The whitefly is one of the few insect diseases that can easily be seen with the naked eye. Whiteflies are between 1mm - 3mm in size and are mainly found on the top of plants, where the younger leaves are. If a large number of whiteflies are present on your plant, a small white cloud can be seen rising from your plant when shaken. This is one of the reasons why the whitefly is one of the most easily recognizable plant diseases.
Damage to the plant
The whitefly sticks into the leaves of the plant to extract its nutrients, which causes yellow leaves that eventually fall off. Whiteflies also have toxic saliva they use to attack plants. And they are often responsible for spreading other viruses. Besides this, the whitefly also leaves honeydew–a sticky substance where fungi can form and damage the plant. Whiteflies therefore, cause a lot of damage and must be controlled as quickly as possible.
Fighting whitefly is unfortunately very difficult. You can try spraying the whiteflies off your plant with a powerful jet of cold water (making sure to include the pupae and eggs at the bottom of the plant). But this will only work if the whitefly colony is still relatively small. If it is a larger colony, chemical control is the only option.
The whitefly occurs in places above 20 degrees, where humidity is not very high. A plant often becomes infected with whitefly if left outside for a long time during the summer. So pay extra attention when bringing your plants back inside after some time outdoors.
Because the whitefly spreads by flying, it is difficult to prevent. But occasionally spraying your plant with water can help, as the whitefly does not like wet surfaces.