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Arthropod Pests of Hemlock (Tsuga sp.)

Stephen Bambara, Extension Entomologist

CAUTION: This information was developed for North Carolina and may not apply to other areas.


- Green or brown cone-like bags 1/4" - 3"
- Defoliated areas of plants
- Infestation spreads slowly from one plant to adjacent plants

- Breakage points at callous branch swellings
- Caterpillars remain enclosed within protection of bag
- Overwinters as eggs within bags
- Eggs hatch May; larvae feed through July

*Hand pick bags any time of year
*B.t., Sevin, pyrethroid, Conserve June to midJuly

bagworm bag

Hemlock Woolly Adelgid

- Fluffy white "cotton" at base of needles
- branches to entire trees with brown needles
- branches to entire trees defoliated

*hort oil sprays
*imidacloprid soil drench or trunk injection
*dinotefuran (Safari) soil drench, or trunk spray
Concern of runoff and water contamination with some products.
Other management.

adelgids on twig

Hemlock Rust mite

- Microscopic
- Yellowing needles, premature drop, more common in spring
- Overwinter eggs on needles, adults on bark
- More common on high nitrogen fertilization

*Horticultural oil, Floramite, Hexygon, sprayed in cool season while mites active. Follow-up sprays often required with oil.
*Phytoseiid mites and other natural predators

hemlock twig

Elongate Hemlock Scale

- Armored scale, two generations
- Elongate in shape
- Found on undersides of needles
- Dieback may occur, often from bottom limbs upward
- Crawlers hatch late spring
- Overwinter as female on needles

* Horticultural oil during crawler stage repeat in 14 days
*Dinotefuran soil drench or trunk spray
*Discontinue nitrogen fertilization

scale infested underside

Indian Wax Scale

- White, waxy, cap-shaped cover
- Circular to oval with reddish insect inside
- Found on stems on boxwood
- Leaves may yellow and drop early
- Crawlers hatch spring
- Overwinter as eggs under scale

* Horticultural oil during crawler stage; repeat treatment 14 days later
*imidacloprid or dinotefuran soil drench for systemic management

indian wax scale

- Browning noted during Summer or Winter
- Browning located on inner portions of branches
- Flattened oval eggs or egg shells present in Summer and Winter with center thread
- Almost black body with pale yellow-brown legs
- Streak dark olive when smeared on paper
- Eggs laid at base of needle
- Use 10X hand lens to check

*Horticultural oil, Floramite, Hexygon, sprayed in cool season while mites active. Follow-up sprays often required with oil.

spruce spider mite on needle

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical.

For assistance, contact your county North Carolina Cooperative Extension Service agent.

Other Resources

Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Prepared by:S. B. Bambara, Extension Entomologist. Photos © J.R. Baker and S.Bambara (permission required), and Bugwood.org.
ENT/ort-150. December, 2009
Web page last reviewed January, 2011 by the webperson.