Infected Campus Trees

by Robert Mumby

The RVM campus is blessed with many trees that provide us with beauty, shade, erosion control and store ground water. They also provide food and habitat for the many birds and other critters that live here.

Trees are subject to attack by animals, fungi and diseases. The recent years of drought and unusually hot weather have greatly stressed many of our trees and this weakens them. As a result, some are damaged or dying from infections from fungi and other pathogens. There are visible symptoms: extruded sap that tries to wash out the pathogens, cracked bark, strange bulges, to name the most obvious signs.  Broken limbs, holes, or cracked bark provide an opening for infection, just as a cut in our skin does.  Some trees may slowly die and we hardly notice, but large trees with weak roots could fall and damage property.

Drew Gilliland, RVM Director of Facilities Services, said “the RVM grounds department addresses infected trees on a case by case basis that evaluates several factors such as type of tree, location, weather patterns and mitigation strategy.  In some cases nothing will be done, and other cases appropriate levels of pesticides may be applied following our overall integrated pest management plan.  In many cases with unknown threats, an arborist is contracted or the OSU Extension Offices is contacted to consult on recommended mitigation issues.”

Drew also pointed out that extensive use of pesticides to save a single plant may have damaging effects on the larger environment, and that the age and expected lifetime of a tree are also factors considered in deciding on possible treatments.

Illustrations of some actual or potential infections are provided at the end of the article.

Western Gall Pine Rust forms rough globular galls on trunk or branches. Galls are proportionate in size to the branches bearing them. When the fungus is fruiting (aecia), galls are orange or yellow. Galls may kill small trees but increase in size for many years on larger trees. Trees may break easily at the gall.

Shaggy Bracket fungus  is classed as a white rot decay fungus and can cause white rot, and occasionally soft rot in trees that it lives off. It is an aggressive decaying agent which weakens timber, trunks and branches.

Pathogenic fungi, such as Western Gall Pine Rust or Shaggy Bracket will infect nearby trees by releasing spores, so treatment may be a desirable option.

Clumps of mistletoe do not damage trees unless there are many large clumps growing all over a tree. Mistletoe berries are an important food source for many birds, including Western Bluebirds, and the parasite provides shelter and a nesting place for birds and squirrels.

The main dangers of infections are that a large limb may be weakened and fall causing injury or damage or that the tree’s roots will be destroyed, leaving the tree subject to falling, especially during strong winds.

Bulge in Oregon Oak tree may indicate an infection.

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Flattened Thornbush Lichen on Oregon Oak.  Effect on tree unknown at this time.

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This Oregon Oak tree has a hole that may have been caused by a woodpecker for a nest or been used by a Tree Swallow. Note loose bark below hole. These are openings that will facilitate fungi or invertebrate infestations.

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Shaggy Bracket, a fungus, may eventually kill this Oregon Oak tree. This visible portion will produce spores that may infect other trees.

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This small pine tree next to the golf course is heavily infected with Western Pine Rust; other trees near the cottages are also infected.