Forest Diseases and Disorders: Current Knowledge and Best Practice Control Methods Ian Hood

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Forest Diseases and Disorders Current Knowledge
and Best Practice Control MethodsIan Hood

• ARMILLARIA

Forest Biosecurity and Protection
Forest Biosecurity Research Council 1 March 2005
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Main Causal fungi
Armillaria novae-zelandiae Armillaria limonea

• Indigenous in native forests
• Persist in stumps and roots when such forests
  cleared
• Infect new pine crops planted on cleared sites
  by means of root contact and rhizomorphs

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• Produce mortality gaps and chronically
  infected green-crowned trees (cryptic
  infection)

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Points to cover
1. Present knowledge
2. Ballpark costs to industry - now and
anticipated
3. Guesses on potential new threats
4. What research is needed on the disease - gaps?
5. What research is needed on control/managemen
t?
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Percentage volume growth loss (mid-rotation)
1st rotation on indigenous forest site 25 (21
early mortality, 4 increment loss)
2nd rotation non-indigenous forest site 3
(nil early mortality, 3 increment loss)
National loss attributable to Armillaria 2000
37 million 2020 20 million
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Dispersal by spores?
Indirect
Occurs in pine plantations (and elsewhere) with
no past indigenous forest history
Only A. novae- zelandiae in second rotation
stands on non-indigenous forest sites
Occurs in high genet density populations
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Armillaria population densities
A. gallica BEYOND NZ

A. ostoyae

A. borealis lt1 - 8
colonies/ha A. luteobubalina
A. ostoyae Pinus resinosa, Michigan BEYOND
NZ A. hinnulea Eucalyptus, Tasmania
26-54 colonies/ha
NEW ZEALAND Native forest/pine
plantation A. novae-zelandiae
13-109
A.
limonea
0-56 Both 13-131 colonies/ha
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Looking for direct evidence
Treating pine stem segments and stumps with spores
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Direct evidence?
Treating pine stem segments and thinning stumps
with spores
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Direct evidence?
Treating pine stem segments and thinning stumps
with spores
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But how feasible?
Spore dilutions - how low a spore density?
Some initial results
Spores/cm2 Proportion segments with
Armillaria cut surface Capped Not
capped 10 million 4/4 2/4 1
million 4/4 4/4 100,000 4/4
4/4 10,000 4/4 3/4
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But how feasible?
Spore dilutions - how low a spore density?
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Feasibility
Armillaria spore populations in the air?
Stem segments as spore traps
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Feasibility
Armillaria spore populations in the air?
Volumetric suction spore trap/DNA recognition
Burkard SporeWatch tripod suction trap
DNA to understand other Armillaria species in
NZ - Tod Ramsfield
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Potential new threats??
Widely distributed throughout New Zealand -records
Widely distributed within stands - survey (74
sites in 21 forests)
1st rotation after indig. forest 38 2nd
rotation on former indig. forest 10 1st rotation
after scrub 5 2nd rotation after
scrub 20 1st or 2nd rotation
on pasture/herb 3-5
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Potential new threats??
Cryptic Armillaria in an unthinned 6-year, second
rotation stand on a non-indigenous forest site
Mortality 3 Chronic infection 23 Thinning
stumps colonised by Armillaria 44 - 58
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Potential new threats??
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Potential new threats??
Cryptic Armillaria in an unthinned 6-year, second
rotation stand on an ex-indigenous forest site
Mortality 4 Total infection 21
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Other potential new threats??
Widespread cryptic Armillaria
infection - means pine plantations vulnerable
to change
Examples, actual and speculative

• Dothistroma in ponderosa and corsican pine

• Poison thinning

• Effluent spraying

• Eucalyptus fastigata as previous crop

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Other potential new threats??

• Occasional unexplained high Armillaria mortality

• Douglas fir - used as a resistant species

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Other potential new threats??

• Biosecurity export risk? - Armillaria in stacked
  butt logs

• Planting at final stocking with no thinning

• Risk from introduced Phaeolus schweinitzii? -
  infection facilitated by Armillaria?

- Unexpected - Caused concern
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Knowledge Gaps
Disease development - how is Armillaria
spreading? - spore dispersal research underway
Management and control

• How identify risk areas for subsequent
  treatment?

• New cost/effective treatment options

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Identifying risk sites for treatment
Relating mortality to total infection
Armillaria incidence in a 6-year second rotation
stand on non-indigenous forest site (scale in
meters)
Chronic (shaded gt 25)
Mortality (shaded gt 3)
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Identifying risk sites for treatment
Relating mortality to total infection
Armillaria infection in a 6-year second rotation
stand on an ex-indigenous forest site (scale in
meters)
Chronic (shaded gt 25)
Mortality (shaded gt 3)
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Knowledge Gaps - Alternative Control methods
Current control option
Remove stumps before planting new crop
Second rotation stands - Mortality 10-22
? 0.2-5 Chronic infection 67-85 ? 10-31
But stumping not practiced - Extra cost -
Identification of risk areas
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Knowledge Gaps Alternative control options
Influence of site, environment and host factors
FRST (underway) Downstream
control?
Ecology of stands - host competition
Thinning to reduce and stumps as a pathogen food
base Armillaria incidence?
Ecology of stands - influence of
Selection of stock type host stock type
to reduce incidence?
Biodiversity of pine stumps Biocontrol
treatment to - competition between
populations deny Armillaria its stump of
stump fungi food source?
Variation in genetic resistance Deployment
of resistant stock?
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Knowledge Gaps - Current Research Status
Host competition and pathogen food base
Incidence of Armillaria at 12 years, 5 years
after thinning and pruning at 7 years
infection
Treatments 1. Control, unthinned (810 stems/ha)
- unpruned 2. Thinned to 250 stems/ha - pruned 3.
Thinned to 250 stems/ha - pruned no stumps 4.
Unthinned - pruned 5. Thinned to 500 stems/ha -
pruned
Ongoing further thinning and re-assessment to
see if trends continue
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Knowledge Gaps - Current Research Status
Nature of host stock type
Incidence and severity of Armillaria in different
stock types in genetically related seedlings and
cuttings at age 6.5 years (2 ha blocked trial,
row plots)
Stock type mortality total
infection Seedlings 5.9 a 25.7
a Stool-bed cuttings 3.3 ab 17.8
b Field cuttings 1.9 b 18.8 b
Resistance related to stock vigour
Ongoing subsequent re-assessment to see if
trends continue
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Knowledge Gaps - Current Research Status
Ecology of pine stumps - competition between
decay fungi
Early study decay fungi identified with ability
to compete with Armillaria in a wood substrate
Current - 34 different decay fungi cultured
from pine stumps - 10 from more than one stump
or site - majority lodged in a culture bank
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Knowledge Gaps - Current Research Status
Ecology of pine stumps - competition between
decay fungi
Armillaria novae-zelandiae throughout (2 genets)
A. novae-zelandiae left, and decay fungus HH
Pine thinning stumps, 200-250 weeks
Prospective testing cultures against
Armillaria in laboratory and field
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Knowledge Gaps - Current Research Status
Variation in host genetic resistance
Pathogenicity testing of pedigree radiata pine
clones (cuttings)
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Knowledge Gaps - Current Research Status
Variation in host genetic resistance
Early provisional result cuttings killed (of 10)
Clone code Isolate 1 Clone code
Isolate 2 E 20 a E,K
50 a F 30 a A,C 60
a D, H 40 ab H, D 70
a C, G, K 50 ab B, F
80 a A 60 ab G, J 90
a B, J 90 b
Ongoing repeat experiment, and expand programme
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CONCLUSIONS
Armillaria has potential for continued
significant national cost
Cryptic Armillaria widely distributed through NZ
and within many pine stands
Potential for increased impact with changes in
management
Identification of areas requiring treatment
appears realistic, eg. by remote sensing
Stump removal as an effective control is not
practiced
However, current research suggests there may be
potential no-extra-cost alternatives
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THANKYOU