Fight scale insects quickly and effectively: We will show you how to quickly get rid of the unwelcome lice using biological and chemical agents.
Like other plant lice, scale insects are equipped with a proboscis. With this they suck up the energy-rich plant sap and thus weaken the affected plant. For this reason, scale insects are among the pests and they are a big problem, especially on indoor plants. Successful control also requires a consistent approach to get rid of the annoying beasts. But did you also know that valuable raw materials are made from scale insects? In the past, certain species were primarily used to supply the red pigment carmine. In the past, this gave many lipsticks and foods a strong red colour. Even the red Campari was dyed with carmine some time ago.
Detect scale insects
The scale insect family (Coccoidea) is relatively species-rich. Around 100 species of plant suckers are represented in Central Europe. This diversity of species means that scale insects differ significantly from one another in some cases. In our opinion, it is therefore important to recognize the general signs of a scale insect infestation and not to get caught up in the visual details of the different scale insects. Trees and vines are also infested by scale insects, but for the hobby gardener it is usually infested indoor plants that are the real problem. The scale insects particularly like to look for orchids, palm trees, ficus, citrus trees and oleanders as host plants.
A heavy infestation usually occurs in winter and spring when the plants are weakened by poor site conditions. Then the scale insects, which are 0.8 to 6 mm in size, multiply extremely quickly and become a problem for the affected plant. They like to hide at the base of leaves, the underside of leaves and other hard-to-reach places on the plant, which makes finding them even more difficult. A sure sign of a scale insect infestation is honeydew. Just like aphids produce thefemale scale insects also eat the sugar-rich honeydew, which quickly sticks whole leaves together. In connection with the immobile scale insects and the characteristic dorsal shield, this is a sure sign of a scale insect infestation. The scale insects often appear in colonies, which is why many pustule-like structures concentrated in one part of the plant also indicate scale insects.
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Scale insects are very variable in their nature, depending on their stage of development and gender. In principle, we only see the older female scale insects as pests. In their later development, the females have a distinctive shield for protection. This protective shield is also necessary because the female louse is completely immobile from the second larval stage and thus cannot escape from predators. At this point, the females are busy taking in the plant sap through their proboscis, laying eggs and releasing honeydew. The females can also lay fertile eggs without the fertilization of a male. This so-called virgin birth is responsible for the rapid reproduction of scale insects.
The eggs of scale insects are often protected close to or directly under the mother. The 0.8 mm small young larvae hatch from them. These larvae are still mobile and can therefore look for a new place on the plant in order to use the plant sap there as food. From the second larval stage, the larvae lose their mobility again. The males of the scale insect, on the other hand, are always mobile and usually winged. Nevertheless, they have a deplorable fate: their only purpose is to fertilize the females. The males cannot take in any food because their intestines and mouthparts are severely reduced. For this reason the males only live for a few days.
Prevent scale insects
Since scale insects particularly like to infest houseplants such as orchids and palm trees, the houseplants should be checked regularly for the suspicious shields of the scale insects, especially in winter. However, often only the large female and immobile scale insects can be detected during the assessment. The young larvae, which are less than a millimeter in size, are almost impossible to find for the human eye. Nevertheless, a scrutinizing look at newly acquired houseplants cannot hurt, because scale insects are not so easy to fight.Because the male scale insects can fly, one might conclude that they are also responsible for the spread. Thats not right. The flight skills of the males are very limited and they cannot lay eggs and therefore cannot reproduce on their own.
In addition to the early detection of a scale insect population, the condition of the plant is crucial. Scale insects often multiply rampantly on their host plants because they are weakened by the location. The most common cause is the lack of light intensity in winter and also in spring. The lack of light in connection with dry and often too warm air is pure stress for most potted and indoor plants. Excessive nitrogen fertilization has an equally bad effect on the vitality of plants. These factors result in a very vulnerable plant that can hardly defend itself against a scale insect infestation. Remedy can only be created to a limited extent. For almost all potted plants, fertilization should be suspended in winter. If your indoor plants do not get enough light in winter, then the plants should also be kept as cool as possible. Only at cooler temperatures can the plant adapt its metabolism to the poor light conditions. In addition, the scale insect also develops more slowly at low temperatures.
Caution: Of course, the plant should only be kept as cold as it can tolerate itself!
Fight scale insects
Most of the time, an infestation with scale insects is only recognized when they have already multiplied quite well. At this point, collecting the scale insects usually no longer makes sense. In addition, animals can remain undiscovered in hidden places, just like the small young larvae. The scale insects would multiply rapidly again and the problem would not be eliminated.
Biological control of scale insects
Control of scale insects is possible with sustainable methods such as organic pesticides and beneficial insects. Oil preparations are usually organic pesticides and are effective against scale insects when used correctly. The oil forms a thin film around the lice and suffocates them. However, many plants react sensitively to wetting with oil and can be damaged. Before wetting the whole plant with the oil agent, the preparation should be applied to a small part of the leafbe tried out.
A good alternative is an organic pesticide that uses azadirachtin, i.e. the active ingredient from the seeds of the neem tree. Azadirachtin has a partial systemic effect, i.e. it is distributed in the leaf and catches sucking pests such as scale insects even if they have not been sprayed directly. Our Plantura organic pest-free neem can be used indoors on ornamental plants and even fresh herbs against scale insects.
Chemical control of scale insects
Controlling scale insects with non-biological means is actually a disproportionate risk that can be avoided. Beneficial and organic compounds are now powerful enough that the more harmful conventional agents don't have to find their way into your home.
However, agents based on paraffin oil or synthetic pyrethroids such as lambda-cyhalothrin are approved for use in the House and allotment approved. Ready mixes are available for spraying or pouring, as well as sticks that help distribute the active ingredient systemically through the plant's sap stream. Important: When using plant protection products, always follow the recommendations for use and ask the manufacturer before buying how, where, when and on which plant the product can be used.
Fight scale insects with beneficial insects
Because beneficial insects are highly specific and only attack individual scale insect species, beneficial insects cannot be used against all scale insects. Here, the identification of the exact scale insect species would be the basis for effective control. A beneficial insect that is effective against many scale insects is the parasitic wasp Metaphycus helvolus. It sucks off young and middle larval stages and also parasitizes the females by laying eggs inside their bodies.metaphycus helvoluscan be against the hemispherical cupschildlaus ( saissettia coffeae), the black cupschildlaus ( saissetia oleae) and the common scale insect (Coccus hesperidum) can be used. Important: beneficial insects are sensitive, highly specialized organisms. When using them, a special temperature range often has to be observed or the lighting and humidity have to be regulated. Therefore, before use, read how the beneficial insects can best do their job. The success of the control depends largely on the conditions.
Another species of plant lice thatmany gardeners struggle with is the aphid. Find out everything about the appearance, origin and different types of aphids in our profile.