OBJECTIVES OF INSECT DEFOLIATORS
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OBJECTIVES OF INSECT DEFOLIATORS At 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.

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  • OBJECTIVES OF INSECT DEFOLIATORS

  • At 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.

  • 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 can

  • easily 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


Symptoms

Leaf chewers – eat entire leaf and include the

Pine sawflies, Gypsy moths, Spruce bud worm


Symptoms

Leaf skeletonizers – eat soft parts or the

epidermal layers – not the veins.


Symptoms

Leaf miners – bore inside leaves, between

The upper and lower epidermis. Includes, the

Pine needle miners and the Aspen leaf miner



Damage by defoliators

  • Primary Damage –

  • Trees are killed by defoliation

  • or growth is reduced.

  • Conifers – 1 severe defoliation

  • can kill tree

  • Deciduous trees – better able

  • to stand defoliation


Damage by defoliators

Secondary damage occurs when

defoliated trees are weakened and

subject to attack by secondary pests

such as wood borers, bark beetles, or

soil fungi – Armillaria spp


Defoliators – Taxonomic Groups

Lepidoptera: Many insect species

Includes Pine Butterfly, spruce budworm

Gypsy moth, catalpa worms


Defoliators

Hymenoptera-

Sawflies

Red Headed

Pine Sawfly

Loblolly pine

Sawfly

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





Spruce Budworm

egg mass on needle


Spruce budworm 3rd Instar in bud



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: Major outbreaks every 60 years or so that corresponds with maturation of Balsam fir stand.

Stand Composition-

Chemicals-

Biologicals-


Budworm Treated area to left of road Major outbreaks every 60 years or so that corresponds with maturation of Balsam fir stand.


End of Spruce Major outbreaks every 60 years or so that corresponds with maturation of Balsam fir stand.

Budworm Section


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