Trees are important to the environmental health of cities through their capacity to improve air quality, provide cooling via shade and transpiration, and foster natural beauty.

Common_lime_during_an_autumn_sunset,_Christchurch,_New_Zealand

Source: Michal Klajban

Common lime during an autumn sunset, Christchurch, New Zealand

New research in Plant-Environment Interactions reveals how the widespread plant pathogen Phytophthora affects urban trees, specifically Common Lime trees.

READ MORE: Chloroplast manipulation: A new strategy in pathogen warfare uncovered

READ MORE: Study analyzes potato-pathogen ‘arms race’ after Irish famine

Using numerous tree sensors, investigators found that infected trees exhibited reduced water use and stem growth compared with healthy trees, but some still managed to maintain growth and cooling benefits.

Tree trade-offs

The findings highlight the complexity that tree managers and policy makers must consider when attempting to control disease spread while maintaining the benefits of trees in cities. There are potential trade-offs to consider when weighing tree removal to limit disease spread against the benefits provided by well-functioning diseased trees, particularly large-stature, mature trees that have the greatest capacity to enrich urban areas.

“The impact of Phytophthora disease on the studied street trees was variable, even under extreme heat events that occurred in the UK in 2022, highlighting possible tensions between tree disease management and ecosystem service provision,” said corresponding author Eleanor Absalom, PhD, of the University of Sheffield, in the UK. “Given the growing threats of disease outbreaks and climate change, a better understanding of the impact of Phytophthora on urban trees is critical to maintain resilient urban forests.”