gun lake budworm presentation sep 3 2012
TRANSCRIPT
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The western spruce budworm,Choristoneura occidentalis,
in B.C.
Dr. Lorraine Maclauchlan
Forest Entomologist
MFNROKamloops, B.C.
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The western spruce budworm in B.C .
1. Biology of the budworm
2. Impacts and outbreak history in B.C.
3. Why has the budworm been so successful the past
100 years?4. Management strategies and options
Harvest and thinning B.t.k.
5. Private land options: Permits; costs; process
6. Questions and Discussion
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2nd instar overwinterMoths mate
Feeding larva
Eggs
Fall larval dispersal
Spring dispersal& budmining
Summer Winter
Pupa
1.Biology of the budworm
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Family TortricidaeChoristoneura occidentalis
Western spruce budworm Adults are mottled orange brown
moths
Moths disperse and mate in mid-July to early August
Moths are capable of dispersingvery long distances
females lay one egg complementprior to dispersing
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Moth lays eggs on underside of needles ina shingle-like mass
The preferred location for eggdeposition is the upper third of mature,overstory Douglas-fir
1st
instar larvae hatch in 10 days
July to mid-August
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Small larvae disperse on fine
threads over tree canopy and tosmall trees below
Budworm overwinter as 2nd instarlarvae (do not feed) - referred to
as L2s
Hatched egg masses
New egg mass
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Larvae do not feed atthis point spin silken shelters
among lichen and underbark scales
Larvae overwinter inthese hibernacula
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In early summer, larvae emerge fromoverwintering sites (hibernacula) andmine needles or buds
As new shoots elongate &larvae feed more openly -webbing themselves in the
new foliage Larger larvae can back
feed - consuming old &new foliage
June to late-July
Late May early June
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Pupae are seen July-August
Pupa are immobile & donot feed
Moths emerge lateJuly-August, emit sex
pheromone to attractmates
mate and begin layingeggs
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Current year (new) defoliation
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slower tree growth and production in affected stands
topkill and mortality limited management options oncesevere damage is incurred
highest impacts to understory and intermediate trees
>51% of the IDF has a history of WSB defoliation much ofremainingIDF is dominated by pine or pine/fir mixes
WSB outbreak range is expanding. Therefore, harvestingand intermediate treatments must promote more vigorous,resilient and diversified stands (e.g. lower density stands)
2. Impacts and outbreak history in B.C.
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100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
Ha
defoliated
Annual area defoliated by western sprucebudworm in B.C. 1909-2011
Coastal
(sea level)
Coast range
Coast range &
S. Interior
S. Interior &Cariboo
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History of Budworm Spray Programs in B.C(1987-2012)
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
Hectares
Area sprayed (ha)
Area defoliated (ha)
sever y o ou rea arva ens y can n uence spray resu s
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Area Hectares sprayed
Okanagan 26,157
Merritt 24,078
Kamloops 2,919
Cariboo 44,000
Rock Creek 10,000
Total 107,154
Hectares of western spruce budwormtreated with B.t.k. in 2012
sever y o ou rea arva ens y can n uence spray resu sinsect and bud synchrony will determine how much damage is incurred prior to spraying
canopy architecture influences spray deposit and therefore results
operational considerations include block size (ha) and configuration, elevation range of blocks, availability of staging sites, public and
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Map of South Central South East B.C.
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Range of Interior Douglas-fir biogeoclimatic zone
4,481,634 ha IDF in B.C.
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Western spruce budworm defoliation 1909-1995
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Western spruce budworm defoliation 1909-2010
Now >51% IDF has a
history of WSB defoliation
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Historic WSB defoliation and 2011 defoliation
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Coast
Okanagan_NE
Okanagan_SE
Lillooet
Kamloops
Williams Lake
Cental Cariboo
Merritt
VanIsle
Quesnel
Princeton
100 Mile House
Hope
Wells
Vernon
Lytton
Clinton
Osoyoos
KelownaMerritt
Keremeos
Horsefly
Whistler
KamloopsAshcroftLillooet
Pemberton
PrincetonPenticton
Logan Lake
Clearwater
Salmon Arm
Revelstoke
Grand Forks
Alexis Creek
Re-defined Geographic Outbreak Areas of Western Spruce Budworm
120 000ill
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0
50,000
100,000
150,000
200,000
250,000
1909
1918
1924
1928
1944
1949
1955
1967
1971
1975
1979
1983
1987
1991
1995
1999
2003
2007
Ha
defol
iated
Kamloops
0
20,000
40,000
60,000
80,000
100,000
120,000
19
09
19
18
19
24
19
28
19
44
19
49
19
55
19
67
19
71
19
75
19
79
19
83
19
87
19
91
19
95
19
99
20
03
20
07
Ha
de
foliated
Lillooet
dry forests near Lillooethave the longest & mostchronic outbreak historywith 6 distinct outbreaks in
the past century outbreaks range from a few
thousand ha to >100,000 haof annual defoliation
Budworm became adominant force in IDFdkand xh forests aroundKamloops in the late1970s
Kamloops now experiencesextensive, long and oftensevere outbreaks
120 000M i
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0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1909
1918
1924
1928
1944
1949
1955
1967
1971
1975
1979
1983
1987
1991
1995
1999
2003
2007
Chilcotin-Cariboo
0
20,000
40,000
60,000
80,000
100,000
120,000
19
09
19
18
19
24
19
28
19
44
19
49
19
55
19
67
19
71
19
75
19
79
19
83
19
87
19
91
19
95
19
99
20
03
20
07
Merritt
Recent new outbreak area
First large-scaleoutbreaks recorded inthe late 1970s
Merritt now
experiences chronic andoften severe outbreaks
First large-scaleoutbreak recorded inearly 2000s
Outbreaks are severein part due to standstructure and density
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Coast outbreak
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changing, warmer climate in Douglas-fir
habitat fire suppression; harvest of large, old
dominant overstory trees; loss of pine(MPB)
humans have dramatically changed thedensity, structure and composition ofB.C.s inland forests
3. Why has the budworm been sosuccessful the past 100 years?
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Environmental: changing, warmer climate in Douglas-
fir habitat (notably in the spring during L2dispersal and budmining)
Human intervention: fire suppression; harvest oflarge, old dominant overstory trees; loss of pine
(MPB outbreak) all this leading to a structure and canopy
development conducive to budworm success
The insect: the budworm can disperse greaterdistances and still encounter favourable habitat;highly fecund and mobile insect; typicallyscattered, endemic populations are now attainingoutbreak levels over far wider geographic ranges
Imp t f h n in tb k d n mi
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Impacts of changing outbreak dynamics Are host trees conditioned to budworm
(resilience, synchrony)?
Are outbreaks more persistent?
Are impacts more severe?
Stand west of Princeton
assessed impact from budworm defoliation
first defoliated 2002, then 2005-06 and2008-09 (total 5 yrs)
selectively harvested and now multi-layered,predominated by intermediate size trees withpatchy regeneration high hazard tobudworm
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IDFxh2 with a history of 8 years of defoliation
4 M d
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Hazard rate IDF and othersusceptible ecosystems:
stand structure and age
species composition
density (by canopy layer)
elevation and aspect
budworm defoliation history
geographic outbreak area
Define landscape and standlevel goals in high hazardbudworm areas.
4. Management strategies and options Harvest and thinning B.t.k.
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Intermediate stand treatments:
thinning to create stand diversity and lower densityin understory layers ($1,200 - $1,600 per ha)
spray with a biological insecticide (B.t.k.) to reducebudworm populations and minimize damage ($30-$35per ha for MFLNRO).
Harvesting could includeselection cuts; patchcuts; partial cuts; seed
tree cuts
Emphasize diversity andstructural resilience
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Bacilus thuringiensisvar. kurstaki(B.t.k.)
Bacillus thuringiensisis a rod-shaped bacterium thatoccurs naturally on dead or decaying matter in soil.
It was first isolated in 1902 from diseased silkwormlarva.
B.t.var kurstaki (B.t.k.) -highly specific to Lepidoptera(moths and butterflies), withno effect on other insects.
FORAY 48B (B.t.k.)is registered forbudworm and tussock moth.
FORAY 48B is may be used in certifiedorganic production (OMRI)
OMRI=Organic Materials Review Institute
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B.t.k. begins to work after a larva eats a piece of leafwith B.t.k.crystal proteins and spores on it.
When the crystals reach the larvaes gut, they dissolve inthe alkaline conditions (above ~pH 9.5) and release theproteins contained in the crystal.
Larvae cease feeding within about 30 minutes ofingesting B.t.k. -the proteins disrupt the lining of thegut, which causes the caterpillar to starve.
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Humans and other mammals have highly acidicenvironments in their stomachs that destroy B.t.k.before it can causes infection.
Because the B.t.k.endotoxin requires extremelyalkaline conditions to become active (such as thosefound in the guts of caterpillars), B.t.k.does not affectanimals with acidic stomach environments such as birds,
fish, and mammals.
Gypsy moth larvae
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A commercial B.t. product was first registered in theUnited States in 1958; by 1960 it was cleared for useon food crops and in 1961 it was registered for use in
Canada.
B.t. is not a synthetic chemical.
B.t. products contain highly specialized protein crystalsand dormant spores of bacteria.
These are only activated when they are eaten by asusceptible species of insect.
Unlike broad spectrum insecticides, B.t. is highly specificaffecting only certain groups of insects and has no
effect on others invertebrates or animals.
It is now the most widely used naturallyoccurring pest control product in theworld.
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Direct control considerations forWestern spruce budworm
Foray 48B (Bacillus thuringiensisvar.
kurstaki, or B.t.k.)
Whywould you spray?
Wherewould you spray? When would you spray?
Who decides to spray and holds Permits?
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Whywould you spray? reduce resident population of budworm
reduce incremental and height loss
prevent tree mortality
increase tree and stand resiliency
maintain property values
Wherewould you spray? areas with 2 consecutive years defoliation
high value stands (managed, woodlots,recreation)
where tree mortality imminent population
predicted to be high in coming season
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Whenwould you spray?
when levels of predicted tree mortality
becomes unacceptable
when growth loss becomes unacceptable
when fir beetle populations are building
When visual landscape is unacceptable
social and recreational considerations
when perceived fire risk is unacceptable
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Spray Challenges: severity of WSB outbreak (larval density) can influence
spray results insect and bud synchrony will determine how much
damage is incurred prior to spraying
canopy architecture influences spray deposit and
therefore results operational considerations include block size (ha) and
configuration, elevation range of blocks, availability ofstaging sites, public and First Nations considerations,
weather
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Efficacy of a spray program can be evaluated innumerous ways:
Larval mortality (determined through per- and post-spraylarval sampling)
Foliage protection (degree of defoliation to current yearshoots/foliage)
Budworm population suppression usually determined bythe fall WSB population estimates (egg mass sampling) andfollowing year defoliation in the general area of treatment
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Budworm larval density (# larvae per m2 foliage) atthe pre-spray sampling has increased over time:
1987 - average 100 larvae/m2
2012 - average >200 larvae/m2
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stands are more suitable now than 100 yrs ago
budworm is able to reach outbreak levels morefrequently and over expanded ranges
larval and bud phenology are critical to success
better climatic conditions allowing rangeexpansion
impacts can be severe after only a few years ofdefoliation
Recap: