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Best Management Practices
There are currently no known cures or preventatives for SOD. Research is
underway studying the efficacy of various fungicides, but results are
unavailable at this time. There are preliminary reports of success with
fungicide applications on young tanoaks and coast live oaks. Until specific
information on the SOD pathogen is available, the best management practices
described herein are based largely on the known pathology of other
Phytophthora species. It should be noted that not all trees in an infested
stand become infected, however, genetic-based resistance has not been confirmed.
The SOD pathogen produces reproductive structures that in other Phytophthora
are spread by soil, water, and infected host material, especially under mild,
moist conditions. Patterns of SOD spread suggest aerial dispersion as well.
Phytophthora ramorum has been found in rainwater collected below infected
coast live oak stems, and from soil around these trees. The pathogen may be able
to survive in a resting stage for substantial intervals of time, and is viable
for a period of time on dead wood (12). Practices that reduce the spread of the SOD
pathogen within SOD-infested areas, and between SOD-infested areas and
uncontaminated sites, are the primary methods of control at this time. If soil
is confirmed as a viable SOD vector, the greatest threat of spread will occur
when the soil is damp or wet, and readily adheres to feet, shoes, tires, and
construction and tree removal equipment (13).
SOD-Infested Areas
- Do not transport any confirmed host species out of areas of known SOD
infestation. Avoid the movement of any potentially infected material within
or out of the zone of infestation.
- Do not transport plant parts (acorns, leaves, firewood, etc) of any
confirmed host species out of areas of known SOD infestation. Avoid the
movement of any potentially infected material within or out of the zone of
infestation.
- Do not transport any wood products such as mulch, bark, or firewood
taken from confirmed host species out of areas of known SOD infestation.
Leave felled trees on site if possible. Chip and scatter branches on site.
Do not leave wood near roads where it may be removed from the zone of
infestation and used as firewood. Keep wood piles as far away from
susceptible hosts as possible. Cover wood with plastic to prevent beetle
emergence and weaken Phytophthora (See Details Below). Clean all
chain saws, handsaws, axes, mauls, wedges, splitters, and other equipment
with a cleaning agent as described in Section VI, Sampling.
- Do not transport soil, duff, organic matter, or other substrate out of
areas of known SOD infestation.
- Avoid driving or parking vehicles in SOD-infested areas where they may
become contaminated with soil or mud.
- After visiting a known SOD-infested area, clean the soil from your
shoes, sporting equipment, vehicle tires, construction equipment, and pets
just before leaving the site.
- Avoid SOD-infested areas when possible, especially during mild, moist
conditions. When hiking in SOD-infested areas, avoid walking in damp or wet
soils if possible.
- In a landscape situation, replace SOD-infected trees and shrubs with
non-susceptible species.
- Promote the health of non-infected trees and shrubs. Prune dead, dying,
and hazardous branches. Minimize root damage. Water during drought periods,
but avoid over-watering. Mulch with up to 4 inches of clean, coarse bark-not
around trunk. Fertilize with nitrogen only when a soil deficiency has been
verified. Avoid mechanical injury to the trunk and branches. Inspect trees
and shrubs regularly over the growing season for signs of infection and
initiate corrective measures as soon as possible.
- In areas where the western oak bark beetle (Pseudopityophthorus
pubipennis), oak ambrosia beetle (Monarthrum scutellare), and
minor oak ambrosia beetle (Monarthrum detinger) are know to exist
and attack oaks, apply labeled insecticides to control these insects thereby
reducing the risk of secondary attack and spreading SOD. Trees infected with
the SOD pathogen should be cut into firewood, the branches chipped, the
stump ground or completely covered with clear plastic. Cover all wood with
clear, 6-mil plastic for 6 months to prevent beetle emergence. Secure the
edge of the plastic with rocks and soil to prevent insect escape (11).
- Inspect ornamental rhododendrons and other SOD hosts used for
landscaping for signs of cankers that spread from twig tips to the base of
the stem. If infection is suspected, contact your local county agricultural
commissioner, State or federal forest health specialist, or University or
Extension pathologist. Once infection is verified (which typically requires
professional inspection, sampling, and/or laboratory verification), the
plant(s) should be properly eradicated.
- When a dead tree presents an unacceptable hazard, fall the tree along
the contour to reduce soil erosion. Chip and scatter branches on-site. Stack
wood in a manner that promotes rapid drying. Tarp wood on-site and only
under warm, dry conditions.
- Avoid pruning under mild, wet conditions that favor the spread of the
SOD pathogen. Sanitize tools as previously described.
- Keep the trunks of oak trees and the stems and foliage of other SOD host
species as dry as possible (12).
Areas Not Infested With SOD (in reasonable proximity to SOD-infested sites)
- Promote the health of non-infected trees and shrubs. Prune dead, dying,
and hazardous branches. Minimize root damage. Water during drought periods,
but avoid over-watering. Mulch with up to 4 inches of clean, coarse bark
(not around trunk). Fertilize with nitrogen only when a soil deficiency has
been verified. Avoid mechanical injury to the trunk and branches. Inspect
trees and shrubs regularly over the growing season for signs of infection
and initiate corrective measures as soon as possible.
- In a landscape situation, plant trees and shrubs that are not
susceptible to SOD.
- Do not import any confirmed host species from areas of known SOD
infestation to non-infested sites. Avoid the importation of any potentially
infected material into non-infested sites.
- Do not import plant parts (acorns, leaves, firewood, etc.) of any
confirmed host species from areas of known SOD infestation into areas free
of SOD infestation. Avoid the importation of any potentially infected
material into non-infested sites.
- Do not import any wood products such as mulch, bark, or firewood taken
from confirmed host species from areas of known SOD infestation into
non-infested areas. Clean all chain saws, handsaws, axes, mauls, wedges,
splitters, and other equipment with a cleaning agent as described in Section
VI, Sampling.
- Do not import soil, duff, organic matter, or other substrate from areas
of known SOD infestation into non-infested sites.
- Do not plant acorns or other seeds collected from areas of known SOD
infestation into non-infested sites. Avoid using confirmed host species in
areas likely to support SOD.
- Inspect ornamental rhododendrons and other SOD hosts used for
landscaping for signs of cankers that spread from twig tips to the base of
the stem. If infection is suspected, contact your local county agricultural
commissioner, State or federal forest health specialist, or University or
Extension pathologist. Once infection is verified (which typically requires
professional inspection, sampling, and/or laboratory verification), the
plant(s) should be properly eradicated (12).
< Back to Sudden Oak Death
Last Modified:
11/20/2007
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