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Small sap sucking juniper scale insects can encrust junipers (Juniperus species) and some other conifers such as cypresses (Cupressus and Chamaecyparis), Leyland cypress (x Cuprocyparis leylandii) and Thuya.
Juniper scale on juniper
Juniper scale is one of several species of scale insect encountered by gardeners. Juniper scale females are apparent on foliage as flat, round white scales, with a pale yellow centre up to 1.5mm in diameter. The males are narrower and reach 1 mm in length. It feeds on plant sap of junipers and some other conifers. The eggs of this scale insect hatch in June.
Juniper scale is often present on the foliage of susceptible conifers but only a problem if a heavy infestation develops when there may be yellowing and die back of the foliage. Unlike many other scale insects this species does not produce honeydew.
There can be other reasons for brown patches in conifers including insects such as the cypress aphid.
Juniper scale can be difficult to control, replacing severely infested plants can be considered. Only small trees can be treated and on large conifers treatment can be impossible.
Well-tended healthy plants are usually able to tolerate infestations and do not need treatment.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Brown patches in conifers
Chemical labels explained
Chemicals: using a sprayer
Chemicals: using safely and effectively
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RHS statement on pesticides in horticulture
Scurfy rose scale
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