Cottony Camellia Scale on Holly

The cottony camellia scale is most commonly reported on holly in Kentucky, but it is also found on other hosts, including yew, euonymous, maple, and hydrangea.

The cottony white egg sacs of this soft scale appear on undersides of leaves (Figure 1) in May and egg hatch (Figure 2) occurs during June.  Crawlers settle on undersides of leaves and begin to feed on leaves during June. During this time they are susceptible to insecticidal soap; however, several applications may be needed due to an extended egg hatch.

Figure 1. Cottony camellia scale on holly (Photo: Brenda Kennedy, UK)

Figure 1. Cottony camellia scale on holly (Photo: Brenda Kennedy, UK)

Figure 2. Eggs of cottony camellia scale just before hatching (Photo: Lee Townsend, UK

Figure 2. Eggs of cottony camellia scale just before hatching (Photo: Lee Townsend, UK

Managing Cottony Camellia Scale

Insecticides

Scale control is challenging and may require action over several seasons. Here are some points to consider:

  1. Proper timing of foliar sprays is a key to success. The spray must target newly hatched crawlers during June. Once settled on the plant, scale insects develop a protective covering that insecticides do not penetrate easily. The extended period of egg hatch may require two or more applications.
  1. Thorough spray coverage is essential. Depending on the type of insecticide used, control may be achieved by direct contact with the insects and/or picked up as they crawl over treated surfaces.

Many insecticides are labeled for control of scale infestations on trees and shrubs. Biorational choices include ultra-fine horticultural oils, insecticidal soap, and neem (azadirachtin). These insecticides will have minimal impact on beneficial species that help to regulate scale infestations, but they provide no residual protection. Conventional insecticides include those with one of the following active ingredients: bifenthrin, cyfluthrin, permethrin, or malathion. These products will provide residual control of active crawlers, but they have a significant impact on the lady beetles and tiny wasps that attack scales.

A dormant oil spray can be effective in controlling overwintering scales. Check the label for instructions and restrictions.

Reduce Stress

Scale infestations are often associated with stressed trees. Evaluate infested trees to identify and correct factors that may be contributing to stress. Prune heavily infested branches if practical.

 

By Lee Townsend, Extension Entomologist

 

Posted in Landscape Trees & Shrubs