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Scale insects can be identificate as a small brown or green ball or spot. They are about 3 to 4 mm in size and are often found around the veins on the underside of leaves, as well as on the top of leaves. Scale insects often occur in colonies. Scale insects - like soft scales - are insects with hard shells. The only difference with soft scale is that the scale insect (unlike the soft scale) does not secrete honeydew. Also, the carapace of a scale aphid is detached from the body, whereas in a soft scale it is fixed. It is related to the aphid family, but unlike the aphid, scale insects have a shield that cannot be removed in this insect. 

Because scale insects are often found in hidden places in crops, their damage is not always clearly visible, which is why these insects are often not detected until a later stage. 

There are many different types of scale insects, each with different characteristics such as shape, color and size. They look like flat discs and are very small, up to a mm in size. Their bodies have a small (usually) brown or black scaly shield. The males of certain aphid species develop in a white, waxy cocoon. In practice, these species can sometimes be confused with mealybugs.

Controlling scale insects is not easy because there are very few insecticides available against this pest. In addition, existing application techniques are not well suited, because they often prevent access to where the scale insects are located. Therefore, natural predators are often used to fight scale insects. Read more about this below.

Parasitic wasps or predator beetles can be introduced as a biological approach to combat scale insect:

• The parasitic wasp; Encarsia citrina parasitizes various species of scale insect, such as Abgralaspis cyanophylli, Pinnaspis aspidistrae, Pseudalacaspis cockerelli, and Aspidiotus, Cryptolaemus, Disapis and Hemiberlesia species. Aphidoletes aphidimyza gall midges also target scale insect.
• The predatory beetles; Rhyzobius lophantae is a ladybug that eats all stages of the scale insects. Especially the larvae. 

Older scale insects often have a thick shield cover. This makes it difficult to fight it. Therefore, try to focus chemical control on the young scale insects without a shield; at this stage this insect is at its most vulnerable. When scale insects are detected in a greenhouse, it is therefore important to spray promptly so that the newly hatched insects are treated straight away. The older insects are often found low in the crops. Spray more liquid here to fight this pest properly. Please note that in many cases, different stages of development will occur together. Please ask your account manager which insecticide is available in your country.

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