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

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Scale insects that feed on conifers: Armored Scales

Jeffrey Hahn, University of Minnesota Extension

Figure 9. Austrian pine infested with pine needle scale.

Pine Needle Scale

Chionaspis pinifoliae

Appearance: White, oval-elongate scales, 1/8 inch (2.5-3 mm) long (Figure 9).

Hosts: Pine, spruce, fir, hemlock and Douglas fir

Damage: Light to moderate feeding causes a stippled or yellowing appearance to needles sometimes causing needles drop. Although not common, when heavy, persistent infestations occur, they can severely damage and reduce the vigor in trees.

Life history: Overwinter as eggs beneath the dead mother scale. Eggs hatch in mid-late May and the mobile crawlers seek feeding sites on new needles where they settle and form their scale shell. Eggs are laid in the fall. There is typically one generation per year in Minnesota. A closely related species (Chionaspis heterophyllae), much less common in Minnesota, may produce a second generation in August.

Management: Insecticidal soaps, horticultural oils, insect growth regulators (pyriproxyfen and buprofezin [available only to licensed applicators]), and residual insecticides (acephate, pyrethroids, carbaryl) are effective as spray treatments for the crawler stage of the scales. Timing of these applications to the crawler stage of the scale is crucial for effective control. Systemic management using dinotefuran as a soil application or as a bark treatment is effective when applied in the spring. Combining systemic treatment with a crawler spray will provide the most effective management.

Jeffrey Hahn, University of Minnesota Extension

Figure 10. Black pineleaf scale on Austrian pine.

Black Pineleaf Scale

Nuculaspis californica

Appearance: Black, oval-elongate with gray margins and a whitish or yellow round center, 1/12 -1/10 inch (1.5-2.0 mm) long (Figure 10).

Hosts: All pine species and Douglas fir

Damage: Light to moderate feeding cause needles to turn yellow and drop. Severe infestations can cause needle stunting and death in young trees and reduce the vigor of mature trees. This scale can be associated with stressed trees.

Life History: Black pineleaf scales overwinter as immature scales. Adults are present during late spring. Eggs hatch in mid-late July and the mobile crawlers seek feeding sites on new needles into August. They eventually turn into second instar nymphs where they remain until spring. There is one generation per year.

Management: Insecticidal soaps, horticultural oils, insect growth regulators (pyriproxyfen 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 management using dinotefuran as a soil application or as a bark treatment is effective when applied in the spring. Combining systemic treatment with a crawler spray will provide the most effective management.


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