How did Dutch elm disease affect temperate forests?

Dutch elm disease is a devastating fungal infection that has significantly altered temperate forest ecosystems in Europe and North America by decimating populations of elm trees.12

The disease is caused by three species of ascomycete fungi in the genus Ophiostoma, which are primarily spread by bark beetles. When these beetles feed on healthy trees, they introduce fungal spores into the xylem, where the fungus reproduces rapidly and obstructs the tree's water-conducting vessels. This leads to wilting, branch death, and often the total collapse of the tree. Beyond beetle transmission, the fungus can also spread between adjacent trees through natural root grafts.1

The impact on temperate forests has been profound, particularly for the American elm, which is highly susceptible to the disease. While various control measures—such as the removal of infected wood and the use of insecticides or fungicides—have been employed to protect individual trees, the disease remains a persistent threat that has drastically reduced the presence of elms in both wild and cultivated landscapes.12