Extension Note BC Journal of Ecosystems and Management British Columbia’s Northern Interior Forests Warren Root Collar Weevil Stand Establishment Decision Aid

Larry McCulloch1, Brian Aukema2, Ken White3, and Matthew Klingenberg4 Introduction Warren root collar weevil (Hylobius warreni) is a commonly occurring insect found in most of British Columbia and as far north as the Northwest Territories. This weevil affects many tree species and is found in forest stands of any age, although its impact as a disturbance agent is most important in lodgepole pine stands. Engelmann and white spruce are also common hosts, but incidence levels have not been high enough with these species to cause reforestation issues. Incidence levels in lodgepole pine stands commonly exceed 30%, although mortality levels are generally far less and occur in younger stands (5–20 years of age). Recent research suggests that a link exists between stands affected by mountain pine beetle (MPB) and root collar weevil. In one study, the incidence of weevil-attacked trees was elevated in young plantations adjacent to mature stands that had sustained high levels of MPB-caused mortality. An understanding of the weevil’s biology and the identification of high-hazard stand conditions for both insect species are essential to successfully avoid regeneration issues. Most treatments involve mitigation measures applied during stand establishment. The Stand Establishment Decision Aid (SEDA) format has been used to extend information on a variety of vegetation and forest health concerns in British Columbia. The two-page SEDA presented in this extension note was developed to summarize information that northern forest managers will need to manage the impacts of the Warren root collar weevil. The following pages describe susceptible stand types, weevil biology, hazard ratings, forest productivity considerations, and appropriate management practices. A resource and reference list that readers can use to find more detailed information is also included. Most reference material that is not available online can be ordered through libraries or the Queen’s Printer at: www.qp.gov.bc.ca Acknowledgements The preparation and publication of this decision aid was supported by the British Columbia Ministry of Forests and Range through the Forest Investment Account–Forest Science Program. We thank Herb Cerezke and two other anonymous reviewers for their reviews of this SEDA. keywords: duff reduction strategies, Hylobius warreni, lodgepole pine pests, managing pine plantations, pest hazard ratings, stem girdling, Warren root collar weevil. Contact Information 1 Principal, LM Forest Resource Solutions Ltd, PO Box 880, Smithers, BC V0J 2N0. Email: [email protected] 2 Canadian Forest Service, University of British Columbia, 3333 University Way, Prince George, BC V2N 4Z9. Email: [email protected] 3 Forest Entomologist, BC Ministry of Forests and Range, Northern Interior Region, Regional Service Centre, Bag 6000, 3333 Tatlow Road, Smithers, BC V0J 2N0. Email: [email protected] 4 (Formerly Auxiliary Forest Health Technician, BC Ministry of Forests and Range), Unit 3, 800 Second Avenue North, Williams Lake, BC V2G 4C4. Email: [email protected]

JEM — Vo l u me 10, Nu m b e r 2 Published by Forrex Forum for Research and Extension in Natural Resources McCulloch, L., B. Aukema, K. White, and M.JEM Klingenberg. — Vo l u me 2009.10, N Britishu m b e rColumbia’s 1 northern interior forests: Warren1 Root Collar Weevil Stand Establishment Decision Aid. BC Journal of Ecosystems and Management 10(2):105–107. www.forrex.org/publications/jem/ISS51/vol10_no2_art8.pdf mcculloch, a u k e m a , w h i t e , and klingenberg

to

on

by root

evidence planting of

spacing

may

moderate levels

alternate moderate

a

planting delay or duff

during

with had

mounds

increasing

high assessment

is on collar

as reduce

delaying

subzones, to

fill-plant

root there

previously

general rated

a the

seedlings

are that

hazard consider

stocked,

Interior,

that

areas around

scarification high,

conduct

weevil

planting

or

soil units not

and is high areas,

marginally Columbia

to harvested

is

burning

in mineral

hazard hazard

British

stand stems per hectare in anticipation of higher than usual usual than higher of anticipation in hectare per stems

years

the high biogeoclimatic moderate

the brush

that higher levels of weevil incidence in young pine stands stands pine young in incidence weevil of levels higher that when the attack MPB becan expected after years a few attack occurs in adjacent mature stands. Several treatment Several stands. treatment mature occurs in adjacent attack levels high incidence where situations for exist considerations expected. are collar weevil levels in the mature stand to be harvested and in be to harvested and stand weevil in the mature collar levels types. pine mature adjacent hazard for root collar weevil, consider designing cutblocks cutblocks designing consider weevil, collar root for hazard of out migration that so types pine the of all include that pronounced. less is stands mature adjacent 2–3 high hazard rating for root collar weevil. Newly planted trees trees planted Newly weevil. collar root for rating hazard high of diameter collar root a have they until attacked be not will 2 cm. about to adjacent edges cutblock along species susceptible less a cutblock. the within or stands pine mature preferred weevil habitat (moist sites with a substantial duff duff substantial a with sites (moist habitat weevil preferred infestation delay and levels population adult reduce may layer) larvae affect to unlikely is burning Light stands. adjacent from because they occur under the bark. and deeper the duff within decrease mortality levels because this treatment reduces duff duff reduces treatment this because levels mortality decrease collar. the root around levels moisture and is also an option to discourage weevil attack. Weigh the merits Weigh weevil attack. discourage to also option is an humus of removal that the possibility against this treatment of affect seedlingsurvival will adversely and growth. horizons 1600 in earlier also result may density stand Higher mortality. larvae retards which shade, increased and closure crown collar. the root at temperatures lowering by development old. 20 years least at is the stand until species and delay declaring free growing until re-survey is is re-survey until growing free declaring delay and species complete. Management considerations Management • In Harvesting • In • In Stand establishment • If • high, establish were in the harvested stand levels incidence If • Broadcast • Disc-trenching • Exposing • than greater to density planting increasing Consider Plantation maintenance • In • If

adults Klingenberg Matthew

these

and lower

that

to

stem

hatching

suggests

the

after

up

research

summer

crawling Past ) zone, ) zone,

third bec

night,

the

at 1

flightless.

in

are feed

occurs

weevils weevils

Pupa and characteristic resin exudate on a root. climatic conditions. If a biogeoclimatic unit is not listed, root collar collar root If a biogeoclimatic unit is not listed, conditions. climatic be a significant to hazard. weevil is not considered Pupation branches. small of sapwood the into chew they where branches host new for searching when year per m 10–13 migrate insects movement that experimental evidence suggests Recent trees. large a contains habitat the when greater much be can rates dead trees. of proportion emerge in the fall or the following spring. in the the fall following or emerge collar. root the at mass sticky a form to bark and soil with mixed in overwinter and the exudate from Larvae shelters tubelike build these. 3 years. a period to up over of their development See Meidinger and Pojar (1991) for for (1991) Pojar and See Meidinger Biogeoclimatic of explanation an ( Classification Ecosystem abbreviations. variant and subzone,

Ratings are based on expert opinion, known insect biology, and current and current known insect biology, expert based Ratings on opinion, are

1 Hazard ratings • Adult • which is exudation, the larvae pitch by activity causes Feeding • complete may stumps harvest, cut larvae on living Following • Adult a Matthew Klingenberg Matthew

first

litter” extent,

mature them bark

the

the twice.

“kitty lesser

while a

often

of

into is to

depositing

larvae

and, bore trees

two

red

pine then overwintering appearance

or

summer,

the

dead, one the

weeks

in 2 mature,

have

lodgepole

to

eggs support

scattered about

lay years

of in

include only

2

formations

take hatch trees

females

species

pitch presence

larvae a on more or Three more. 30 or support can trees mortality. cause to likely are tree young mixed with soil. with mixed the of the circumference around feeding cambium, and collar. the root at tree at the root collar in chewed bark niches, and in adjacent adjacent in and niches, bark chewed in collar root the at and soil. duff indication that weevils are present in a stand. present weevils are that indication weevil presence. indicate with mixed often resinosis, for looking and collar root scars. feeding and tunnels larval of presence the and soil, The coarse-textured soils and a deep organic duff layer are are layer duff a deep organic and soils coarse-textured susceptible. most generally and may be re-attacked periodically stand to through be re-attacked may and maturity. Engelmann and white spruce, and western white pine. white western and spruce, white and Engelmann • Larvae • Young • 5 years. to up live weevils may Adult • Larvae • also leaders may short and trees fading or green Leaning • the at the duff removing be by can confirmed Infestation Biology • Adult Characteristics of susceptible stands • Host Adult root collar weevil. • The with • sites moister on trees co-dominant and Dominant • age of 5 years at susceptible becomes Lodgepole pine Warren Root Collar Weevil – Northern Interior Forest Region Northern Interior – Collar Weevil Root Warren

106 JEM — Vo l u me 10, Nu m b e r 2 warren r o o t collar weevil–northern interior f o r e s t r e g i o n ociety ociety S esources esources R esearch and and esearch R atural atural N uite 702, 235 1st Avenue, Avenue, 1st 235 702, uite S , , Forum for for Forum The underground plantation menace. plantation menace. The underground nternet without the written consent consent written the without nternet

I Pest impacts in spaced and pruned impacts stands in spaced Pest xtension in in xtension Forrex

E Forrex g esearch and and esearch R ditor, Editor, Managing Production of this article was funded, in part, by the Production of this article was funded, in part, by British Columbia Ministry of Forests and Range through the Forest Investment Account–Forest Science Program. Forum for for Forum esources Society, the Province of British Columbia, and Her Majesty Majesty Her and Columbia, British of Province the Society, esources R February 20, 2009 Forrex V2C 3J4, or email [email protected] email V2C 3J4, or : april 23, 2009 : does not warrant their accuracy or reliability, and expressly disclaims any liability liability any disclaims expressly and reliability, or accuracy their warrant not does contact: consents, . For 1488-4674. Articles or contributions in this publication may be reproduced in electronic electronic in reproduced be may publication this in contributions or Articles 1488-4674. Forrex Forrex xtension in Natural Natural in xtension issn © 2009 Copyright in this article this is© 2009 Copyright in property the of E esources Canada, Canadian Forest Service. Forest Canadian Canada, Resources Natural Canada, Queen of the right in not-for- and training, educational, in recipient the to charge of use free for form print or However, acknowledged. fully are authorship and source their that provided activities profit use other any or media, or forms other to application translation, adaptation, reproduction, the requires redistribution, or resale, use, commercial for part, in or whole in works, these of of consent written BC Kamloops, and of all contributing copyright owners. This publication and the articles and contributions contributions and articles the and publication This owners. copyright contributing all of and the over public the to accessible made be not may herein of The information and opinions expressed in this publication are those of the respective authors arethose ofauthors in thethis expressed and respective publication opinions Theinformation and thereto. relation in British Columbia. 2nd edition. Canadian Forest Service and BC Ministry of Forests, Victoria, Victoria, Service and BC Ministry Forest Canadian of 2nd edition. Forests, British Columbia. 17. No. II Report FRDA BC. of Journal Society the Entomological of in British Columbia. BC 63:3–6. warreni Wood H. 2. No. Report Research Region. George Prince BC Ministry of Forests, AB. Edmonton, Forestry Centre, Northern Forestry Canada, ofAlberta. Foothills west-central NOR-X-330. Report Information Natural MSc thesis, weevil. collar root Warren impacted by beetle replantings and adjacent of British Columbia, Northern University Program, Studies and Environmental Resources BC. George, Prince report. Unpublished BC. Kamloops, BC Ministry of Region. Forests, Forest in the Kamloops m (Accessed www.for.gov.bc.ca/hfd/pubs/Docs/Srs/SRseries.ht 6. Special Series Report No. BC. February 2009). lodgepole pine in north-central naturallymortality regenerated British versus in planted 36:2642–2653. Research of Journal Canadian Forest Columbia. article received article accepted Henigman, J., T. Ebata, E. Allen, J. Westfall, and A. Pollard. 2001. Field guide to forest damage in damage forest to Field guide 2001. Pollard. A. and Westfall, J. Allen, E. Ebata, T. J., Henigman, The hosts and distribution and of (Couper) pinicola weevils collar 1966. Hylobius the root J. Grant, weevil: collar Warren’s 1981. Coates. and H.G. L.J. Herring, affecting the survival Factors of lodgepole pine in the 1993. immature Rentz. and C.L. W.G.H. Ives, pine mountain impacted by associations forests Spatiotemporal between 2008. M.D. Klingenberg, forestry: Enhanced 1998. Brooks. and J. L. Maclauchlan, Victoria, BC Ministry of of British Ecosystems Columbia. Forests, 1991. Pojar. and J. D. Meidinger, and stability, form growth, and root between Relationship 2006. Lindgren. and B.S. J.A. Robert,

or The

new

were

are

sensitive

seek press

with

the

trees to

damage. Alberta

on more

snow

is

and Large to

decrease

migrate

to

tree

following

chewing) roots.

the however,

(or tends

weevils Columbia

lateral

adult

growth, stands

feeding British

immediately

larger

in that by

predisposing

the young

years Leader

tree

to

in stems

the them,

implies the

70%.

in shift

This to

girdled

girdle

mortality weaken

exceeds

10–30% or tends

that

attack. The

by

kill Ecology, behavior, damage relationships, and management. and management. relationships, damage behavior, Ecology, partially

MPB larvae girdling on

MPB.

can feeding

by

by of

declines

until since

roots

area and

on

caused time

reductions

affected the is

affected

injury

trees, damage

growth heavily

damage

increasing

older girdling

BC Ministry of Forests, Kamloops, BC. Kamloops, BC Ministry of Forests, in Canada: Curculionidae), Entomologist 126:(6)1383–1442. Canadian Pest Forest BC. Victoria, and BC Ministry Forestry Canada ofColumbia. Forests, 73. No. Leaflet BC. Victoria, Service and BC Ministry Forest Canadian ofin British Forests, Columbia. 16. No. I Report FRDA Regenerating British Columbia’s forests. D.P. Lavender, R. Parish, C.M. Johnson, G. G. Johnson, C.M. Parish, R. Lavender, D.P. forests. British Columbia’s Regenerating BC. Vancouver, UBC Press, (editors). Winston and D. Willis, R.A. Vyse, A. Montgomery, reported to range from 10 to 30% in the years immediately following damage. following immediately 30% in the years 10 to from range to reported rot. root tomentosus hosts when food supply is reduced by MPB. Populations rarely reach levels that require require that levels reach rarely Populations MPB. by reduced is supply food when hosts these increasing on studies longer-term but planting, of 7 years within intervention complete. yet not are trends mortality study One rare. are 10% exceeding levels Mortality pockets. localized in except stocking, showed zone Cedar–Hemlock District in the Interior Forest in the Kispiox 30 cutblocks of accumulated but weevil, collar root by attacked were pine planted of 39% average, on that, 8.8%. 0 to varied from cutblocks in individual mortality tree increasing distance from the stand edges. Mortality increases with increasing pine pine increasing with increases Mortality edges. the stand from distance increasing and mortality, pine mature of percentage increasing with stands, mature in composition with seldom girdled. seldom a stand. unsalvaged mature, to whenadjacent highest directly weevils generally was by caused stands windthrow. leader length appears to decrease in proportion to the amount of stem girdling. stem of the amount to decrease in proportion to leader appears length to phloem and outer sapwood at the root collar. Stem radial growth does not seem to be to seem not does growth radial Stem collar. root the at sapwood outer and phloem significantly • weevil collar and between exist root may association an evidence that some is There a serious effecthad on weevil not collar has root by caused damage • recently, Until • Height trees. co-dominant • and dominant weevils old), seem prefer to (5–20 years stands young In • throughout scattered randomly small groups occurs usually or trees single as Mortality stands in young mortality that • showed Interior in the central sites nine of study A recent • In • Feeding Resource and Reference List Resource Health, Forest Region, Kamloops insect pests damage. and their Forest 1998. Anonymous. (Coleoptera: Wood warreni Hylobius weevil, collar root Warren 1994. H.F. Cerezke, weevils of and root-collar lodgepole pine in British Terminal 1986. R.W. Duncan, pests of to Field guide managed forest 1989. Hawkins. and G.V. Humphreys, P. K., Finck, In pests Insect in reforestation. 1990. Summers. and D.W. Shrimpton, G.M. K.E., Finck, • weevils. adult by directly caused is damage Little • Most Damage and impact on productivity Damage and Warren Root Collar Weevil – Northern Interior Forest Region Forest Region Northern Interior – Collar Weevil Root Warren

JEM — Vo l u me 10 Nu m b e r 2 107 Test Your Knowledge . . .

British Columbia’s Northern Interior Forests: Warren Root Collar Weevil Stand Establishment Decision Aid

How well can you recall some of the main messages in the preceding Extension Note? Test your knowledge by answering the following questions. Answers are at the bottom of the page.

Significant plantation damage resulting from root collar weevil has not been common historically, but recent indirect evidence suggests that this might change in the face of new climate patterns. Here are a few questions to test whether your current level of knowledge leaves you prepared to recognize and deal with potential problems that might arise as a result of this insect.

1. Lodgepole pine trees of any age can host root collar weevils. a) True b) False

2. Which symptoms are not characteristic of root collar weevil? a) Pitch-soaked frass and soil at the root collar b) Scattered red trees in a stand c) Resin on the lower stem d) Shortened leader growth e) None of the above

3. Root collar weevils prefer the smaller, weaker trees in a stand. a) True b) False

4. In high hazard root collar weevil areas adjacent to a mature stand with high levels of dead trees resulting from MPB attack, it is best to: a) Plant large stock at wide spacing immediately to get a head start before weevils get into the plantation b) Plant more than 1600 stems per hectare c) Intermix a less susceptible species with pine even if it isn’t as well suited to the site ecologically d) Leave an unplanted buffer strip e) Disc-trench and plant seedlings on mounds

ANSWERS

1. A 2. C 3. B 4. B and E 2 JEM — Vo l u me 10, Nu m b e r 1