BLACK STAIN ROOT DISEASE

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BLACK STAIN ROOT DISEASE Reading Chapter 12
(text) Hansen, E. M., D. J. Goheen, P. F.
Hessburg, J. J. Witcosky, and T. D. Schowalter.
1988. Biology and management of black-stain root
disease in Douglas-fir. P 63-80. In T. C.
Harrington and F. W. Cobb, Jr. (eds.)
Leptographium root diseases on conifers. American
Phytopath Soc. Press, St. Paul, MN
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Distribution of black-stain root disease -
Tainter and Baker 1996
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Black Stain Root Disease Factoids 1. Caused by
Ophiostoma wageneri - Ascomycete
fungus Imperfect form - Leptographium wageneri
(formerly Verticladiella wageneri). 2. A
vascular root disease 3. Native disease - Occurs
only in western U.S. and southwest Canada 4.
Not a serious disease in commercial forests, but
has potential to be important. Seems to be made
worst by forest management (road construction and
thinning). Increased greatly in past 30 years 5.
Hosts - pines - Jeffrey, knobcone, ponderosa,
pinyon, singleleaf pinyon, eastern white, western
white, sugar, and lodgepole and
Douglas-fir Problems - Douglas-fir in OR and
WA Ponderosa and Jeffrey pines - N. CA,
singleleaf pinyon - southern CA
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6 Involves 3 strains - pinyon pine, other pines,
Douglas-fir. 7. Spreads by mycelia through root
to contact, by insects (root weevils and beetles)
and can grow short distances in soil. 8. Fungus
infects seedlings and older trees. 9. When
fungus invades tree it passes through the phloem
and cambium, but otherwise it is confined to
xylem and mature tracheids.
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Effects Black stain root disease is a vascular
wilt disease that does not actually cause a decay
of root or stem tissue. It kills trees by
blocking their water conducting vessels. Tyloses
form in cells. It can cause substantial
mortality. Disease centers appear as small
(usually less than 0.04 ha or 0.1-ac) groups of
dead and symptomatic trees. Much larger centers
occur sometimes, especially in ponderosa pine
stands. Dead trees, unless also affected by other
root disease organisms, usually remain standing.
Trees with black stain root disease are
frequently predisposed to bark beetle
infestation.
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Ecological Role O. wageneri creates stand
openings, enhances diversity, provides wildlife
habitat, and alters forest structure,
composition, and succession. The impact of Black
stain root disease should be considered from the
perspective of how it will influence the ability
to attain the desired stocking necessary for
meeting management objectives. As with other root
diseases, high levels of inoculum in relatively
pure stands of susceptible species may preclude
achieving adequate stocking in the future.
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Life History Once introduced into a tree, the
fungus can move to new hosts across root contacts
or by growing up to 15 cm (6 in) through the
soil. Centers may expand radially at a rate of
nearly 1 2/3 m (5 ft) per year. Long distance
spread involves root-feeding bark beetles
(Hylastes nigrinus) and weevils (Steremnius
carinatus and Pissodes fasciatus). Fruiting
bodies of the pathogen form in the galleries of
the insects, and the sticky spores that are
produced adhere to emerging insects and are
dispersed by them. The spore-carrying bark
beetles and weevils feed and breed in roots of
low-vigor trees so occurrence of new black stain
root disease centers in disturbed areas probably
results from vector preference for stressed or
injured trees. The fungus is relatively
nonpersistent and cannot be isolated from
previously infected wood much more than a year
after the tree dies.
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Identification Trees with black stain root
disease usually exhibit sparse, chlorotic crowns
and reduced growth. Some trees also show
distressed cone crops and basal resinosus.
Occurrence of dark brown to purple-black stain in
the sapwood of infected roots and lower stems is
diagnostic.
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Symptoms in Douglas-fir, CA
Symptoms in ponderosa pine, CA
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Symptoms in singleaf pinyon, CA
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Douglas-fir stain
Douglas-fir stain
Transverse section in pine, CA
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Black stain root disease in lodgepole pine
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Black stain in roots
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Ophiostoma hyphae Fungus moves from cell to cell
via bordered pits. Cant penetrate through cell
walls.
View of hyphae in Douglas-fir tracheids (Hansen
et al.1988)
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Black stain in young Douglas-fir stands
in Oregon and Washington
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Young Douglas-fir showing crown symptoms
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Habitats where it develops Black stain root
disease usually is found in areas where there has
been significant site disturbance or substantial
amounts of tree injury, especially in
precommercially thinned stands, along roads and
skid trails, on sites with drought-stressed,
waterlogged, or compacted soils, or where rotary
blade brush cutters have been used to clear
roadsides.
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Vectors - root weevils and bark beetles
Steremnius caritinus (root weevil)
Hylastes nigrinus (Bark beetle)
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Steremnius and Hylastes trapped in precommercially
thinned and unthinned plots in 1983
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Management Minimizing disturbance is an
important component of a black stain root disease
management strategy. This would include avoiding
soil compaction and disturbance of the soil
profile. Sites with soils particularly prone to
compaction by heavy equipment should not be
tractor logged. Where timber harvest occurs,
high-lead and skyline yarding would be preferred
over tractor logging. If tractor logging is the
only option, skid trails should be designated,
the area covered by skid roads should be
minimized, tree falling should be done to the
yarding lead, and yarding should be restricted to
the dry season when the risk of serious
compaction is reduced. New road construction
through high risk areas should be avoided. If
construction occurs or old-roads must be
re-opened, injured trees or those covered by
side-cast fill should be removed. Efforts should
be made to avoid injuring trees to be retained on
site. This should preclude the use of
rotary-blade brush cutters on roads adjacent to
high risk areas.
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In high risk areas, particularly those stands
within 1.6 km (one mile) radius of known black
stain root disease centers, juvenile spacing
should be scheduled between late June and early
September if possible. This coincides with the
period after the vectors of black stain have
emerged and established themselves for breeding
in other dead, dying, or down trees and helps to
limit vector population build-up. Efforts should
be made to plan for a diverse mix of species in
areas where black stain is a known management
concern. In areas where black stain is already
causing mortality, resistant or immune species
should be favored when possible. This is
particularly important in active infection
centers and the buffer zones immediately adjacent
to them. Where resistant species are lacking and
harvest activities are necessary, active
infection centers and their buffer zones should
be avoided