The Content Of The Article:
- What are scale lice?
- Recognize a louse infestation
- These damages are caused by scale insects
- To prevent a louse attack
- Biological control of scale insects
Scale lice are plant pests that are very common in orchids - and should be fought quickly before they cause lasting damage to the plants. Because scale lice suck with the help of a Stechrüssels their food - the plant sap - from the Orchidee. Good camouflage and a high rate of reproduction can cause rapid spread on the affected plants. Then you should act.
What are scale lice?
Scale lice or Coccoidea are a superfamily of insects and belong to the plant lice (Sternorrhyncha). More than 3000 species are known worldwide, of which about 90 live in Central Europe. The small animals can grow between 0.8 and 6 millimeters. They suck and damage mainly on veins of hard-leaved orchid species such as Phalaenopsis, Cattleya or Vanda.
A lenticular body is characteristic of scale insects: the head and legs of the pest are so small that they are actually not recognizable. Female species are covered with a flat, bumpy shield. If the sign can be lifted, it is a so-called lid shield louse; If the sign sits firmly on, the animals are called Napfschildläuse. Napfschildläuse are much higher curved than Deckelschildläuse. Under the shield, which also serves as protection, the female animals lay a large number of eggs. After hatching, the offspring go through several larval stages. In the first stage, the small animals are mobile and thus can easily get from plant to plant. However, mature females are unable to move due to their protective shield attached to their backs. They are several months old. In contrast, male scale insects are usually winged and able to move - but only have a lifespan of a few days.
The life cycle of the scale insects: The female Schildlaus lays down to 250 moving larvae, which can distribute themselves then on the whole plant
Recognize a louse infestation
Because scale insects rely on good camouflage, they are predominantly on the undersides of orchids, where they are color-matched to their environment. The plant lice stay there and feed on the plant sap of the host plant with the help of their suction pipe. Under favorable conditions, more females than males are produced. However, if poor living conditions prevail, the composition of the population may vary accordingly: Scale insects are thus able to change their whereabouts.
Like most plant lice, scale insects are also among the pests that can multiply rapidly. Propagation occurs either sexually, also through tweeting, or by the so-called virgin production - a unisexual reproduction, in which the descendants arise from unfertilised egg cells.
These damages are caused by scale insects
Since scale insects are well camouflaged by their small size and inconspicuous color, the pests usually make themselves felt late. Affected plants, however, appear weakened after some time: The leaves deform and begin to wither, and there may also be changes in the flower shape. In most cases, scale insects are found near the roots, between the bracts and hidden areas on the underside of the leaves. The primary damage caused by the pests due to their suction activities on the orchids: As a food source they need the protein contained in the sap. However, since the plant juice consists largely of sugar, the animals excrete the substance that is superfluous to them as sticky honeydew. So that the scale insects do not stick themselves during this process, they hurl the dew away from themselves. This can lead to resinous deposits in the environment of the orchid - for example, on the windowpane or on the floor.
The suction activities on the plant also cause small holes. The wounds are ideal entry ports for harmful fungi and viruses such as the mosaic virus. Such diseases can lead to the death of the orchid.
The small scale insects are difficult to recognize on the leaves and are mainly found on the underside of the leaves
To prevent a louse attack
The pests are often brought into the house by newly purchased orchids. Therefore, you should take a closer look at all new acquisitions. If dead or live scale insects are present on the orchids or on neighboring plants, you should avoid these plants and refrain from acquiring them. Particularly endangered for an infestation with scale insects are stressed and weakened plants. Make sure you take care of your orchids. In healthy condition, they are less susceptible to diseases and pests.
The sooner the scale insects are discovered on orchids, the better the chances of getting rid of the plant lice. Regular checks on your plants can prevent infestation.
Biological control of scale insects
Once there are scale insects on one of your orchids, you should start fighting immediately. Otherwise, the affected plant will most likely infect neighboring plants and then self-induce. In order to avoid spread to other plants, the first measure should be the isolation of the diseased orchid. Once this is done, it is easiest to scrape off the scale insects with the help of a knife from the affected areas of the plant or to collect them by hand. However, this variant is not always expedient, as the young animals under the protective shield of the mother could be released. This has the consequence that the opposite of the desired effect occurs: The scale insects continue to spread.
Since the little animals like to hide between the bracts of the orchids, they should be removed. Thus, the pests have fewer opportunities to spread unnoticed on the plant - otherwise, more and more new populations can develop. The biological control measure is the use of tea tree oil. The oil is ideally spotted with a cotton swab on the affected parts of the plant. The tea tree oil removes the breath from the scale insects and they die. Caution should be exercised: Repeated use may cause such preparations to shed leaves on the sensitive plants.
A sprayed mixture of one liter of water, two tablespoons of olive oil and a few splashes of detergent has also proven itself in the fight against scale insects on orchids: The emulsion is applied with a spray bottle on the orchid. Hard-to-reach leaf axils are best treated with a brush. Since scale insects are very persistent, you also have to stand firm in the fight: Repeat the procedure best every fortnight. Another option for controlling plant lice is a mixture of one liter of warm water and fifteen grams of soft soap and 10 milliliters of methylated spirits. However, many soft and thin-leaved orchids are sensitive to such an aggressive solution. This variant should therefore never be injected, but only with a brush on the shoots apply. If you want to make sure beforehand if the affected orchid tolerates the solution, the effect on individual leaves can be tested.
Also, a fern herb broth of 100 grams of fresh or 10 grams of dried bracken helps against scale insects on orchids. The fern is put in water for one day. Boil the resulting broth and pass the juice after cooling through a fine-pored sieve. The liquid is sprayed twice a week on the affected areas. The fern herb broth acts both preventively and concomitantly with an infestation with scale insects. In case of a serious infestation, however, it is not sufficient as the sole countermeasure.
If you do not want to make a preparation yourself, you can also use ready-made concoctions such as "Promanal" from Neudorff or Celaflor "Sprouting Sprays White Oil." If all countermeasures are unsuccessful, you should part with the affected orchid, otherwise the sick plant will become one too much danger for their healthy plants.