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Small sap sucking hemispherical scale insects can encrust the leaves and stems of a wide range of glasshouse plants.
Hemispherical scale (Saissetia coffeae) on Climbing fern (Lygodium circinatum)
There are many types of scale insects encountered by gardeners, they are sap sucking true bugs. Hemispherical scale is a dark brown, round, convex scale insect up to 4mm in diameter. It is found on the leaves and stems of indoor and glasshouse plants such as ferns, cycad, ornamental asparagus, Stephanotis and many others. It produces honeydew and breeds throughout the year.
This scale insect rarely causes direct damage to plants. Apart from the presence of the insects the main symptom is the presence of honeydew on which sooty mould can grow.
It can appear similar to other diaspid scales.
Hemispherical scale insects can be difficult to control; replacing severely infested plants should be considered.
Well-tended healthy plants are able to tolerate infestations. Physically squashing or removing scales may control light infestations.
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Hemispherical scale feed by sucking sap from the leaves and stems of various glasshouse plants. Scales are named for the waxy shell-like casing which covers most of their body. When mature, the females lay their eggs under the protection of this shell.
All hemispherical scales are female and reproduction is continuous throughout the year and entirely parthenogenetic. The eggs hatch into small active nymphs, known as crawlers, which wander over the plant surface until they find a suitable place to feed. They then become immobile and begin to produce their characteristic scale covering.
Infestations of scale insects are spread by the crawler stage, which may travel quite long distances before stopping to feed, and which can be spread by wind currents.
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