OBJECTIVES OF INSECT DEFOLIATORS At the end of this section students should be able to: 1) Know the difference among polyphagous, oligophagous and monophagous.

OBJECTIVES OF INSECT DEFOLIATORSAt the end of this section students should be able to:

1) Know the difference among polyphagous, oligophagous and monophagous defoliators.

2) Know the principles of detection, evaluation and management of defoliators.

3) Know the life history, economic importance and ecological impact of the following defoliating insects:

(A) spruce budworm (B) gypsy moth (C) Douglas-fir tussock moth(D) Defoliators of the Southeastern U.S.

Defoliation damage by insects caneasily be recognized from symptoms:

•Foliage thin or absent•Frass “raining” from trees•Sometimes webs are apparent•Larva crawling up/down tree

Fall Webworm – Hyphantria cunea

SymptomsLeaf chewers – eat entire leaf and include thePine sawflies, Gypsy moths, Spruce bud worm

SymptomsLeaf skeletonizers – eat soft parts or theepidermal layers – not the veins.

SymptomsLeaf miners – bore inside leaves, betweenThe upper and lower epidermis. Includes, the Pine needle miners and the Aspen leaf miner

Blotch mines

Damage by defoliators

Primary Damage – Trees are killed by defoliation or growth is reduced.

•Conifers – 1 severe defoliationcan kill tree•Deciduous trees – better able to stand defoliation

Damage by defoliators

Secondary damage occurs when defoliated trees are weakened andsubject to attack by secondary pests such as wood borers, bark beetles, orsoil fungi – Armillaria spp

Defoliators – Taxonomic Groups

Lepidoptera: Many insect speciesIncludes Pine Butterfly, spruce budwormGypsy moth, catalpa worms

Defoliators

Hymenoptera-Sawflies

Red HeadedPine Sawfly

Loblolly pineSawfly

Oak slug sawfly

Defoliators –

Coleoptera: Cottonwood Leaf beetle, June beetles,Elm leaf beetle, & the Locust leaf miner.

Generalized Host Range of defoliators

Polyphagous - Many hosts, e.g.Gypsy Moth

Oligophagous – Few Hosts, e.g.Spruce budworm

Monophagous – one hosts, e.g. Larch casebearer

Population Dynamics:

Sporadic -

Periodic -

Spruce Budworm - Choristoneura fumiferana

Life Cycle

Spruce Budworm Larva

Adult Moth

Spruce Budwormegg mass on needle

Spruce budworm 3rd Instar in bud

Instars 4-6 feed on new foliage first and move to older foliage if necessary.

Populations are cyclic with peaks roughly every 8-10 yr. Major outbreaks every 60 years or so that corresponds with maturation of Balsam fir stand.

Management Considerations:

Stand Composition-

Chemicals-

Biologicals-

Budworm Treated area to left of road

End of SpruceBudworm Section