Forest Insects and

Diseases

White Sulphur Springs

Forest Management Seminar

Amy Gannon

January 2012

Western Spruce Budworm

Amy Gannon

MT DNRC

Forest Pest Management Program

Western Forest Conservation Association

2016

Defoliators

Feed on foliage

Reduce food-making capacity of tree

Not necessarily tree killers

Predispose tree to bark beetles

WSBW Hosts

Douglas-fir

Spruce

Grand fir

Subalpine fir

Larch

WSBW Life Cycle

Four developmental stages:

Egg

Caterpillar

Adult

Pupa

BC Ministry of Forests

BC Ministry of Forests

William M. Ciesla

Jed Dewey

WSBW Life CycleJa

nu

ary

Fe

bru

ary

Ap

ril

Ma

rch

Ma

y

Ju

ne

Ju

ly

Au

gu

st

Se

pte

mb

er

No

ve

mb

er

Oc

tob

er

De

ce

mb

er

Larvae

Larvae

Eggs

Pupae

Adults

Larval Instars

6 instars

Reference handout!

WSBW Identification

Distinct larvae

Chewed needles

Silken clusters

Persistent pupal cases

At least one life stage present

Scott Tunnock

WSBW Identification

Indicative cream-color dots at fourth instar

Emerge in spring – mine buds

May feed in developing cones

Feed primarily on new growth

WSBW Impact - Immediate

After 2-3 years:

Decreased radial

growth

Branch dieback

After 4-5 years:

Top-kill

Understory mortality

Cone crop destruction

Predispose to DFB

WSBW Impact - Recurring

WSBW Damage

WSBW Damage

Stand Composition:

Pure host species

Stand Structure:

Multi-storied, dense

Site Climate:

Warm, dry

Fire suppression history?

Site Characteristics

WSBW Distribution

Regional Climate

Regional temperature + precipitation patterns

4 class divisions based on frequency

Acres Impacted by WSBW

MT Distribution - 2015

1,207,832 acres

WA Distribution – 2011-2015

2015 = 79,000 acres

Create single layer canopies

Intermediate treatments

(fire, thinning)

Promote vigor

Diversify tree species

WSBW Management

Phenotypically superior trees

Budburst phenology:

later = less defoliation, smaller

females

Soluble N = limiting factor in

insect development

Terpenes drastically impact

development

Biotic Controls

Predation

Viral outbreaks

Abiotic Controls

Weather most influential

Unseasonable frosts in

spring or fall

WSBW – Natural Controls

Caution:

Cool, wet springs can simply delay development

Monitor instars!

High value sites:

seed orchards

home sites

recreation areas

Various options:

carbaryl

Btk

insect growth regulator

Protection is NOT long term!

Chemical Controls

Label is the law!

Aerial vs. ground

Systemics vs. topical

Annual reapplication

Will not stem outbreak

Recommend certified

applicator

Insecticide Application

Trade name Sevin

Neurotoxin

Non-target impacts

aquatic invertebrates

pollinators!

pH sensitivity

Careful application

Apply to foliage

Insecticides - carbaryl

Bti = mosquito control

Btt = leaf-feeding beetle

Btk = butterflies, moths

Insecticides - Btk

Naturally occurring in soil

Pest in silkworm colonies

Dipel = oil-based

Foray = aqueous

Treat early instar

Must be ingested

Need foliage to catch spray

Persists for 3-7 days

Insecticides - Btk

Insect Growth Regulator - interferes with molting process

Larvae stop feeding within 24 hours

Specific to lepidopterans – butterflies, moths, skippers

Active ingredient = tebufenozide

Trade name = Mimic (Valent Biosciences Corporation)

Registered for forest use – because the label matters

Apply to 4th - 5th instar larvae

Insecticides - IGR

Questions?