Whiteflies pierce the underside of leaves and suck out the plant sap. Infestation leads to discolouration and wilting: leaves turn yellow, develop spots and die off. The excretion of honeydew causes the stomata to stick together, resulting in sooty mould (black fungal growth on the honeydew). The adult insects and their transparent larvae usually sit on the underside of the leaves and swarm when disturbed. Whiteflies are relatively rare on orchids, but soft-leaved species are usually infested when other host plants grow nearby.

There are approximately 1,500 species of whitefly worldwide, but only around 15 in Germany. The greenhouse whitefly was probably introduced from South America in 1848. The insects are only around 1.5 mm in size, with females usually slightly larger than males.

Reproduction occurs sexually with females and males. Fertilised, oval white eggs become females, unfertilised eggs become males, with a ratio of approximately 1:1. The females lay stalked eggs on the underside of leaves, followed by up to 4 larval stages (nymphs or crawlers). After 3-4 weeks, the fully developed, winged, white flies hatch. Temperatures around 20-25 °C and high humidity are ideal and drastically shorten the development time.

Chemical plant protection must be carried out consistently and repeatedly. In the event of infestation, at least 2-3 treatments at intervals of 2 weeks are necessary. It is advisable to spray wet plants in the evening so that the spray remains on the plant for a long time and can penetrate under the shields. Systemic agents are definitely preferable, but neem oil preparations can also have a positive effect. (Caution when using neem oil preparations on orchids)

Yellow sticky traps can indicate the onset of an infestation in good time, but are not sufficient for reliable control. Parasitic wasps, especially the Encarsia formosa wasp, are used as biological pest control. These parasitise the larvae (nymphs) of whiteflies and lay their eggs inside them. The larvae then turn black. New parasitic wasps later hatch from the black puparia, building up a parasitic wasp population.

Nothing specific about whitefly could be found in the available literature. However, as extremely toxic chemicals such as arsenic, nicotine and cyanide were always used, the animals had no chance of survival with any of these treatment methods.