Role of Insects in Forest Ecosystems

Lecture Notes: Forest Insects

ENT/PLPATH/FWE500

Insects and Disease in Forest Resource Management

Kenneth F. Raffa

Dept. Entomology

345 Russell Laboratories

University of Wisconsin

Madison, WI 53706

262-1125

http:entomology.wisc.edu/~ raffa

TABLE OF CONTENTS

Role of Insects in Forest Ecosystems...... 4

Introduction to Entomology...... 6

Classification and Diversity of Insects...... 6

Insect Structure & Function...... 6

Growth & Development...... 7

Major Insect Orders...... 7

Insect Behavior...... 10

Population Dynamics...... 11

Role in Forest Entomology...... 11

Population Processes...... 11

Population Models...... 11

Life Tables...... 14

Population Distribution...... 15

Insect Population Sampling Techniques ...... 15

Principles of Integrated Pest Management...... 16

Economic Injury Levels...... 16

Available tactics of Forest Pest Control...... 16

Integrated Pest Management...... 17

Root Insects...... 18

Introduction...... 18

Impact on Stand...... 18

Management...... 19

Conifer Root Weevils...... 19

Bark beetles, White grubs, Invasive weevils, Lepidoptera, Homoptera21

Stem Colonizing Bark Beetles...... 22

Introduction...... 22

Biology...... 22

Major Species...... 22

Management of Bark Beetles...... 24

Wood Borers...... 26

Introduction...... 26

Native Species...... 26

Metallic Borers, Long-horned Beetles ...... ……...... 26

Horntails, Lepidoptera...... 27

Ambrosia Beetles...... 28

Invasive Species...... 29

Emerald Ash Borer ...... 29

Asian Longhorned Beetle...... 29

Pine Sawyer / pine wilt nematode ...... 29

Horntail: Sirex noctilio...... 30
Tree Response to Defoliation...... 31

Introduction...... 31

Physiology of Defoliation...... 31

Relation of Control Options to Life History of Defoliating Insects ....32

Hardwood Defoliators...... 33

Lepidoptera...... 33

Coleoptera...... 36

Diptera...... 36

Orthoptera and Phasmodea...... 36

Thysanoptera...... 37

Diptera, Hymenoptera...... 37

Conifer Defoliators...... 38

Budworms...... 38

Tussock Moths...... 39

Caseworms and Bagworms...... 40

Conifer Sawflies...... 40

Regionally important defoliators…...... 41

Fluid Feeding Insects...... 42

Introduction...... 42

Homoptera...... 42

Mites: Acarina...... 44

Other...... 44

Shoot and Tip Insects...... 45

Introduction...... 45

Weevils...... 45

Shoot Moths...... 46

Bark Beetles...... 47

Cone and Seed Insects...... 48

Cone Moths...... 48

Seed Moths...... 48

Cone Beetles...... 48

Gall Insects...... 49

Appendix 1: Insect Population Sampling Techniques

Appendix 2: Major Categories of Insecticides; Mechanisms of Insecticide Resistance

ROLE OF INSECTS IN FOREST ECOSYSTEMS

I.Herbivory (=Phytophagy)

A.Host Range: Mono-, oligo-, poly- phagous

Implications to pest management

B.Plant parts (highly specialized)

Microsite

C.Impact

1. Can range from marginally beneficial to lethal

2. Implications to Management:

Stand level losses in forests

Individual losses in ornamentals

3. Beneficial: Bio Control of weeds (Alder) & Fungi

4. Ecological: Affects competition between plants

Can influence succession, forest structure, gaps, fire

5. Vector plant pathogens

Insect mouthparts

Sometimes mechanical, sometimes quite specialized

6. Must consider at multiple levels

Plant part:Tree may compensate: Diversion of energy, abscission

Stand level:Increase of light, moisture, release from competition

Release of bound biomass

II.Predation & Parasitism

A.Host range

B.Specialize on insect stages: Eggs, Larvae, Pupae, Adults

C.Sophisticated prey searching mechanisms

Odor - Plant wounds, insect

D.Management: BioControl

Ecology: Can enhance diversity of ecosystem; Not allow any one herbivore to reach high densities

III.Food For other Animals

A.Food webs

B.Antipredator mechanisms

Camouflage

Mimicry: Toxic insects, wasps, etc.

Chemical Defenses

Implications to Management: Sampling

Biological Control

IV.Saprophagy

Importance

Context of pest: Termites, Carpet beetles

V.Pollination

2/3 of flowering plants

Forestry - mostly hardwoods

VI.Pest Actions of Insects.

Only “pest” because they interfere with human objectives

Major pests include both introduced and native

INTRODUCTION TO ENTOMOLOGY

I.CLASSIFICATION AND DIVERSITY OF INSECTS

A.Arthropods

Phylum Arthropoda: Key Characteristics

ExoskeletonOpen circulatory system

Segmented body partsVentral nerve cord (decentralized)

Paired appendagesOpen respiratory system

Crustacea - Aquatic - 2 prs antennae - 2 body parts (cephalothorax, abdomen)

Millipedes - more than 1 pr/segm, scavengers

Centipedes - 1 pr/segm, predators

Arachnids - Spiders (pred), Ticks, Mites (Some are important pests) no antennae, 4 prs legs,

B.Insects

Class Insecta: Key Characteristics -

3 distinct body parts2 pr wings

3 prs legs1 pr antennae

Most diverse of all groups - 1 - 3 million species - @90% of all animals, over half of all life forms

C.Useful Field Guides to Forest Insects and Their Damage

Drooz: Eastern Forest Insects, USDA Misc. Publ. 1426, 1985

Furniss & Carolin: Western Forest Insects, USDA Misc. Publ. 1139, 1977

II.INSECT STRUCTURE AND FUNCTION

A.Exoskeleton

B.Major Body Regions

C.Nervous System

D.Circulatory System

E.Respiratory System

F.Digestive System

G.Reproductive System

III.GROWTH AND DEVELOPMENT

Types of Development
Hemimetabolous ‘Incomplete metamorphosis’
Holometabolous‘Complete metamorphosis’

Moulting

Endocrine control
Ecdysone
Juvenile Hormone

Life History Stages
Diapause
Dormancy:, Aestivation
Diurnal Rhytms
Migration

IV.MAJOR INSECT ORDERS

Introduction

Phylogenetic Order

28 orders; 8 orders contain >95% of species

Orthoptera (Grasshoppers);

Related orders include Phasmatodea (walking sticks) and Mantodea (mantids)

1.Chewing mouthparts

2.Incomplete metamorphosis

3.Leathery forewings, Membranous hindwings

Most not very important in forestry

Some important groups:

Walking sticks on oak in US; Eucalyptus in New Zealand

Grasshoppers on oak

B.Blattodea (formerly Isoptera) - termites

Chewing mouthparts
Incomplete metamorphosis
Highly social

Very common in forests; feed on cellulose (Indigestible - require protozoa and bacteria - basis of their social systems)

Beneficial - nutrient cycling

Damaging - wood products, sometimes trees

Blattodea - roaches

C.Thysanoptera - Thrips

1. Extremely small - Feathery wings

2. Highly modified mouthparts:

Intermediate between chewing & sucking

Piercing & sucking

Asymmetric

3. Intermediate metamorphosis

Several important species in forestry but not many

D.Hemiptera - Bugs

1. Sucking mouthparts

2. Incomplete metamorphosis

3. Suborders

a. Heteroptera

Some plant pests, many predators, some human pests

b. Homoptera - Aphids, Scale insects, Spittle bugs, cicadas

Plant feeders

Sometimes quite complex development

Important ectors of plant pathogens

E. Coleoptera

1. Largest insect order (@300,000): Most important pest group in forestry

2. Chewing mouthparts

3. Complete metamorphosis

4. Elytra (Thick & horny; Cover hindwings in flight)

Highly Diverse: Plant feeders, predators

Immatures - Grublike, Some free living

F.Diptera - flies – Fourth large orderest

1. Sucking mouthparts - adults

2. Complete metamorphosis

3. Adults - 2nd Pair of wings highly reduced "Haltere" – Stabilizing organs

4. Larvae - maggot like

Not major pest of forests

Important vectors of pathogens causing Human Disease

Parasitic flies - Tachinidae

Look like houseflies - hairy

Female attaches egg to larva (mostly Lep) or leaf

Predacious flies - Asilidae (Robber flies); Dolichopodidae

G.Lepidoptera

1. Third largest insect order: Second important pest group in forestry

2. Sucking mouthparts

3. Complete metamorphosis

4. Adults - Scaly wings

5. Less diversity than Beetles: Almost all are plant feeders as larvae.

Most feed on nectar as adults (some do not feed)

6. Larvae are damaging stage "caterpillars" - 3 pairs of true legs

4 - 5 pairs fleshy prolegs

7. Types of feeding

Defoliation, Mine leaves, stems, buds

H.Hymenoptera - Wasps, Bees, Ants, Sawflies, Woodwasps, Parasitic wasps

1. Second largest insect order; Most beneficial group in forestry

2. Chewing mouthparts - Modified

3. Complete metamorphosis

4. Adults - Membranous wings;

5. Ovipositor - Highly specialized - Defense, Insertion into plants or insects

6. Three Important Ecological Groups

a. Plant - feeders: Sawflies, woodwasps, galls: Pests

b. Parasites - Ichneumonidae & Braconidae: Benefit

c. Social Insects - bees, ants, wasps - pollination, predation:

7. Larvae

a. Caterpillar like (Sawflies > 5 prs prolegs)

b. Grublike

V.INSECT BEHAVIOR

A.Introduction: "Observable Physiology"

B.Feeding Behavior

1.Types of feeding

2.Host range

3.Specialization on plant parts

4.Host location

C.Reproductive Behavior

1.Mate location

2.Mating frequency

3.Oviposition

D.Orientation

POPULATION DYNAMICS

I.ROLE IN FOREST ENTOMOLOGY

A.Prediction

B.Management

Characteristics of Populations

II.POPULATION PROCESSES

A. Birth, Death, Immigration, Emigration

III.POPULATION MODELS

A.Exponential Growth

dn/dt = rN

Nt = N0ert

B. Sigmoid Growth

Carrying Capacity K

dn/dt = rN {(K-N)/K}

Nt= K/ (1+B-rt)

C.Competition

D. Predation

E.Density Independent and Density Dependent Factors

Density Independent Factors: The proportionate effect on population processes (Birth, death, reproduction, movement) is not related to population density.

1. Example: Early frosts in 1995, 1999, & 2007 caused high mortality to a budworm. But the proportionate mortality is not related to population density

Population

Yr.Before frostAfter frostMortality% Mortality

2002100050050050

2003800No frost

200450000No frost

200575000375003750050

2006100No frost

200720010010050

2. Example: Mortality and % mortality vary; Proportionate mortality related to precipitation, but not density.

Population

YearPrecipitationMay 1June 1Mortality% Mortality

20037500100 40080

2004420001000100050

200551500600 90060

200631000600 40040

2007625008001750 70

F. Density Dependent Factors: The proportionate effect on population processes (Birth, death, reproduction, movement) is related to population density.

1. Example:

Population rates and mortality due to disease are listed below. As the population increases, both the absolute mortality and the % mortality increase

Yr. / Population / Mortality / % Mortality
2002 / 1000 / 10 / 1
2003 / 5000 / 500 / 10
2004 / 100000 / 90000 / 90
2005 / 800 / 8 / 1
2006 / 10000 / 2000 / 20
2007 / 50000 / 25000 / 50

Types of density-dependent forces

Competition

a. Starvation

b. Can sometimes be have Non-lethal Effects:

Examples: Delayed Development, Reduced Fecundity

2.Predation and Parasitism: Both Numerical and Functional Responses

a. Numerical response: Predator population increases when prey abundant

b. Functional response: Consumption / predator increases when prey abundant

3. Disease

4.Density Dependence Can Sometimes be Positive

a. Allee Effects: Significance to invasive species

5. Some environmental effects can have a density-dependent component

C. Carrying Capacity, Sigmoid Growth and Equilibrium Behavior

Effect on Population and Per Capita Growth Rates
Time delays
Integrating Density-Dependent and Density Independent factors

D. Genetic Change

IV.LIFE TABLES

Life tables present the number of surviving individuals from an initial cohort, at a series of time intervals. They are used to predict future population densities, both between and within generations.

A. Age-Specific death rate: percentage that dies during a particular stage.

B. Cumulative death rate: percentage of original cohort that dies before a particular life stage is reached.

Example:

Stage / No. Surviving / Age - Specific
Death Rate / Cumulative
Death Rate
Egg / 1000 / 50% / --
Larva - 1 / 500 / 60% / 50%
- 2 / 200 / 50% / 80%
- 3 / 100 / 40% / 90%
- 4 / 60 / 58% / 94%
Pupa / 25 / 20% / 97.5%
Adult / 20 / -- / 98%

C.Key Factors

Source of Stage-specific mortality that best predicts year to year fluctuation

Not necessarily the highest mortality factor

How is it computed? a) calculate the age specific mortality rates; b) determine what factor is most responsible for mortality during each stage; c) determine which stage-specific mortality is most correlated with generation to generation change ; d) What is the agent that causes this mortality?

V.POPULATION DISTRIBUTION

Space

Random, Clustered, Even

B. Time

1. Seasonal abundance

Outbreak behavior

C. Space * Time Interactions

VI. INSECT SAMPLING

A. Sampling vs. Collecting

Absolute vs. Relative Methods
Appendix 1

PRINCIPLES OF INTEGRATED PEST MANAGEMENT

I.ECONOMIC INJURY

A.Relationship of Population Density to Yield Loss

B.Sampling

C.Decisions to Employ Control Measures

II.AVAILABLE TACTICS OF FOREST PEST CONTROL

A.Biological Control

1.Natural Components

2.Introduced Species

3.Enhancement of Native Control Agents

4.Biotic Insecticides

5.Advantages, Disadvantages

B.Silviculture

1.Species Composition and Planting Schedules

2.Thinning

3.Harvesting Schedules

4.Advantages, Disadvantages

C.Resistance Breeding

1.Genetic Variation

2.Operational Considerations

3.Biotechnology

4.Advantages, Disadvantages

D.Exclusion and Eradication

1.Quarantine

2.Relating Exclusion to Other Control Measures and Insect Biology

E.Chemical Control

1.Insecticides (Appendix 2)

a.Types

Advantages and Disadvantages
LD values
Systemic

2.Pheromones

3.Insect Growth Regulators

4.Antifeedants

III.INTEGRATED PEST MANAGEMENT

A.Optimum Combination

B.Applying General Principles To Specific Situations

ROOT INSECTS

I.INTRODUCTION

A.Increased importance

B.Taxonomy of major groups

C.General features of root insects

1.Slow development time

2.Oligophagous

3.Orientation to host odors

4.Clustered distributions

5.Low fecundity

6.Close symbiotic relationships with fungi

D.High Level of Niche Partitioning

1.Host age and condition

2.Microhabitat

3.Behavior

II.IMPACT ON STAND

A.Direct

1.Larval feeding

2.Adult feeding

B.Indirect

III.MANAGEMENT

A.Sampling

B.Control

1.Chemical

2.Biological

3.Silvicultural

4.Tree breeding

IV. CONIFER ROOT WEEVILS

A. INTRODUCTION

1.Types of Damage

2.Weevils: Curculionidae

a.Identification

b.Description

3.Relationships With Other Insects and Fungi

4.Increased Importance

B.MAJOR CONIFER ROOT WEEVILS:

1.Pine Root Collar Weevil: Hylobius radicis

a.Hosts

b.Distribution

c.Life cycle

d.Damage

e.Stand factors

f.Control and Management

2.Pine Root Tip Weevil: Hylobius rhizophagus (H. assimilis)

a.Hosts

b.Distribution

c.Life cycle

d.Damage

e.Control and management

3.Pales Weevil: Hylobius pales

a.Hosts

b.Distribution

c.Life cycle

d.Damage

e.Control and management

4.Pitch-eating Weevil: Pachylobiuspicivorus

5.Other Conifer Root Weevils

a.Warren's Collar Weevil

b.Strawberry Root Weevil

c.Eastern Pine Weevil: Pissodesnemorensis

d.Hylobiusabietis: Europe

V.BARK BEETLES (COLEOPTERA: SCOLYTIDAE)

A.Hylastes

1.Pests of western Douglas fir plantations, vectors of

Black Root Stain disease

B.Pseudohylesinus

VI.WHITE GRUBS (COLEOPTERA: SCARABAEIDAE)

A.Biology

B.Plantation Pests, Alternate Hosts

C.Control

VII. INVASIVE ROOT WEEVILS OF NORTHERN HARDWOOD FORESTS

A. General Biology and significance

B. Phyllobius oblongus

C. Polydrusus sericeus

D. Sciaphilus asperatus

VIII.LEPIDOPTERA

A.Conifer swift moth

IX.HOMOPTERA

A.Aphids

B.Cicadas

STEM COLONIZING BARK BEETLES

I.INTRODUCTION

A.Taxonomy: Coleoptera: Curculionidae: Scolytinae (formerly Scolytidae)

1.Bark beetles

2.Ambrosia beetles

B.Economic Importance

C.Distribution

D.Classification By Vigor of Hosts Selected

II.BIOLOGY

A.Life History

B.Host Resistance

C.Pheromones

1.Aggregation

2.Anti-aggregation

D.Microorganisms

1.Blue Stain Fungi: Ophiostoma, Ceratocystis

2.Digestion

E.Relationship of Life Stages to Control Tactics

F.Factors Predisposing Trees to Attack

III.MAJOR SPECIES

A.Mountain Pine Beetle: Dendroctonus ponderosae

Northwest and Rocky Mountains
Lodgepole Pine, Ponderosa Pine, Sugar Pine, White Pine
Grosmannia clavigerum formerly O. clavigera
Responses to climate change: Changes in voltinism, habitats, geographic range

B.Western Pine Beetle: Dendroctonus brevicomis

1.California and southwestern Rocky Mountains

2.Ponderosa pine

C.Southern Pine Beetle: Dendroctonus frontalis

1.Southern states

2.Loblolly, Virginia, Short Leaf Pine

3.O. minus; Basidiomycetes; Mites

D.Spruce beetle: Dendroctonus rufipennis

1.Alaska, British Col., Rocky Mtn states, North Central states, New England

2.White spruce, Sitka Spruce, Lutz spruce

3Variations in population behavior: Region; Population phase

E.Pine Engraver: Ips pini

1.Transcontinental

2.All pines, some spruces

3.Major Lake States bark beetle

4.O. ips

F.European Spruce Bark Beetle: Ips typographus

1.Europe

2. C. polonica

G.Turpentine Beetles: Attack Base of Weakened Trees; Vector Leptographium fungi

1.Red Turpentine Beetle: Dendroctonus valens

a.Transcontinental

b. Introduced into China in mid 1980’s.

2.Black Turpentine Beetle: Dendroctonus terebrans

a.Southern States

3. Dendroctonus murrayanae in western Canada, high elevations of US Rocky Mts

4. Dendroctonus micans in Europe

H.Other Conifer Bark Beetles - Moderately Aggressive. Capable of outbreaks under stress conditions

1.Southern States

a.Eastern 5 Spined Pine Engraver: Ips grandicollis

b.Small Southern Pine Engraver: Ips avulsus

2.Western States

a.Douglas Fir Beetle: Dendroctonus pseudotsugae

b.Fir Engraver: Scolytus ventralis

3.Eastern and Lake States

a.Eastern Larch Beetle: Dendroctonus simplex

I.Dutch Elm Disease

1.Imported Pest Complex

2.Smaller European elm bark beetle: Scolytus multistriatus, C. ulmi

Native elm bark beetle: Hylurgopinus rufipes

3.Biology of beetle, vectoring of fungus, and transmission across root grafts

4.Control

J.Other Bark Beetles Colonizing Angiosperms

1.Hickory Bark Beetle

IV.MANAGEMENT OF BARK BEETLES

A. Impacts

1. Forest Products

2. High Values Trees

a. Recreation, Watershed

b. Private

3. Wilderness

a. Old Growth

b. Endangered Species

c. Dispersal

B.Chemical

1.Insecticides

2.Pheromones

C.Biological

1.Natural Enemy Complex

a.Predators - Beetles, Flies, Mites, Woodpeckers

b.Parasites - Wasps, Flies, Nematodes

c.Disease Agents

2.Utilizing Biological Control

a.Problems

b.Role in Sanitation

D.Silviculture

1.Augmentation of Host Resistance

a.Thinning

b.Site Selection

c.Harvesting Schedule

2.Reduce Food Base

a.Age mosaic

b.Removal of large trees

c.Timing of operations

3.Population Removal

a.Removal of Infested Trees

b.Destruction of Slash

E.Survey Methods and Population Prediction

WOOD BORERS

I.INTRODUCTION

General Biology
Host Location
Ecological Role
Economic Impacts

Native Species

I."METALLIC BORERS," "FLAT-HEADED BORERS"

A.Coleoptera: Buprestidae

B.Life Cycle

1.Adult characteristics

2.Larval characteristics

3.Larval mines

C.Ornamental and Forest Pests

1.Bronze Birch Borer: Agrilus anxius

a.Resistant Varieties: Japanese White Birch--"Whitespire"

2.Two-lined Chestnut Borer Agrilus bilineatus

3.Control

D.Plantations

1.Poplar root girdler: Agrilus horni

2.Turpentine borer: Buprestis

E.Lumber Yards

1.Golden buprestid: Buprestis

II."LONG-HORNED BEETLES," "ROUND-HEADED BORERS"

A.Coleoptera: Cerambycidae

B.Life Cycle

1.Adult characteristics

2.Larval characteristics

3.Larval mines

C.Host relationships

1.Living trees

a.Sugar Maple Borer

b.Red Oak Borer

c.Locust Borer

d.Poplar Borers:

1.Saperda spp: association with Hypoxylon cankers

e.Management

2.Recently felled trees

3.Old moist wood

4.Dry seasoned wood

5.Twig and stem girdlers

III."HORNTAILS"

A.Hymenoptera: Siricidae

1.Description

2.Life Cycle

3.Control

V.LEPIDOPTERA: Cossidae

Oak carpenterworm

VI. AMBROSIA BEETLES

A. Coleoptera: Scolytidae (and related families)

Biology
Economic impact
Trypodendron

B. Management

1.Cutting Operations

Removal of brood trees and logs
Rapid removal of felled trees

2.Storage

Distance from sources of beetles
Maintain minimum inventories
Water Misting
Pheromones

VI. Termites

VII. Other

A.Carpenter Ants: Formicidae

Coleoptera: Bostrichidae, Curculionidae
Diptera: Agromyzidae

Invasive Species

A. Emerald ash Borer

Host range, Biology
Geographic range
Means of spread
Control

B.Asian Long-Horned Beetle

1.Introduced into NY in 1996; Chicago 1998.

2.Native range: China, Japan, Korea

3.Hosts

a Primary: Maple, poplar, willow

b. Other: Birch, elm, horsechestnut

4.Life history

a. @ 30 eggs/female; hatch in 10 days

b. Camrial Region: L1-L3; Sapwood: L4-L5.

c. Pupate in tree

Control: Sanitation, chemical

C.Pine Sawyer--Vector of Pine Wood Nematode

1.Japan, Portugal

a.Causal agents

1.Native beetle: Monochamus

2.North American nematode: Bursaphelencus

b.Host--Japanese red pine

2.Biology

3.Impact on host: Death of ray and axial paranchyma cells surrounding duct

epithelium, wilt

4.Control

a.Insecticides

b.Sanitation

c. Introduced entomophagous nematode

D.Sirex noctilio in Australia, New Zealand, S. Africa

1.Introduced Insect/Fungal Complex, Introduced Tree

a.Amylastereum spp & Stereum spp

b.Pinus radiata (Monterey Pine)

2.Life Cycle

a.Adults attracted to stressed trees (Monoterpenes)

b.Insert egg in first drill

Insert fungal arthrospores & mucus in second drill

c.Host responds by accumulating resins & polyphenols

d.Fungi & mucus impede host response

e.Multiple attacks

3.Wilt Symptoms & Tree Death

4.Control

a.Biological

1.Nematode: Deladenus spp

b.Sanitation

Resistance Breeding

5. Introduction and Establishment in US

E. Other

Poplar & Willow borer: Cryptorhynchus-hybrid poplars
Formosan Termite

TREE RESPONSE TO DEFOLIATION

I.INTRODUCTION

A.Types of Yield Loss

1.Direct

a.Mortality

b.Radial increment loss

c.Altered physiological allocation

2.Indirect