By Scout Nelson
American elm trees are among the most recognized and valued trees in North Dakota. They grow quickly, adapt well to different environments, and provide excellent shade with their beautiful vase-shaped canopy. However, Dutch elm disease continues to threaten these trees and remains one of the biggest challenges for communities trying to preserve their urban forests.
Joe Zeleznik, Forester, NDSU Extension, explained that Dutch elm disease is a complicated problem because it involves both fungal pathogens and bark beetles that spread the disease from one tree to another. He emphasizes that successful management depends on early detection, prompt action, and strong community support to protect healthy elm populations.
Dutch elm disease is caused by fungi that enter a tree through bark beetles or through connected root systems between nearby elm trees. Once inside, the fungi block the tree's water-conducting tissues. As a result, branches begin to wilt, leaves curl and turn yellow, and the upper canopy gradually dies. Trees infected through root connections may show sudden wilting across the entire crown.
Treating infected trees is often difficult. Removing infected branches quickly is challenging, and fungicide treatments applied after infection are usually less effective than preventive treatments applied before disease develops.
The most successful management practice is sanitation. This involves identifying infected trees and removing them within two to four weeks. Quick removal eliminates breeding sites for bark beetles and reduces the spread of the disease to nearby healthy trees.
Communities that actively follow sanitation programs lose only about one to two percent of their American elm trees each year. Without these efforts, annual losses may increase to ten to twenty percent, eventually eliminating nearly all elm trees within a decade or two.
Some cities use tree ordinances to require the removal of infected trees, while others depend on voluntary cooperation from property owners. Preventive fungicide treatments can also protect valuable trees, although these treatments require additional investment.
Photo Credit: pexels-mayukh-karmakar
Categories: North Dakota, General