Oak wilt

Oak Wilt is a fungal disease that affects oak trees, particularly red oaks (e.g., black oak, pin oak, red oak) and, to a lesser extent, white oaks (e.g., bur oak, white oak). Oak Wilt comes from the fungus Ceratocystis fagacearum. Oak wilt is a severe disease that can cause rapid tree decline and death.

Oak wilt spreads primarily through root grafts, which are connections between the roots of neighboring oak trees. The fungus transmits by insect vectors, such as sap beetles, which can carry fungal spores from infected trees to healthy trees. Additionally, oak wilt can spread through wounds on oak trees, such as pruning cuts or injuries.

Symptoms of oak wilt can vary depending on the oak species but typically include wilting and discoloration of leaves, starting from the top of the tree and progressing downward. Infected trees may also exhibit leaf drop, defoliation, and dieback of branches. The disease can move quickly, with infected trees dying within a few weeks to several months.

Managing oak wilt involves implementing preventive measures, such as avoiding pruning or injuring oak trees during the active growing season when the fungus is most likely to spread. If oak wilt is detected, affected trees may need to be removed and destroyed to prevent the further spread of the disease. Fungicide treatments can sometimes be used to protect healthy trees from infection. It's essential to consult with a certified arborist or other tree care professional for accurate diagnosis and appropriate management strategies if you suspect that your trees are affected by oak wilt.

Ganoderma

Ganoderma is a type of fungus that can cause root rot in Oak trees. Trees affected by the fungus rot may exhibit yellowing, wilting, or undersized leaves and dead branches. Tree vigor may decline as the decay of the sapwood advances. The first visible sign of infection is often the formation of fruiting bodies (single or in clusters) on the lower trunk and exposed root areas. The fruiting bodies are conks: shelf-like in appearance, and up to 14 inches wide. The upper surface of varnished fungus rot is typically red-brown with a white edge, shiny, and lacquered appearance. Conks of the unvarnished fungus rot are brown with a white edge weathering to grey. Both have a white, porous surface (when fresh) on the underside. This disease can kill young trees as well as older, larger ones. Unfortunately, it is too late to reverse the infection when the conks are present. The decay rate can lead to death in as little as 3 to 5 years from disease and appears to be determined by tree vigor, which is often influenced by environmental stresses.

Armillaria

Armillaria is a genus of fungi that includes the A. mellea species known as honey fungi that live on trees and woody shrubs. It causes Armillaria root rot in many plant species and produces mushrooms around the base of trees it has infected. Armillaria root rot causes poor growth, yellow to brown foliage, and eventual death of the tree. Trees infected with Armillaria root rot have decayed roots and lower trunks. These trees often break or fall over in storms.

The symptoms of Armillaria are similar to those of other root disorders; reduction in height growth, sparse foliage, and leaves that remain on plants are stunted and yellow. An abnormal flow of sap may be visible on the root collar. When soil is removed from the base of the trunk, black, root-like strands are visible and attached to more extensive roots. White to dark, fan-shaped mats of fungal strands develop between the bark and wood in infected root and trunk tissues. The most positive sign of infection is the production of clusters of honey-colored mushrooms at the base of the tree near the soil line. The mushrooms may have stalks 4 to 6 inches high with caps 1 inch tall and 2 to 4 inches wide.

Hypoxylon canker

Hypoxylon canker is a fungus that causes cankers and the death of oak and other hardwood trees. The disease is common in Kansas and all across the southern United States. Relatively healthy trees are not invaded by the fungus, but the hypoxylon fungus will readily infect the sapwood of a tree that has been damaged, stressed, or weakened. Natural and man-caused factors that can weaken a tree include defoliation by insects or leaf fungi, saturated soil, fill dirt, soil compaction, excavation in the root zone of the tree, removal of topsoil under the tree, disease, herbicide injury, drought, heat, nutrient deficiencies, competition or overcrowding, and other factors. Hypoxylon canker activity usually increases when prolonged drought occurs. When drought stresses trees, the fungus is able to take advantage of these weakened trees. The hypoxylon fungus is considered a weak pathogen because it is not aggressive enough to invade healthy trees. In addition to the hypoxylon fungus, weakened and stressed trees may become susceptible to other insect and disease pests.

Integrated Pest Management Strategies for these common pests

1. Remove and destroy infected material. Remove as much of the stump as possible. Sterilize tools with 1–part bleach solution with 9–parts water after use.

2. Provide adequate moisture in well-drained soil to maintain vigor and resistance to infection. Plants suffering from drought are incredibly susceptible to infection. Fertilize trees appropriately in late winter or early spring.

3. No adequate chemical controls are known. Plants reported by Auburn University to be resistant to Armillaria root rot include ginkgo, tulip tree, ash, bald cypress, cherry, Chinese elm, Chinese pistache, crabapple, cryptomeria, dawn redwood, eucalyptus, hackberry, holly, incense cedar, Leyland cypress, maidenhair tree, maple, privet, smoke tree, sweetgum, tree-of heaven, white fir, and wisteria. These should be considered for the replacement of diseased trees. New soil should be used to amend the planting site. All diseased material and associated roots, as much as possible, should be excavated before replanting.

A few other pests to watch out for:

Oak Gall, Tabukia, foliage fungus

If you are concerned with your oak trees, please call our certified arborist for an evaluation.

Common Oak pest in the Kansas city region