality but does not affect the overall integrity of other hardwoods in the same pervasive and longstanding way as heart rot.