Whiteflies are not real flies but small leaf sucking insects that are in adult stage covered with a white waxy material. Whiteflies belong to the group of true bugs, like aphids, mealybugs and scale insects. In particular in greenhouse cultures they may cause serious problems.
Adult whiteflies are around 2-3 mm in size; they do have wings and are able to fly. The younger stages are settled on a fixed place, mosty on underside of leaves. Only as very young individuals they have legs and are able to walk. As soon as they have moulted for the first time they loose their legs and will stay at the same spot for the rest of their lives. Larvae are oval shaped and translucent white - yellow in colour.
Especially the larvae are intensively sucking from plant leaves; they excrete the surplus of sugars that they consume as droplets of honeydew. This causes the typical 'shiny' appearance of infested plants. Sooty mould may start growing in the honeydew turning the plant leaves black. Photosynthesis is hampered. Some whitefly species may transfer viruses causing plant diseases. Infestation may be very serious; touching of infested plants causing a swarm of whiteflies.
- adults often on underside of young leaves in top of the plant
- eggs layed at underside of leaves
- larvae on underside of leaves, somewhat below the top of the plant
- stunted growth
- malformation of growing tip
- stunted leaves