Cottonwood trees across Bismarck are showing early leaf drop, a sign of fungal infection spreading through the city’s beloved shade trees.

Residents walking through Bismarck neighborhoods this fall may have noticed something unusual: cottonwood trees turning yellow and shedding leaves weeks ahead of schedule. According to local forestry officials, several species of fungi have taken hold, fueled by wet spring conditions followed by warm summer weather.

Cottonwoods are a cornerstone of Bismarck’s tree canopy, lining riverfronts, parks, and residential streets. Their sudden decline is raising concern about long-term impacts on shade, soil stability, and local ecosystems. Early defoliation also stresses the trees, making them more vulnerable to pests and future disease cycles.

For background on fungal diseases in regional trees, the NDSU Extension Plant Pathology resources provide guidance on symptoms and management options.

The City of Bismarck Forestry Division has begun field inspections, advising homeowners to rake up and dispose of infected leaves to slow the spread. City crews are also prioritizing monitoring cottonwood clusters near schools, parks, and public walkways.

Homeowners are being urged to keep trees watered through the fall and to avoid unnecessary pruning, which could open fresh entry points for disease.