Transcript Texas Oak Wilt Information

Texas Oak Wilt Information
Adapted in part from the Forest Service,
Southern Research Station publication How to
Identify and Manage Oak Wilt in Texas
What is Oak Wilt?
• It is one of the most destructive tree
diseases in the United States;
• Oak wilt is an infectious disease caused
by the fungus Ceratocystis fagacearum;
• It invades and disables the waterconducting system in susceptible trees;
Oak susceptibility:
• Members of the red oak group are susceptible:
–Live oak,
–Shumard red oak,
–Southern red oak,
–Spanish oak,
–blackjack oak,
–pin oak and water oak
• Members of the white oak group including Bur
oaks, white oaks and post oaks, rarely
become infected because of their high level of
resistance. When infected, they seldom die.
COLLIN
COUNTY
Oak Wilt Occurrences in Texas
Counties as of January, 2003
Identifying Oak Wilt
• Foliar symptoms
• Patterns of tree
mortality
• Presence of fungal mats
* Laboratory isolation of
the fungus is
recommended to
confirm the diagnosis
Gillespie County ExtensionTexas Hill Country
Foliar Symptoms
• Chlorotic veins
become necrotic;
• Interveinal
chlorosis;
• Margin or tip burn
• Rapid defoliation;
• Dead leaves with
brown veins often
found under tree;
Patterns of Tree Mortality
• Most live oaks
defoliate and die over
a 1-6 month period, a
few escape infection;
• Red oaks seldom
survive oak wilt and
often die within 3-4
weeks following initial
appearance of
symptoms.
Fungal Mats are spore producing
structures
•
•
•
•
Often found in the spring on trees
showing advanced symptoms of
oak wilt the previous summer;
Found in inconspicuous narrow
cracks in the bark of dying red
oaks leading to hollow areas
between the bark and wood;
Odor similar to fermenting fruit;
Expose for inspection by
chopping away the loose bark.
Insect spread of the Oak Wilt Fungus
Nitidulid beetle
Oak wilt is spread by two
methods, root transmission
and by sap-feeding
(Nitidulid) beetles.
Root Transmission
The fungus spreads
from tree to tree through
connected roots, either
by root grafts or through
a common root system.
Treatments for Oak Wilt Infected trees
1. TRENCHING:
Stopping the
spread through
the roots:
Measures can be
taken to break
root connections
between live
oaks or dense
groups of red
oaks to reduce or
stop root
transmission of
the oak wilt
fungus.
Sever roots by trenching at least 4 feet deep with
trenching machines, rock saws or ripper bars
Untreated trees immediately
outside the treated area should
be closely monitored for several
years.
Treatments for Oak Wilt Infected trees:
2. FUNGICIDE TREATMENT: Treatment success depends
on the health condition of the candidate tree, application
rate, and injection technique. Injection should be done
only by trained applicators.
Oak Wilt Prevention
• Immediately paint all wounds on oaks to prevent
contact with contaminated beetles.
• Avoid wounding of oaks between the period of
Feb. 1 - June 1.
• Do not transport or buy unseasoned firewood.
• Promptly remove and either burn or bury all red
oaks that are dying or have been recently killed
by oak wilt.
• To protect from other diseases sterilize/sanitize
all pruning equipment between trees.
Pruning Oak Trees
• Always paint pruning cuts as soon as the
cuts are made. All cuts greater than 1/2
inch should be painted.
• When possible prune trees between
December 1 and February 1, or between
July 1 and October 1. The heat of
summer and the cold of winter are when
the beetle populations are the lowest and
fungal mats are least likely to form.
Firewood
• Cuts from trees that form oak wilt mats can
spread the fungus. If the source is questionable,
cover with clear plastic and anchor it into the soil
to prevent insect spread.
• Smoke from burning diseased logs does not
represent a problem. Heat from the fire kills all
spores or beetles that might be present.
• For trees that die in the spring or early summer,
firewood can be safely cut by the fall.
Where to send samples to be diagnosed
for Oak Wilt:
Texas Plant Disease Diagnostic
Laboratory, Room 101, L. F. Peterson
Bldg. Texas A&M University,College
Station, TX. 77843-2132
Telephone No. (409) 845-8032
• To aid in the diagnosis the following
information is helpful:
• When did the problem develop?
• How many trees are involved?
• Does the problem appear to be spreading?
• Has anything been done over the root
system of the tree? As a rule of thumb, the
root extend beyond the trunk 2.5 to 3X the
distance between the trunk and the tree's
drip line.
• If trees are dying, how fast is the mortality?
Contact your County Oak Wilt
Specialist, County Extension
Horticulturist, Texas Forestry
Representative or Extension Plant
Pathologist for more information on
Oak Wilt.
Texasoakwilt.org
Texas Counties with Master
Gardener/Master Naturalist Oak Wilt
Specialists
Oak Wilt Specialists
Counties with Oak Wilt
HAVE A PLANT QUESTION?
Call our Horticulture help line at
(972) 548-4232
Collin County
Master Gardeners Association
www.ccmgatx.org
email: [email protected]