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Arthropod Pests of Rhododendron

Stephen Bambara, Extension Entomologist

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

A number of arthropods attack rhododendron, but some pests such as aphids, whiteflies and scale that are problems in other parts of the country, are uncommon in North Carolina. Here are our most common pests. This information is just for quick reference. Consult the links for more complete information and control options.

Rhododendron & Azalea Lace Bug

- Adult with lacey wings, 1/8"
- Feed from underside of leaves
- Upper leaf surface white stippling to splotchy

- Underside leaf surface with black fly-speck-like fecal spots
- Adults and spiny nymphs on underside of leaf
- Overwinters as egg within leaf at leaf vein
- Egg hatch begins early Spring
. 2-3 generations

* Reduce stress of plant.
* Spray underside of leaves with malathion, orthene, pyrethroid or use imidacloprid systemic soil drench.

Southern Red Mite

- Discoloration noted during Summer or Winter
- Tiny chlorotic spots
- Flattened oval eggs or clear egg shells present in Summer and Winter with center thread
- Mites almost black body with pale yellow-brown legs
- All stages on underside of leaves
- Use 10X hand lens to check

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

Blueberry Stem Borer

- Dark-colored beetles 5/8 ". Long antennae, pale yellow with two black spots behind head.
- Lays eggs in new shoots below the bud. June -July.
- Larvae bore down core of twig where they overwinter.
- Two-year life cycle.
- Adults feed on undersides of leaves causing leaves to curl.
- Boring by larvae causes wilting and dieback of individual canes.
- Sawdust-like debris around small entrance holes in the bark.

* Prune and destroy wilting branches.
* If adults are seen in the previous year, spray the branches with permethrin.

damage from blueberry stem borer

Rhododendron Borer

- Leaves may brown
- Slender yellow-white larva found inside stem
- Infested twigs wilt and die or break off
- Adults emerge May-June; small black moth w/ white & yellow markings
- Eggs deposited on twigs
- Reddish frass evident in tunnel

*Prune out and destroy infested parts
*Protective bole and base sprays in spring with Astro or Onyx.
* Astro or Onyx foliar sprays in early spring for foliage feeding damage

Blackvine Weevil

- Larvae are legless grubs. Many herbaceous and woody hosts.
- Larvae feed on roots. Larger roots stripped or girdled.
- The adult weevils chew the edges of older leaves.
- Overwinter as mature larvae or pupae in soil. However, a few adults also survive the winter to feed and deposit eggs during a second season.
- Flightless adults, female need not mate.
- Adults live approximately 90 to 100 days.
- Adults feed at night and drop from the plant when disturbed.

* Imidacloprid soil/media drench.
* Scimitar + Demand; Talstar; Aloft. Three treatments.
* Timing with bloom important.
* Predatory nematodes helpful.
* Resistant varieties.

holes in leaf from blackvine weevil

Cranberry Rootworm

- Common on cranberry and rhododendron, w/ many other hosts.
- Adult, shiny brown/bronze. First appear about June.
- Larvae feed on roots and runners.
- Adults feed on leaves from underside, at night.
- Characteristic curved or "boomerang" shaped holes.

* Imidacloprid soil drench.
* Pyrethroid spray undersides of leaves.
* Beneficial nematodes in soil

holes in leaf from cranberry rootworm

Rhododendron Tip (or Gall) Midge

- Light brown midge, 1.25 mm long. Larva is whitish, flattened maggot 1.27 mm long.
- Uncommon in NC. Rhododendron only known host.
- Maggots feed exclusively on tender, new growth.
- Leaves inwardly-rolled with swollen, greenish-yellow tissue.
- Pale green bulges on leaves, stunted and distorted.
- Overwinter as pupae in the soil. The adult flies emerge and lay eggs in the spring as new plant growth develops.
- Damage late May or early June. May reappear on second flush of growth.
- Heavy infestations of this pest are unusual and sporadic.

* Remove and destroy newly infested foliage. This practice may eliminate an infestation within a single year or two.
* Imidacloprid, dinotefuran, or orthene as spray or soil drench effective if applied prior or very early.

midge larva
curled leaf

Azalea Caterpillar

- "U" posture when disturbed.
- Red head. Yellowish with black stripes. Stripes "broken" on older larvae.
- Generally feed in groups. Typically late summer/early fall.
- Occasional pest. One generation.

* Knock off or pick off and destroy.
* B.t. if small, pyrethroid, Sevin, or other.

azalea caterpillar

Climbing Cutworms

- Smooth-skinned noctuid caterpillars with various markings.
- Several species, many hosts.
- Climb shrubs at night to feed on buds and new growth.
- Pupate in soil; some species have multiple generations.
- Curl into a "C" when disturbed.
- Active late spring-summer, mild winter days.

* Acelepryn, pyrethroid, Sevin or some other contact insecticide should give adequate control of climbing cutworms.
* Disturbance of duff/mulch, and stem barrier may be helpful.

cutworm larva

( - ) = symptoms and diagnostic information
( * ) = management suggestions
Alternative plant suggestions- barberry, mahonia, pieris

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.


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. Photo credits: James R. Baker & S. Bambara. Cutworm -Lacy Hyche, bugwood.org. Permission required.
ENT/ort-154. July, 2010.
Web page last reviewed January, 2011.