Content may differ in form and is not being updated. Linnaeus, Taxonomic note Lepidosaphes ulmi was originally described in the genus Coccus. It has since been described as different species on different hosts, resulting in numerous synonyms. Biparental and parthenogenetic strains of L.
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Many hosts are commonly attacked by oystershell scale, making this one of the most destructive insect pests of trees and shrubs. Aspen, ash, cotoneaster, willow and lilac are among the most commonly damaged landscape plants. Oystershell scales are armored, light to dark brown, elongated and oyster-shaped. On some hosts the scale is covered with a fine powder of wax. Relatively few natural enemies appear associated with oystershell scale.
Parasitic wasps kill a few and a predatory mite has been observed to feed on overwintering eggs. Many scales and overwintering eggs die if areas of bark beneath them are killed. Vigorous plant growth, provided by proper siting and care, appears to help reduce scale infestations. Often only one or two trunks in an ornamental clump planting are seriously infested.
On smaller trees, old scale coverings and eggs can be destroyed by scrubbing the bark with a soft plastic pad. Very heavily infested branches may need to be pruned. The most effective chemical controls are "crawler sprays", applied to coincide with egg hatch. Carbaryl Sevin , chlorpyrifos Dursban , diazinon, Orthene, Tempo, Talstar, and Mavrik are currently available crawler sprays. Note: Aspen foliage is sensitive to liquid formulations of many insecticides.
Alternatively, insecticidal soaps or oil sprays applied in three to four day intervals during the crawler period can also provide control. Although most treatments are largely ineffective after scale crawlers have molted, summer foliar spray oils can control young nymphs for several weeks after they have settled on the bark.
Effectiveness of oils applied as dormant treatments has been more erratic with oystershell scale than with many other scales. This is because the eggs are well protected by the covering produced by the mother scale. Dormant applications of oils are more likely to be effective in spring, after the scale covering has weathered. Old scales remain in place for several years after the scales have died. In order to determine if controls are effective, old scales should be cleared from at least some of the branch, so that reinfestation can be detected.
Also, when crushed, dead scales are dry and flake easily off the bark; scales covering eggs typically will produce some moisture when crushed. The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana.
Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies.
State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. Toggle navigation. Discussion View source History. Oystershell Scale From Bugwoodwiki. Jump to: navigation , search. Scientific Name. Common Names. This page was last modified , 13 April by Bilal Bush. Based on work by Melissa and Allison Tiffany.
EPPO Global Database
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report. Abramovic T, Contribution to the study of scale insects on apple and peach trees in the Regional Territory of Belgrade. Interim report. Arhiv za Poljoprivredne Nauke, 41