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. 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 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 3 rd 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