Oak Wilt

Fungal disease effecting oak trees and their timber logging, fungus attacks xylem, causing trees to plug xylem vessels to block the disease.

Latin Name

Ceratocystis fagacearum

Trees Affected

Oak (all), red oak is more susceptible than white oak; American, European & Chinese chestnuts, and some apple species

Threat to Trees

Moderate

Onset

Red oak mortality may occur as early as 1 or 2 months after disease manifests, most trees die within 1 year. White oaks decline more slowly, killing some branches each year. White oaks may fight the disease and recover (though they often harbor pathogens from the disease), or eventually die after succumbing to the disease.

Transmission/Vector

Fungus is spread by sap and bark-feeding beetles, especially when attracted to the scent of fungal mats. Root grafting can also infect adjacent trees.

Signs & Symptoms

Beginning in early spring, leaves turn a dull green, or bronze, appearing water-logged. Wilting occurs, followed by a change to yellow or brown. Damage occurs from tips towards the midrib and base of the leaf. Some curling may occur around the midrib. A distinct line between green and wilting areas is very distinguished. Heavy defoliation occurs, of leaves of varying colors and stages of wilt, including green leaves. Symptoms appear very similar to drought conditions.

Red oak: Fungal mats are common on the trunk under the bark, sometimes leading to cracking and odors.

White oak: no fungal mats

Description

In a survey of eight Wisconsin counties, 11 percent of annual growth was offset by oak wilt mortality. However, states like West Virginia with 70% forest coverage made up of predominantly oak trees, wilt loss is less than one tree per square mile on average per year. 50% of diseased trees contail beetles and 25% produce fungal mats.

Domestic Origins

Wisconsin, 1944

Geographic Location

Found across 21 states, most notable damage occurring in the Midwest

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