Whiteflies are just as their name implies; they’re white and they sure do fly. They are very small but it is difficult to not notice them flying about. Looking at the underside of the leaves you may see the small hard shell-like larvae where they and the adults are sucking out sap. They leave a sticky honeydew and the leaves will turn yellow and wither.
Control: Isolate infected plant(s).
Begin treatment late in the evening as they are less likely to fly away. Have your vacuum on and ready, gently move the leaves and suck up the flies in the air when they’re disturbed. Very carefully carry your plant outdoors or to the shower so as not to disturb the remaining pests. Then, if outdoors, using a gentle spray from the hose, spray both sides of the leaves or if in indoors you can turn on the shower, making sure the water hits both sides of the leaves.
You can use a room temperature mild soapy water solution to spray or gently wipe the pests from the leaves; both the tops and undersides.
A systemic insecticide may be used if necessary. The roots absorb the insecticide and the insect will feed on it along with the sap. Always read instructions before use and be certain the product is appropriate for the plant and the insect you have.