Oak Wilt
Range
Oak wilt is the most serious disease of oaks.
Damage in central and eastern U.S.
Recently spread to Texas where it has caused extensive damage on live oak.
Assumed to be native, since it is only found in the U.S., but there is no explanation for its recent spread.
Hosts - Oaks (
Quercus
spp.)
Red/black oaks (Erythrobalanus) - highly susceptible
White oaks (Leucobalanus) - much
more
resistant, but not immune.
Known host species (all are oaks): black, blackjack, bur, chestnut, Durland, Lacey, southern live, West Texas live, overcup, pin, northern pin, post, northern red, southern red, Texas red, scarlet, shingle, turkey, water, white
Additional species are susceptible
by inoculation:
apple, chestnut, chinkapin oak, and tan oak
Ceratocystis fagacearum
- the causal agent
Two spore forms
Chalara
anamorph (asexual state)
Ceratocystis fagacearum
-
teleomorph (sexual state)
Both forms are produced on mycelial mats beneath the bark of recently-killed trees
Pressure pads expand and bark cracks.
Fungus emits a fruity odor which attracts insects.
Vectors
In the North picnic beetles in the family Nitidulidae are the primary vector.
Glischrochilus sangunolentus
Other vectors include bark beetles in the Scolytidae
Pseudopityphthorus minutissimus
Pseudopityphthorus pruinosus
Disease Cycle
Symptoms
develop in spring and early summer.
Vessels become
discolored.
Red oaks are more susceptible than white oaks.
Control
Avoidance - restrict logging and pruning to avoid wounding trees in the spring and summer when the risk of infection is higher.
Discourage mat formation
Deeply girdle sapwood (reliable?)
Cut just killed trees (reliable?)
Cut and
remove
just killed trees before mats form.
Cut grafts:
Vibratory plow
Ditching machine
An example.
Where do you put your trenches?
Chemical control
Inject fungicides which have been tested and labelled. This is time consuming because you must inject individual trees, and is only a preventative measure.
Debark and/or fumigate logs before transport to areas where the disease is absent.
back to vascular wilts
