WHY DOES THIS HAPPEN
White flying things may appear around your plant as a result of an infestation of Whiteflies. These are small, moth-like insects that are closely related to aphids.
They can come in from outside, or they may be introduced to your plant collection via a new plant - this is why it's a good idea to quarantine new plants when your first get them to make sure they definitely don't have any pests on them. This will help prevent the spread of pests from plant to plant.
Whiteflies prefer warm conditions and are commonly found in greenhouses. They feed on plant sap, meaning they can be drawn to any type of plant. This feeding process tends to leave the plant weakened, so it's a good idea to try and eradicate an infestation before it worsens.
SYMPTOMS OF WHITEFLIES
The first symptom you'll probably notice is the flies themselves. They usually stick close to their host plant and will become active in the daytime flying around the plant - this can get quite annoying!
Other signs you can look out for are:
Clusters of white-colored insects, often with triangular wings, typically found on the undersides of the leaves
Concentric circles of pale yellow to brown ovals - these are the eggs of the Whitefly
The leaves of your plant may start to turn yellow
Premature leaf drop
General weakening of your plant / worsening of its health (Whiteflies interfere with its ability to photosynthesize efficiently)
A sticky residue on the leaves known as honeydew - this is a byproduct of the way that Whiteflies feed