File Report - Not for publication

Forest Insect andDisease Conditions

Cariboo Forest Region1984

R.J. Andrews

Government Gouvernementof Canada du Canada

Canadian ServiceForestry canadien desService forêts

TABLE OF CONTENTS

Page

SUMMARY

1

PINE PESTS

5

Mountain pine beetle 5

Dwarf mistletoe 15

Pine needle casts 17

Blowdown 17

SPRUCE PESTS 17

Spruce beetle 17

Two-year cycle spruce budworm 18

ALPINE FIR PESTS 18

Balsam bark beetle 18

DOUGLAS-FIR PESTS 18

Douglas-fir beetle 18

Western spruce budworm 18

Douglas-fir tussock moth 21

Douglas-fir needle cast 21

HEMLOCK PESTS 21

Western hemlock looper 21

MULTIPLE HOST PESTS 25

Black army cutworm 25

Black vine weevil 26

Pests of young stands 26

SUMMARY

This report outlines forest insect and disease conditions in

the Cariboo Forest Region in 1984, and attempts to forecast pest

populations with emphasis on pests capable of sudden damaging

outbreaks. Pests are listed by hosts in order of importance.

The area of lodgepole pine killed by mountain pine beetle

covered 381 000 ha in 1984. Dwarf mistletoe infection intensities were

rated with mountain pine beetle-killed trees in lodgepole pine stands

throughout the western portion of the Region. Severe winds in Aprilcaused extensive blowdown in pine stands from Anahim Lake to Riske

Creek. In many instances downed trees were infected with a heart rot

and showed advanced decay. Pine needle diseases were conspicuous in

many areas but not as widespread as in the previous two years.

The incidence and extent of spruce beetle-killed mature spruce

decreased for the second consecutive year in the northeast portion of

the Region to 2 200 ha in Bowron Lake Provincial Park and 1 300 ha in

the Big Valley-Ketchum Creek area. Light defoliation of white spruce

and alpine fir by two-year cycle spruce budworm decreased to 200 ha

near the junction of Big Valley Creek and Willow River.

Alpine fir killed by the balsam bark beetle declined to 445 ha

in the south Chilcotin near Taseko, Chilko and Tatlayoko lakes and at

two locations in Bowron Lake Provincial Park.

Mature Douglas-fir killed by Douglas-fir beetle were recorded

by aerial surveys over 1 300 ha. Tree mortality was common along the

Fraser River from Dog Creek north to McLure and south of Alexis Creek.

The area of Douglas-fir defoliated by western spruce budworm near

Clinton increased slightly to 18 800 ha from 18 500 ha in 1983, butdefoliation intensity decreased. Douglas-fir tussock moth populations

in stands south of Clinton collapsed. Most trees which had been

completely defoliated in 1983 showed a successful 1984 year's growthand will likely recover. Douglas-fir needle cast was more widespread in

1984, causing up to 80% needle loss in areas severely infected in thepast two years.

High populations of western hemlock looper lightly to moderate-

ly defoliated 5 250 ha of old growth western hemlock and cedar alongthe north shore of Quesnel Lake for the first time since 1946.

Black army cutworm lightly damaged Douglas-fir seedlings in two

plantations and a provenance trial area near Mitchell Bay and AntoineLake.

Five pheromone-baited gypsy moth traps were set out at each of

three locations in the Region in 1984; no insects were trapped.

The Forest Insect and Disease Survey field season extended from

May 20 to August 4. Special surveys to appraise bark beetle and

defoliator infestations were conducted from September 7 to 20 and

October 15 to 18. A total of 150 insect and disease collections were

submitted to Pacific Forest Research Centre by the Regional Survey

Technician and personnel from B.C. Ministry of Forests. Twelve masscollections of western spruce budworm and western hemlock looper larvaewere examined for disease and parasitism. Locations where one or more

insect or disease samples were collected are shown on Map 1.

Forty-two hours of fixed-wing flying were funded by the

Canadian Forestry Service and B.C. Ministry of Forests in July to mapbark beetle and defoliator infestations west of the Fraser River near

Clinton, in the Cariboo and Quesnel lakes area and in Bowron Lake

Provincial Park (Map 2).

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CARIBOO FOREST REGION0 20 40 km11111

CANADIAN FORESTRY SERVICE/FOREST INSECT AND DISEASE SURVEY

••• A • •

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Map 1. Locations where one or more forest insect and disease samples were collected in 1984

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CARIBOO FOREST REGION0 20 40 kmL I ) )

CANADIAN FORESTRY SERVICE / FOREST INSECT AND DISEASE SURVEY

Map 2. Area covered by aerial surveys, 1984

5

PINE PESTS

Mountain pine beetle, Dendroctonus ponderosae

An estimated 381 000 ha of recently killed pine and 144 000 ha

of pine killed prior to 1982 were mapped during aerial surveys,

slightly less than in 1983 (Map 3). This decline was attributable in

part to the variation among the increased numbers of people contribu-

ting to the sketch mapping in 1983. However, areas of recent treemortality expanded northward to Anahim Lake and Nazko. Up to 80% of the

stands south of Chilcotin Lake east to Palmer Lake and south to Taseko

and Tatlayoko lakes were killed. Infestations intensified between

Chilko Lake and Big Creek north to Clusko River and from Churn Creek,

west of the Fraser, to Gaspard Creek, northward from the Clusko River

and Palmer Lake area to Nazko and Anahim. Tree mortality was sporadic

east of the Fraser River to Horsefly and in the Big Bar Lake-Dog Creek

area and increased slightly in area in the Cariboo Lake drainage.

Spring brood assessments in 1983-attacked trees indicated

generally increasing populations despite high overwintering mortality

(Table 1). A 15 x 15 cm bark sample was removed at dbh from the northand south sides of each of 20 trees per location, the number of larvae,

pupae, teneral adults and entrance holes counted and "R values"'computed for each sample area.

1 'R' value is the average ratio for the 20 trees at a location:

'R' value = number of eggs + larvae + pupae + adults

number of galleries originating in sample

go0 20 40 kmI Ill!

CANADIAN FORESTRY SERVICE / FOREST INSECT AND DISEASE SURVEY

Recently killed trees

0 Killed prior to 1982

CARIBOO FOREST REGION

Map 3. Areas of lodgepole pine recently killed by mountain pine beetle, determined by aerial surveys, 1984

Table 1. 'R' values and 1984 population

Region, June, 1984.

predictions, Cariboo Forest

Location

Average

"R"1

values

Population

prediction

dbh no. larvae/ no. galleries

(cm) 30 cm sample per sample

Km. 43 Palmer L. Rd. 31.1 19.6 1.5 12.9 IncreasingGaspard Cr. - - - 12.8 IncreasingPuntzi Lake 26.5 13.1 1.1 12.5 IncreasingKm. 40 Honolulu Rd. 33 18.8 1.5 11.9 IncreasingKm. 111 Redstone - 19.4 1.9 10.2 IncreasingKm. 17 Chilko R. Rd. 24.1 6.2 1.3 4.5 IncreasingCochin Lake 23.6 8.5 1.9 4.4 IncreasingMichel Cr. (Nazko) 36 6.4 1.4 4.3 IncreasingDean R. 27.4 3.7 1.3 2.8 StaticAlexis Lake 25.8 2.6 1.4 1.8 DecreasingMathew R. 36 1.5 2.3 0.6 Decreasing

12.5 and less = decreasing populations2.6 to 4.0 = populations static4.1 plus = populations increasing

At 5 of the 11 locations, primarily west of Alexis Creek where

'R' values averaged less than 4.5, 50% of the broods had not developed

beyond second instar and an additional 25% had died in the egg stage.

Larval galleries in these instances were nonexistent or less than 1 cmin length, indicating a prolonged attack period in 1983, a higher

incidence of overwintering mortality and a decreased attack intensityin 1984.

Infestations are described by Timber Supply Areas (TSA) and

Supply Blocks (SB) (Map 4, Table 2).

CARIBOO FOREST REGION0 20 40 km

1 1 1 1 1

CANADIAN FORESTRY SERVICE FOREST INSECT AND DISEASE SURVEY

Map 4. B.C.M.F. timber supply areas and supply blocks

Williams Lake TSA Quesnel TSA 100 Mile TSA

1. Anahim S.B. 14. South Kluskus S.B. 23. Meadow S.B.

2. Tatla S.B. 15. West Narcosli S.B. 24. Loon S.B.

3. Chilcotin S.B. 16. East Narcosli S.B. 25. Bonaparte S.B.

4. Chezacut S.B. 17. SSA S.B. 26. Holden S.B.

5. Palmer Lake S.B. 18. Cottonwood S.B. 27. Sheridan S.B.

6. Kloakut S.B. 19. Big Valley S.B. 28. Rail S.B.7. Springhouse S.B. 20. Bowron S.B. 29. Ruth S.B.

8. Churn S.B. 21. Cunningham S.B. 30. Canim S.B.

9. Gaspard S.B. 22. Bowron Unreg. S.B.

10. Skelton S.B.

11. Moffat S.B.12. Upper Horsefly S.B.

13. Cariboo S.B.34. Junction S.B. Provincial Parks

31. Tweedsmuir Park

32. Bowron Lake Park

Federal Lands

33. Military Block

WILLIAMS LAKE TSA

Anahim S.B.: The area of recently killed lodgepole pine declined

overall to 22 800 ha from 34 000 ha in 1983. In Tweedsmuir Provincial

Park, mortality continued on 4 500 ha along the Atnarko River with

patches of 1 to 5 ha into the Bella Coola River drainage to Hagensborg.Scattered patches of 1 to 70 ha were seen north of Anahim along the

Dean River to Hump Creek, west of Anahim along Christensen and

Corkscrew creeks, south of Anahim in the Nimpo Lake area, and east

along Holte and Holtry creeks. The area of pine killed prior to 1982

(grey) was 56 770 ha, mostly in the Charlotte Lake, Upper McClinchy and

Kleenaklini drainages.

Tatla Lake S.B.: Recent tree mortality declined overall to 60 450 ha

from 105 000 ha in 1983, but increased north of Tatla Lake in the

Puntzi, Jergensen, Knoll and upper Palmer creeks drainages.

The area of pine killed prior to 1982 (grey) was 65 000 ha, mainly westof Tatla and Eagle lakes south to Choelquoit Lake and east to Chilkoand Taseko rivers.

Chilcotin S.B.: The area of tree mortality, 7 040 ha, increased in the

Konni-Vedans lakes area and decreased along Taseko, Chilko andTatlayoko lakes.

The area of pine killed prior to 1982 was 2 730 ha.

10

Chezacut S.B.: Recent pine mortality increased to 87 480 ha from 77 750ha in 1983 and was widespread throughout the southern portion from

Puntzi Lake west to the Sister Hills, northward to Chilcotin andTenapho lakes. Sporadic tree mortality extended into the upper

Chilcotin and Clusko drainages to 1 450 m elevation. Trees killed prior

to 1982 covered 850 ha between Chilanko Forks and Tatla Lake.

Kloakut S.B.: Tree mortality increased threefold to 107 400 ha from

36 400 ha in 1983, due to coalescence of many small patches from the

upper Big and Angela creeks northward to the Chilcotin River.

The area of tree mortality attacked prior to 1982 was 12 000 ha, east

of Pyper Lake.

Palmer Lake S.B.: About 27 060 ha of recent tree mortality was mapped

mainly west of Alexis and Summit lakes along the southwest boundary of

the S.B., up slightly from 25 240 ha in 1983. East of the boundary toStum Lake, tree mortality was patchy north to the junction of the Nazko

River and Tautic Creek.

Gaspard S.B.: Increases to 27 100 ha from 16 000 ha in 1983 occurred

mainly in the Gaspard Creek drainage which contained 11 920 ha. Lower

Big Creek contained 8 130 ha; Churn Creek, 5 420 ha, and Farwell Creek,1 626 ha.

Trees killed prior to 1982 were recorded over 2 368 ha.

Churn S.B.: Pine mortality doubled to 8 000 ha from 4 000 ha in 1983

along the upper reaches of Lone Cabin and Coster creeks.

Springhouse S.B.: Pockets of recent tree mortality from Dog Creek to

Williams Lake airport decreased to 4 900 ha from 6 000 ha in 1983. Thedecline was due to logging of infested areas.

Moffat S.B.: About 1 575 ha of mature lodgepole pine were killed in

1984, up slightly from 1 300 ha in 1983. Small scattered groups west ofHorsefly near Beaver Valley and west of San Juan Creek near Enterprise

accounted for most of the mortality.

Junction and Upper Horsefly S.B.: Not covered by CFS aerial surveys.

QUESNEL TSA

South Kluskus S.B.: Small groups of recently killed pine were scattered

over 175 ha along Baezaeko and Coglistiko rivers, up from 1983.

Narcosli West S.B.: Scattered groups of recently killed pine were

observed over 1 735 ha along the lower Baesaeko and Clisbako drainagesto Nazko, down from 4 000 ha in 1983.

11

Narcosli East S.B.: Groups of 1-100 beetle-killed pine were scattered

over 1 280 ha along the Nazko River from Cantillion Creek north to

Marmot Lake and in the upper Snaking River drainage, a decrease from

1 980 ha in 1983.

Cunningham S.B.: A slight increase in the area of recent tree mortality

to 4 230 ha from 3 840 ha in 1983 occurred mainly near Ghost Lake and

along the Mathew River.

100 MILE TSA

Meadow S.B.: Small groups of recently killed pine were observed over

4 880 ha from north and west of the Marble Hills northward through BigBar-Meadow lakes area to the Clink Lake area.

Loon S.B.: Recently killed pine declined from 1 400 ha in 1983, to 9

groups over 350 ha west of the Fraser River near Butcher Creek, one

group over 50 ha near Wohleben Creek and seven small groups over 50 haalong Fiftyone and Fiftyseven creeks.

Holden S.B.: Pockets of 2 to 50 ha containing recently killed pine were

mapped over 625 ha in the Gustafsen Lake, Dog Creek areas, down nearlyfourfold from 2 370 ha in 1983.

Rail, Canim and Sheridan Supply Blocks: Not aerially surveyed by CFS.

12

Table 2. Area and volume of recent mountain pine beetle killed

lodgepole pine as determined by aerial surveys and ground

cruises, Cariboo Forest Region, 1984.

T.S.A. Supply Block Infested area (ha) Volume (m3

)

Williams Lake Anahim 22 810

Tatla 60 450

Chilcotin 7 030

Chezacut 87 490

Palmer Lake 27 060

Kloakut 107 040

Gaspard 27 100

Churn 8 000

Springhouse 4 895

Cariboo 6 590

Moffat 1 570

Skelton 1 540

Subtotal 361 575 7 233 165

Quesnel South Kluskus 180Narcosli West 1 730

Narcosli East 1 280

SSA 10Cunningham 4 230

Subtotal 7 430 148 635

100 Mile Meadow 4 890

Loon 450

Holden 625

Subtotal 5 960 119 275

Provincial Parks and Federal Government Lands

Military Block 240Tweedsmuir Prov. Park 4 530Bowron Lakes Prov. Park 1 650

Subtotal - 6 420

381 385

128 425

7 629 500TOTAL

Cruise strips representative of more recently attacked stands

(Map 5) were established at 20 locations to assess the number andstatus of beetle-killed lodgepole pine (Table 3).

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CARIBOO FOREST REGION0 20 40km11111

CANADIAN FORESTRY SERVICE i FOREST INSECT AND DISEASE SURVEY

Map 5. Locations of stands examined to determine status of mountain pine beetle, 1984

Table 3. Location and status of

Forest Region, 1984.

lodgepole pine in mountain pine beetle infested stands, Cariboo

Percent of trees/ha Average % of volume/haLocation Healthy Current Partial Red Gray Healthy Current Partial Red Gray

Km. 17.5 Taseko L. Rd. 56 19 2 14 9 37 25 2 24 12Km. 30 Taseko L. Rd. 71 16 2 1 0 70 26 2 2 0Km. 40 Taseko L. Rd. 34 47 2 7 10 24 49 2 11 14Km. 6 Gaspard Cr. Rd. 40 39 0 14 7 26 40 0 21 13Km. 6 Mons L. Rd. 35 65 0 0 0 18 82 0 0 0Km. 36 Palmer L. Rd. 58 33 5 1 3 39 51 3 3 4Km. 45 Palmer L. Rd. 44 39 1 7 9 31 48 1 10 1016 Km. S. of Alexis L. 53 34 0 3 10 30 54 0 6 1010 Km. N. of Spain L. 65 22 2 8 3 48 26 1 17 8Km. 111 Redstone Rd. 35 10 0 28 27 23 9 0 37 31Km. 160 Redstone Rd. 76 16 0 2 6 65 29 0 2 4Puntzi L. 40 12 0 42 6 25 11 0 56 8Km. 8 Chilko R. Rd. 51 34 0 11 4 29 35 0 28 8Km. 24 Chilko R. Rd. 35 12 0 28 25 23 12 0 42 23Km. 38 Chilko R. Rd. 75 2 0 17 6 48 6 0 26 20Pyper L. 74 3 0 23 0 56 4 0 40 0Tatla L. 36 27 0 3 34 24 23 0 1 5216 Km. S. of Nimpo L. 88 4 0 3 5 77 4 0 10 9Km. 37 Honolulu Rd. 79 20 0 1 0 66 32 0 2 0

Average 1984 56 24 1 11 8 41 30 4..1 17 11

Average 1983 54 32 5 6 3 41 41 5 10 3

15

Current attack decreased on average to 24% from 32% in 1983,

attributed in part to cold, wet weather conditions which delayed brood

development in the spring and early summer. Based on the information

from fall surveys, however, large populations west of the Fraser River

in the Churn and Gaspard drainages, Big Creek, Mons Lake area and in

the Palmer Lake area will likely increase precluding adverse climatic

factors during brood development in 1984-85. In the Nazko area, of six

locations containing 4 to 50 infested trees, only one with trees of

higher than average volume was attacked in 1984, indicating a general

decrease in the number of scattered infestations in the area. In the

Cariboo Lake-Mathew River infestations populations are expected to

continue to decline.

Lodgepole pine dwarf mistletoe, Arceuthobium americanum

Dwarf mistletoe infections in lodgepole pine stands have

resulted in significant volume losses in many stands in the Region.

Roadside surveys in 1972-1973 indicated that mature pine stands along

39% of the 2 850 km travelled in 9 PSYUS were infected (Van Sickle,

1975) (Appendix 1). Lodgepole pine dwarf mistletoe infected up to 55%of the understory and 43% of the living overstory in 8 mountain pine

beetle infested stands (up to 65% of the mature pine was killed) in the

Chilcotin, where a pilot survey (Shore et al, 1982) was conducted in

1982 to determine the incidence of dwarf mistletoe infection (Table 4).

Table 4. Incidence of lodgepole pine dwarf mistletoe in regeneration

lodgepole pine in the mountain pine beetle infested stands inthe Chilcotin, Cariboo Forest Region, 1982.

Regeneration Pine% infected

Location by mistletoeNo. Average

examined per ha % stocking ht(m) age

Pyper Lk. 2 52 3 467 60 0.5 8Tatla Lk. 0 21 1 400 50 1.7 16Tatla Lk. south 0 37 2 467 55 0.5 10Tatla Lk., 18 Km W. 55 31 2 067 45 5.9 25Horn Lk. Road 0 8 533 20 3.2 15Clearwater Lk. 35.5 62 4 133 60 1.4 24McClinchy R., 8 Km N. 20 40 2 667 65 2.9 28*Anahim Lk. 32 301 820 - 2.6 -Puntchesakcut Lk. 47.5 164 1 650 8.5 -

*10-1/50 ha plots established on a cruise line at each location in 1984.

16

In 1984 a survey to determine the correlation of beetle attack

with incidence and severity of dwarf mistletoe was completed at 27

locations (Table 5). Results showed that there was no apparentcorrelation between the occurrence or severity of dwarf mistletoe with

the incidence of mountain pine beetle attack. Of the 20 stands

examined, 10% were severely mistletoe infected and 56% to 60% of thestems were killed by mountain pine beetle; 55% were moderately

infected, with 20% to 60% beetle-killed, and 35% lightly infected and

12% to 65% of the trees beetle-killed.

Table 5. Dwarf mistletoe infection rating' of living and mountain pine

beetle-killed

Region, 1984.lodgepole pine at 20 locations, Cariboo Forest

Location

Mistletoe infection rating in healthy

Mountain nine beetle attack category

and killed

Average

trees

SeverityHealthy 1984 1983 prior to 1983

Gaspard Cr. 5.4 4.8 6.0 5.1 5.2 SevereKm. 36 Palmer L. Rd. 5.8 5.7 6.0 6.0 5.6 SevereMons Lake 3.6 4.8 - - 4.5 ModerateKm. 17.5 Taseko L. 4.2 5.1 4.9 6.0 4.6 ModerateKm. 30 Taseko L. 4.1 4.6 5.0 - 4.1 ModerateKm. 40 Taseko L. 4.0 4.3 4.8 5.2 4.6 ModerateTatla L. 4.2 2.8 3.0 3.0 3.3 ModeratePuntzi L. 4.1 5.2 3.1 5.4 3.9 ModerateKm. 136 Redstone 3.0 4.2 4.9 3.3 ModerateKm 160 Redstone 2.9 3.5 2.0 - 3.0 Moderate10 Km. N. of Spain L. 3.8 3.7 5.2 4.4 3.9 ModerateKm. 36 Palmer L. Rd. 3.5 4.8 5.6 4.1 ModerateKm 40 Honolulu Rd. 4.5 5.1 5.5 - 4.6 ModerateKm. 8 Chilko R. Rd. 0.7 0.9 1.2 1.1 0.8 LightKm. 24 Chilko R. Rd. 1.1 0.9 0.3 0.3 0.5 LightKm. 38 Chilko R. Rd. 0.9 1.9 1.6 2.3 1.1 LightPyper L. 0.6 0.0 0.3 - 0.5 Light16 Km. S. of Nimpo L. 2.7 3.8 4.0 2.0 2.9 LightKm. 111 Redstone 0.4 0.7 0.3 0.2 0.4 Light16 Km. S. of Alexis L. 2.3 3.1 3.7 2.3 2.6 Light

'Healthy - 0; Light - 1-2; Moderate - 3-4; Severe - 5+

Due to the increasing opening of pine beetle-killed stands,

dwarf mistletoe seed production will probably increase and more seed

will reach understory regeneration. As the regeneration grows, it willpresent a larger target and the probability of infection will increase.

Identification and priorized treatment of beetle-killed dwarfmistletoe infected stands is recommended.

17

Pine needle casts, Lophodermella concolor Dothistroma pini

For the fourth consecutive year moderate to severe discolor-ation of two-year old lodgepole pine foliage by Lophodermella concolor

occurred over widespread areas west of the Fraser River from north of

Riske Creek to Tzenzacut Lake, in the Big Creek area and along theAlexis Lake road. Discoloration in stands east of the Fraser River was

less severe.

Based on the similarity of weather conditions during the spore

dispersal period of early summer, moderate to severe infection is

expected to occur in 1985.

Blowdown

Severe winds in April caused widespread blowdown of mature

lodgepole pine in the Chilcotin and Nazko areas. Downed trees were more

numerous along stand openings, roads, cut blocks, sloughs and openrange. An average of 16 downed trees per kilometre were evident for 10

kilometres along the Chezacut road north of Redstone; 6 stems per Kmnear Puntzi Lake and 40 stems per Km along Palmer Lake road near Km 45,

along the Nazko road from Puntchesakut Lake west to Nazko and from

Chilko Lake north along the Chilko River to Alexis Creek. Sporadic

light blowdown occurred from Big Bar Lake road north of Clinton to 100

Mile House.

There was a high incidence of advanced root and butt rot

infections by red ring rot, Fomes pini and brown crumbly rot, Fomes

pinicola in windthrown trees. Along the Palmer Lake road, 58% of the

windthrown trees were severely infected with 3 to 6 cm sound-woodshells on the lower stems of 25 of 25-30 cm diameter trees.

Severe attacks by engraver beetle, Ips sp., on downed trees

occurred in the Nazko and Puntzi Lake areas in early June. The beetle

does not usually attack standing trees, but high populations can attackand kill pockets of standing trees.

SPRUCE PESTS

Spruce beetle, Dendroctonus rufipennis

The area of mature white spruce killed by recent spruce beetle

attacks in Bowron Lake Provincial Park decreased for the third

consecutive year to 2 200 ha from 4 000 ha in 1983. About 1 300 ha of

recent mortality was reported by B.C. Ministry of Forests in the Big

Valley-Ketchum Creek area.

Populations are expected to remain static or decrease in 1985

based on brood examinations and a declining trend over the past twoyears.

18

Two-year cycle spruce budworm, Choristoneura biennis

About 50% of the current year's buds of mixed age alpine fir

and white spruce were defoliated over about 200 ha in the Big ValleyCreek and Willow River area. Although the area and intensity of

defoliation declined over the past two years, egg counts in Augustaveraged 5 per 100 cm of foliage, which indicates continuing light

defoliation in 1985.

ALPINE FIR PESTS

Balsam bark beetle, Drycoetes confusus

Alpine fir killed by the balsam bark beetle complex was

recorded over 445 ha in the south Chilcotin near Chilko (25 trees),

Taseko (225 trees) and Tatlayoko (50 trees) lakes and at two locations(50 trees) in the Bowron Lake Provincial Park. In 1983, 1 125 killed

trees were counted at these locations.

DOUGLAS-FIR PESTS

Douglas-fir beetle, Dendroctonus pseudotsugae

The area of mature Douglas-fir killed by the beetle in 1984,determined by limited aerial surveys, decreased greatly to 1 320 ha

from 19 000 ha recorded by the B.C. Ministry of Forests in 1983. Thedecrease was due mostly to extensive trap tree programs by the Ministry

of Forests and Industry over the past two years.

Locations of recently killed trees were: Dog Creek, 450 ha;

Meason Creek, 130 ha; Sting Lake, 130 ha; Brigham Creek, 190 ha; Ross

Gulch, 65 ha; Chimney Lake, 165 ha; Military Block, 124 ha and CanoeCreek, 65 ha.

Western spruce budworm, Choristoneura occidentalis

An estimated 18 800 ha of Douglas-fir were defoliated by thebudworm in the Clinton area in 1984 (Map 6) about the same as in 1983.

Severe defoliation occurred over 1 790 ha along the southeast shore of

Loon Lake and along Bonaparte River north of the Loon Creek junction.

Moderate defoliation affected 12 140 ha in the Wohleben Creek drainage,south of Loon Creek, along Hart Ridge and west and north of Clinton

from Cutoff Valley to Big Bar Lake road and Chasm Creek. Lightdefoliation was recorded over 4 870 ha along the east slopes of

Tsilsalt Ridge from Kay Creek to the Cemetery, along the north shore ofLoon Lake and Creek and in pockets along Hart Ridge.

CHILKO

► LAKE

100 MILE •

GANG RANCH

LINTONlb-.Ma...11111111111111W -...••■•■•

WELLS •

NAZKO OUESNEL

Do"OUESNEL

LAKE

LIKELY

ANAHIM LAKE

WILLIAMS LAKE•

ALEXIS CREEK

CARIBOO FOREST REGION0 20 40 km[Ili

C:9 Western spruce budworm

.411/ Western hemlock looper

CANADIAN FORESTRY SERVICE/FOREST INSECT AND DISEASE SURVEY

Map 6. Areas defoliated by western spruce budworm and western hemlock looper, deter-mined by aerial surveys, 1984

The number of larvae in infested buds in June indicated light

defoliation along Big Bar Lake road (where less than 20% of the budswere infested) and moderate to severe defoliation along Hart Ridge and

near Loon Lake (where more than 20% of the buds were infested). Between300 to 400 larvae per beating sample were recorded at each of six

locations in late June, up from 1983.

Parasitism by mainly Glypta fumiferanae and to a lesser extent

Apanteles fumiferanae affected 19% to 43% (average 31%) of the reared

budworm larvae from three areas and 8 to 34% were killed by

undetermined causes (Table 6). However, until biological control agentsaffect at least 70% of the larval population, there is usually little

change in defoliation intensity.

Table 6. Parasitism results of reared early and late instar western

spruce budworm, Cariboo Forest Region, 1984.

Location andlarval instar

No. of larvae

reared

Percentage

Parasitized Dead from Adults

larvae unknown causes emerged

Early instar larvaeN. Hart Ridge 108 27 57 16

Big Bar L. Rd. 134 30 38 32

Loon L. 113 27 29 44

Late instar larvae

N. Hart Ridge 74 39 52 9

Big Bar L. Rd. 134 19 45 36

Loon L. 86 43 57 0

To determine the number of egg masses and predict population

trends and damage potential in 1985, two branches from the mid-crown of

each of 10 trees were collected at four locations in September (Table

7). Results indicate that defoliation is expected to be severe in most

areas similar to or greater than in 1984, precluding overwinteringearly instar larval mortality.

Table 7. Number of western spruce budworm egg masses per 10 m L of

foliage and predicted defoliation of Douglas-fir in 1985,Cariboo Forest Region.

Number of egg masses Predicted defoliation1

Location per 10 m of foliage

1984 1985

North Hart Ridge 192 SevereBig Bar L. Rd. 332 SevereLoon L. 154 SevereWest of Clinton 585 Severe

1Light 1-50 egg masses per 10 m

2 9f foliage

Moderate 51-150 egg masses per 10 m 2 of foliageSevere 151+ egg masses per 10 m of foliage

21

Douglas-fir tussock moth, Orgyia pseudotsugata

The Douglas-fir tussock moth infestation south of Clinton,

which defoliated 500 ha of Douglas-fir in 1982 and 170 ha in 1983,collapsed. The collapse was attributed to severe infection of late

larval populations by a nuclear polyhydrosis virus (NPV) in 1983.

A Douglas-fir stand opposite McKay Creek south of Clinton

severely defoliated in 1982 and 1983, was monitored in 1984 to

determine tree recovery. A total of 63 trees in 8 plots were examined

along a compass line. Tree diameters ranged from 7 to 75 cm; most (65%)

less than 20 cm dbh. Fifty-nine trees were classified as severelydefoliated (67%+ defoliation) and four trees were classified as

moderately defoliated (33% to 66%). New buds developed on all

previously defoliated plot trees and the new flush was lightly

defoliated during June and July by western spruce budworm. Four trees

(12 to 18 cm dbh) showing no current year's flush by September probably

will not survive.

Douglas-fir needle cast, Rhabdocline spp.

The severity and extent of infection increased throughout the

host range for the second consecutive year. Up to 50% needle loss

occurred over 1-50 ha areas of regeneration and pole-sized trees in the

Lac La Hache, Chasm, Alexis Lake and Nazko areas.

WESTERN HEMLOCK PESTS

Western hemlock looper, Lambdina fiscellaria lugubrosa

Western hemlock looper lightly to moderately defoliated 5 000

ha of decadent hemlock-cedar stands below 1 000 m elevation along the

shores of Quesnel Lake (Map 6). The defoliation followed a one-year

population buildup. The largest and most severe defoliation was in theAbbot Creek-Lynx Creek area. Light defoliation occurred in patches

along the south shore from Mitchell Bay east to Boulder Creek.

An average of 185 larvae (range 4-450) per three-tree beating

sample were collected from western hemlock during June and July about

the same as 1983.

The incidence of parasitism in early and late instar larvae

averaged 12% (range 2-22%) (Table 8).

22

Table 8. Incidence of parasitism in western hemlock looper larval

populations, Quesnel Lake area, Cariboo Forest Region, 1984.

Percentage

Location and Larvae Parasitized Died of Emerged

larval stage reared larvae pupae unknown causes adults

Early instar

Abbot Cr. 113 1 11 33 55

Mitchell Bay 143 11 0 34 55

Late instar

Abbot Cr. 216 19 19 26 36

Mitchell Bay 295 12 1 15 72

About 2 300 pupae were collected in bands of burlap sacking

wrapped around the base of 20 mature trees. Approximately 9% were

parasitized by dipterous parasites and 3% by hymenopterous parasites.

Diseases were not present on larvae or pupae.

The low incidence of larval and pupal parasitism is not

expected to have any significant impact in curbing high populations in

1985.

Egg surveys were completed in September to determine the

population potential in 1985. About 43 overwintering hemlock looper

eggs per 100 gram samples of lichen (old man's beard) from each of 10

trees at Abbot Creek were healthy (Table 9).

Table 9. Results of western hemlock looper egg survey near Abbot Creek,

Cariboo Forest Region, 1984.

Healthy Parasitized Sterile Old Lichen wt. (grams)

Total no. eggs

Av. no. eggs/100 grams

Percentage

2 326

47

63

427

8

12

914

18

25

2 573

51

41

5 082

Based on the criteria that: 5-26 healthy eggs per 100 grams of

lichen will result in light defoliation; 27-59 eggs per 100 grams willresult in moderate defoliation; 60+ eggs per 100 grams of lichen will

result in severe defoliation, it may be expected that continuing highpopulations of western hemlock looper will cause moderate defoliationin the Abbot Creek area in 1985.

NN

---

50

40

30

20

I0

I I I 1 I 1 1 1 I

2 4 6 8 10

11 I 1 I I I I I 1

2 4 6 8 10 2 4 6 8 10

23

— — HEALTHY

STERILE

— — PARASITIZED

UPPER MID LOWERCROWN LEVEL

Figure 1. Number of western hemlock looper eggs per 100 grams of lichen by crown level,Abbot Creek, Cariboo Forest Region, 1984

HEALTHY EGGS

UPPER CROWN

MID CROWN

LOWER CROWN

TREES

Cf)2 120crcr

100

cr 80

cLcr) 60

0 40

20

Figure 2. Average number of healthy, parasitized and sterile western hemlock looper eggsper sample, Abbot Creek, Cariboo Forest Region, 1984

24

MULTIPLE HOST PESTS

Black army cutworm, Actebia fennica

Black army cutworm feeding lightly to moderately defoliated

mostly Douglas-fir seedlings at a provenance trial site and two

plantations near Mitchell Bay and Antoine Lake (Table 10).

The most severely affected seedlings were in Blk. 111 at

Mitchell Bay where 74% of the seedlings were more than 50% defoliated

in June. Seedlings at the other two sites were less severely defoliated

and there was little evidence of seedling mortality. Follow-up surveys

to assess survival will be conducted in 1985.

Table 10. Defoliation of conifer seedlings damaged by black

cutworm in four plantations, Cariboo Forest Region, 1984.army

Location

Stock anddate planted

No. of

seedlingsexamined Healthy

% defoliated

No. ofbuds

damaged10% 10-50% 51+%

Mitchell BayProvenance trials 0-fir 1984 260 75 19 4 2 2

Mitchell Bay

adjacent to trials eS 1983 150 88 12 0 0 12

Mitchell BayBlk. 111 south slope D-fir 1984 100 2 7 17 74 2

west slope D-fir 1984 100 95 5 0 0 0

east slope D-fir 1984 100 99 1 0 0 0

Antoine Lake D-fir 1984 108 79 16 5 0

Elsewhere in Blk. 111 and near Antoine Lake, appraisals by

industry indicated up to 50% mortality of Douglas-fir in scattered

patches, mostly in southern exposed areas. Moderate to severe

defoliation was noted over about 8 ha near Antoine Lake, but seedlingmortality was not evident.

In the provenance trial area, numbers of third to fifth instar

larvae per square foot of duff ranged from 0.4 to 2.5. Control measuresimplemented by the B.C. Ministry of Forests reduced populations to 1

larva per square foot in 30 samples compared to 1.6 larvae in 30control samples.

Population fluctuations are difficult to predict but moths from

infested sites frequently migrate or are attracted to sites burned inthe previous two years. When this situation occurs the potential fordamage to recently planted seedlings is greater than in non-burned orolder burned sites.

25

Black vine weevil, Otiorhynchus sulcatus

The weevil was detected in seedling plugs obtained from the

Koksilah nursery in Duncan for planting in the Horsefly area, the firstrecord of the weevil in the area. The weevil is primarily a pest of

nursery stock and is not likely to become established in the area.

Pests of young stands

An estimated 621 immature lodgepole pine in nine 1/50 ha plots

in a 30 ha plantation at Km 21 Palmer Lake Rd. were examined for

insects and diseases. The most common pest, lodgepole pine terminal

weevil, Pissodes terminalis affected up to 6% of the terminals; current

attack was not evident. Western gall rust, Endocronartium harknessii

infected 2% of the stems and less than 1% of the branches and stemrust, Cronartium sp. and a pitch nodule maker, Petrova albicapitana

affected less than 1% of the trees.

26

Appendix 1. Incidence of lodgepole pine dwarf mistletoe

roadside survey in the Cariboo Forest Region.

observed in a 1972

PSYU

Miles travelled % of distance with pine

Total

with pine the

Major species HealthyInfected

Light Moderate Severe

Big Bar 205 54.20 24.5 45.6 19.5 10.4Big Bar 205 54.20 24.5 45.6 19.5 10.4Big Valley 25 6.00 100.0Bowron 45 12.30 100.0

Chilko 230 148.55 7.3 65.3 18.6 8.8Cottonwood 95 16.70 100.0Narcosli 220 143.10 44.6 25.0 16.9 13.5Quesnel Lake 185 41.80 61.5 18.6 9.6 10.3Stum 305 114.15 10.7 46.3 30.7 12.3Williams Lake 185 37.40 32.5 34.7 11.8 21.0

Total or Average 1 780 695.00 28.3 40.6 20.5 10.6

1Healthy, no infected trees; Light, less than 1/3 of trees infected;

Moderate, from 1/3 to 2/3 of trees infected; severe, more than 2/3 of treesinfected.

Canada