cottony camellia scale on yew

Cottony camellia scale on yew. Photo: Dawn Dailey O'Brien, Cornell University, Bugwood.org

Updated: March 22, 2022

Key points

  • Cottony camellia scale (Pulvinaria floccifera), also called cottony taxus scale, is a non-native type of soft scale insect that can be difficult to manage as their waxy body covering shields them from predators and certain pesticides. Learn more about scale insect groups and biology on our Introduction to Scale Insects page.
  • Cottony camellia scale is a common pest of camellia, yew, holly, and several other trees and shrubs. Heavy infestations can cause leaf yellowing. The impacts of honeydew production and the resulting growth of sooty mold will range from being an aesthetic nuisance to suppressing plant growth.
  • Target monitoring and control efforts to the vulnerable crawler stage. Learn more about what to look for on our Monitoring for Scale page. 

Appearance

  • Mature female covers are oval, yellow-tan with a brown margin, and up to ⅛” (3 mm) in length. The cottony white ovisac (egg case) they produce behind their covers are about ¼” (6 mm) in length.
  • There are either no males or they are rarely seen.
  • Crawlers are pale yellow.

yellow-tan mature female covers of cottony camellia scale
Mature scale are well-camouflaged before the formation of the prominent white ovisacs.
Photo: United States National Collection of Scale Insects Photographs, USDA Agricultural Research Service, Bugwood.org
White ovisac produced by female
Females produce a white ovisac behind their bodies. Dead females fall off the plant, leaving their ovisacs attached to the leaf.
Photo: Brian Kunkel, University of Delaware, Bugwood.org

Common host plants

  • Dozens of species in over 37 plant families are used by this species. This is not an exhaustive list.
  • Evergreen shrubs, including camellia (Camellia), euonymus (Euonymus), holly (Ilex), yew (Taxus), and sweetbox (Sarcococca);
  • Deciduous flowering shrubs, including hydrangea (Hydrangea), and beautyberry (Callicarpa);
  • Trees, including mulberry (Morus) and maple (Acer).

Where to look

  • Mature females, most noticeable when producing egg sacs, will mainly be found on the undersides of foliage. Egg sacs remain attached to the foliage after the female dies and falls off the plant.
  • On deciduous plants, they will overwinter on bark. On evergreens, they can remain on the foliage.

Plant damage

sooty mold on sweet box
Sooty mold on sweetbox (Sarcococca spp.)
  • Moderate to heavy infestations will produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
  • Heavy or prolonged infestations can cause leaf yellowing and a decrease of the plant’s vigor. Dieback is not common.

Honeydew and Sooty Mold

 Life cycle

  • There is 1 generation per year in Maryland.
  • The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is from mid-June through mid-October.
  • They overwinter on the bark (for deciduous hosts) or foliage as juveniles. Females move back onto foliage when ready to lay eggs in spring.

Management

Refer to our general scale management recommendations for both chemical-based and pesticide-free options. When pesticides are warranted, a combination of dormant oil applications and the use of systemic or growth-regulating insecticides is the most effective approach. For large populations, scale suppression may require more than one year of intervention, and professional pesticide applicators will be needed to apply certain treatments. Mature trees should be evaluated by a certified arborist.

The long egg-laying and crawler emergence period means that monitoring and treatment may need to occur several times a year to be effective. If you do not wish to use pesticides and are not obtaining good control from manual removal efforts alone, remove and replace the infested plants.

Introduction to Scale Insects

Pesticide sprays should be avoided when red-spotted black lady beetles are present, as they are a scale predator.

Timing details for monitoring and pesticide use

Begin monitoring for crawlers right before the expected emergence period for each generation. Since weather trends can shift date ranges, a more reliable prediction of timing can be made using Growing Degree Days and Plant Phenological Indicators. Below are refined estimates of egg hatch and the beginning of crawler emergence:

  • 649 degree days
    • After the peak flowering of Yellowwood (Cladrastis lutea)
    • Before the peak flowering of Japanese Snowbell (Styrax japonicus)
white flowers of a yellowwood tree
Yellowwood blooms
Photo: Miri Talabac
blooms of a Japanese snowbell tree
Japanese Snowbell blooms
Photo: Miri Talabac

Adapted from: Davidson, J.A. and M.J. Raupp. 2014. Managing Insects and Mites on Woody Plants: an IPM approach. Third Edition, revised. Tree Care Industry Assoc. Londonderry, NH. 175pp. Illus. and the Pest Predictive Calendar, also the Scale Crawler Emergence Period chart compiled by Stanton Gill, Suzanne Klick, and Sarah Kenney.

Complied by Miri Talabac, HGIC Consultant. 2021