Heterobasidion Root Disease

Heterobasidion Root
Disease
Managing to Prevent Pathogen
Introduction
Jennifer Juzwik
NRS, U.S. Forest Service

Root Diseases: The Hidden Enemy
Armillaria root disease
(Armillaria ostoyae)
Tomentosus root disease
(Onnia tomentosa)
Brown root and butt rot
(Phaeolus schweinitzii)
Ganoderma root and butt rot
(Ganoderma applanatum)
Heterobasidion
root disease
(Heterobasidion
irregulare)

Heterobasidion root disease is one of the most
economically important diseases of conifers in the north
temperate zone.

Some Heterobasidion root disease basics
• HRD is endemic on susceptible hosts in North
America, Europe, and Asia,
• Conifers are the major hosts,
• HRD causes growth loss and mortality in
Pinus species,
• HRD is especially important where intensive
thinning and monoculture are practiced,
• HRD is very difficult to impossible to eradicate
from a stand once the pathogen is
established.

HRD has become a major concern in Wisconsin
since the disease was first detected in 1993.
First Detection
Current Situation
1993 – Adams Co.
1994 – Iowa Co.
23 counties with HRD
Confirmed in > 50 stands

Why has HRD become such a problem in Wisconsin in less
than 20 years
Due to failure to detect or recognize the disease before 1993
Was HRD possibly mis-diagnosed as red pocket mortality
at times
Has thinning in pine plantations without preventive
treatment led to spread and intensification of HRD

What is the situation in Minnesota
A fruiting body (conk) has
been collected from
Itasca State Park, but
HRD has not been
detected in the state
Potential exists for natural
spread of pathogen spores
from western Wisconsin to
pine stands on MN-WI
border.

Disease biology and pathogen
spread

Heterobasidion annosum is a fungus with a species
complex.
Ha is comprised of intersterile biological species defined
as intersterility groups (ISGs).
--- Includes at least two distinct North American and three
distinct Eurasian ISGs.
Nomenclature of Heterobasidion annosum species complex
Prior to 2010
• Heterobasidion annosum
– P ISG Pinus species
– S ISG Abies and Tsuga
2010 to present
• Heterobasidion irregulare
– eastern North America
• H. occidentale – western
North America

The pathogen primarily spreads by aerially
dispersed spores and by root contact between
adjacent trees.
Aerially borne
basidiospores
Stump
infection
Direct root
infection
Root contact
spread

Seasonal variation in spore dispersal has been
documented for plantations in central Wisconsin.
Spore-trapping
Sept 2009 – Dec 2011
• Asexual stage of fungus grew
on plates exposed every month
of the year.
• Fungus colonies most
abundant during late summer,
fall and early winter.
• Only a few colonies developed
on plates exposed during
January and February, but
colonies did develop from plates
exposed just below freezing.

Once established in a stand, H. irregulare spreads
outwardly from infected stump to form disease
centers (“circles of death”).
Source: G. Stanosz, U. Wisc. - Madison

Susceptible coniferous hosts and other species that
support fruiting body production
• HRD common in red pine
and white pine
plantations in Wisconsin
and jack pine plantations
in Quebec.
• The fungus also occurs
on Picea glauca, Abies
balsamea, and other
conifers in Wisconsin.
• Fruiting bodies found on
hardwoods, shrubs &
decaying wood.

Diagnosis of HRD requires some “detective” work.
Site and tree symptoms
• Thinning crown with
fading foliage
• Circular pattern or
within row occurrence
of symptomatic or dead
trees
Signs – fungus fruiting body
On decayed stump
At base of live tree
Sampling and lab diagnosis
• Excavate 2 main
roots on opposite sides
of suspect tree
• Remove a 6 to 10
inch segment of the root
• Submit to diagnostic
laboratory
In forest floor litter
“popcorn” like fruiting bodies

Approaches to disease management

Avoidance:
Hazard rating systems are used in southeastern USA to guide
foresters in rating planting sites for risk of HRD.
Site factors and stand history
conducive to root rot
• Sand, loamy sand, and
sandy loam soils at least 12
inches deep
o Good internal drainage
o Low seasonal water
table
• Old agricultural lands
HRD risk map for Georgia

Prevention:
Treatment of stumps with borate product during thinning
operations or clear felling is a key control tool.
Granular
product
applied by
sprinkling on
stump surface
Water soluble
powder
applied by
spraying on
stump surface

Application of liquid borate
Dye added

Application of products
Timing
• During what season or
what months should
fresh stumps be
treated
Treatment during winter
temperatures (20 to 32 F)
requires addition of
propylene glycol to liquid
borate
• How soon after felling
should stump be
treated

Eradication:
Stump extraction has been tried in at least one northern
location.

Guidelines for HRD management in northern states
• WI DNR: Managing
HRD
– When scattered
throughout stand
– When rare in stand
– When not in the stand
See:www.dnr.state.wi.us/topic/
ForestHealth/Annosum
RootRot.html
NOTE:
• A Revised Managers
Handbook for Red Pine in
the North Central Region
(2006)
o OUTDATED info on
Annosum root disease
National Forest Lands
Approach (MI, MN, WI)
• Consider proximity of
stand to known HRD
stand
• Consider management
situation
• Advised mitigation
strategy – based on
response to above
Contact: Linda Haugen, NA S&PF, St. Paul
lhaugen@fs.fed.us

What can you be doing about HRD now
• Train marking, stand
exam and inventory
crews to recognize HRD
and H. irregulare conks
• Actively look for the
disease
– Conduct surveys
– Examine trees in suspect
mortality centers
– Be aware of where nearest
HRD is located from pine
stands
• Submit samples from
“suspect” sites or report
to a forest health
specialist
Source: FHP staff, NA S&PF, U.S. Forest Service
Photo source: en.wikipedia.org

Acknowledgements
Kyoko Scanlon
Forest Pathologist
Wisconsin DNR
Dr. Glen Stanosz
Forest Pathologist Prof.
Univ. of Wisc. - Madison
Linda Haugen
Plant Pathologist
NA S&PF, USFS

Questions and Discussion