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:

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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


Blotch mines


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


Life Cycle


Spruce Budworm Larva


Adult Moth


Spruce Budworm

egg 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 Spruce

Budworm Section


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