Gun Lake Budworm Presentation Sep 3 2012

7/31/2019 Gun Lake Budworm Presentation Sep 3 2012

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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


11/43Chronic 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

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Gun Lake Budworm Presentation Sep 3 2012

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