Skip to Main navigation Skip to Left navigation Skip to Main content Skip to Footer

University of Minnesota Extension
www.extension.umn.edu
612-624-1222

Extension > Garden > Insects > Scale insects on Minnesota trees and shrubs > Scale insects that feed on conifers: Soft Scales

Print Icon Email Icon Share Icon

Scale insects that feed on conifers: Soft Scales

Edward H. Holsten, USDA Forest Service, Bugwood.org

Figure 11. Spruce bud scale on a Norway spruce.

Small Spruce Bud Scale

Physokermes hemicryphus

Appearance: Globular, reddish-brown, adult females are found at the base of new growth, often in clusters of three to eight individuals. They closely resemble the buds of their host tree (Figure 11).

Hosts: Spruce, particularly Norway spruce.

Damage: Lower branches are most commonly infested and heavy infestations can kill lower branches, reduce tree vigor and retard tree growth. Large amounts of honeydew are produced along with black sooty mold.

Life history: Overwinter as nymphs on undersides of needles. Females move to twigs in April and complete development. Crawlers appear in mid-June and settle on new growth to begin feeding. There is one generation per year.

Management: Late fall and early spring applications of horticultural oils will smother overwintering nymphs. Scales can also be effectively managed by a systemic treatment of dinotefuran applied in the spring. Insecticidal soaps, horticultural oils, insect growth regulators (pyriproxifen and buprofezin [available only to licensed applicators]), and residual insecticides (such as pyrethroids, acephate, and carbaryl) can be applied to treat the crawler stage. Timing of these applications when the crawlers are active is crucial for effective control.

United States National Collection of Scale Insects Photographs Archive, Bugwood.org

Figure 12. Fletcher scale on a yew.

Fletcher Scale

Parthenolecanium fletcheri

Appearance: Round, brown scales on twigs, at the base of the needles (Figure 12).

Hosts: Yew, arborvitae, and juniper.

Damage: Weakens plants, causing foliage to drop. Copious amounts of honeydew result in noticeable black sooty mold growth. It is a serious pest of yew.

Life history: Overwinter as nymphs on branches. They grow quickly in spring, producing noticeable damage and honeydew. Mature females lay eggs in May that hatch in mid-late June. Newly hatched crawlers look for feeding and overwintering sites. Crawlers do not move far and the density of scales can be higher on certain areas of infested plants. There is one generation per year.

Management: Late fall and early spring applications of horticultural oils will smother overwintering nymphs. Scales can also be effectively managed by a systemic treatment of imidacloprid applied in the fall or by spring treatments with dinotefuran. Insecticidal soaps, horticultural oils, insect growth regulators (pyriproxifen and buprofezin [available only to licensed applicators]), and residual insecticides (such as pyrethroids, acephate, and carbaryl) can be applied to treat the crawler stage. Timing of these applications when the crawlers are active is crucial for effective control.

Linda Treeful, Consulting Landscape Management

Figure 13. Pine tortoise scale on an Austrian pine.

Pine Tortoise Scale

Toumeyella parvicornis

Appearance: Adult females are reddish-brown, wrinkled, helmet-shaped, and occur in clusters on twigs (Figure 13).

Hosts: Scots, jack, red, Austrian and other pines.

Damage: Feeding causes needles to become off-colored and stunted, with trees taking on an overall pale, thin appearance. Annual, heavy infestations can kill branches or entire trees. The copious amounts of honeydew produced can attract large numbers of wasps, and often result in trees turning black due to the associated sooty mold growth.

Life history: Overwinter as fertilized females on branches. Females greatly enlarge by late spring and lay eggs. The tiny crawlers appear in late June to early July, and begin feeding on needles. Nymphs mature and mate. Females then seek overwintering sites on twigs and branches. There is one generation per year.

Management: Late fall and early spring applications of horticultural oils will smother overwintering nymphs. Scales can also be effectively managed by a systemic treatment of dinotefuran applied in the spring. Insecticidal soaps, horticultural oils, insect growth regulators (pyriproxifen and buprofezin [available only to licensed applicators]), and residual insecticides (such as pyrethroids, acephate, and carbaryl) can be applied to treat the crawler stage. Timing of these applications when the crawlers are active is crucial for effective control. Systemic insecticides are also effective.


« Previous: Armored scale insects feed on conifers | Scale home | Next: Armored scales insects feed on deciduous trees»

  • © Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy