Persistent Rain Can Cause Tree Root Rot, Early Leaf Drop

Jul 22, 2019

Prolonged periods of rain and over-saturation of tree roots can cause root rot, which can impact a tree’s ability to consume water and nutrients. 

Soil saturation also makes it difficult for roots to breathe. Tree Pittsburgh Director of Urban Forestry Matt Erb said a lack of oxygen can cause roots to die or become infected by bacterial or fungal pathogens and that cause root rot. Root rot is when roots decay, ultimately causing the death of a tree.

“If you have a tree that’s already stressed due to storm damage at the top of the tree or an insect or a disease problem, when that tree gets flooded that additional stress is compounded … That stressed tree is more likely to get root rot,” Erb said.

Erb said root rot could be a factor in landslides because the root no longer holds onto soil. 

“A lot of hillsides are forested, and there are large, mature trees there, and those trees are coming down with the soil,” he said.

Erb said landslides are generally caused by a combination of factors including soil erosion and saturation. 

He said fungal root rot is often seen in older trees in Pittsburgh such as large oaks and beeches.

Signs of root rot include small pale, pale yellow or brown leaves and a thinning of the canopy. Erb said homeowners should plant trees away from areas where water pools to prevent root rot.

Wet spring and summer causes early leaf drop

Anthracnose damages trees and can be spread through dead leaves.
Credit Davey Tree Company

In addition to root rot, rain can cause another problems for trees: early leaf drop.  Sycamore and ash tree leaves are dropping early this year in Pittsburgh due to a leaf disease, anthracnose, according to Rob Kruljac, assistant district manager of North Pittsburgh Davey Tree Service.

Anthracnose is a foliar disease that also infects dogwood, maple and oak trees. It thrives when cool, wet spring weather persists.

Kruljac said the disease spreads from infected, dead leaves on the ground.

“It’s the perfect environment for the anthracnose to multiply and the spores to come out,” he said.

This fungal disease typically causes an aesthetic issue because the leaves fall off of the tree, Krulijac said, but they will grow back after the winter season.

According to Davey Tree Service, each tree will show the following symptoms if infected by the fungal disease:

· Ash trees: brown blotches appear on the leaf’s tips, veins and margins

· Maple trees: brown veins and irregular browning of margins that extends inward

· Oak Trees: creates large, dead areas between leaf veins

· Sycamores: leaf veins and adjacent tissue slowly turn tan and then brown

He said to prevent the disease, tree owners can do a spray treatment in early spring, and people can also clean up the diseased leaves that have fallen off of the tree.