Mealybugs

Mealybugs are typically a problem for indoor plants as well as in heated greenhouses. These tiny armoured insects feed on many types of indoor plants by piercing plant tissues and sucking on the juices. While they're at it, they often produce a sticky, honey-like substance on plant leaves. This can lead to a fungus called sooty mould, which makes the sticky areas blacken, a sign that mealybugs are present. There are many species of mealybugs and they thrive in warm environments.  

Mealybugs are covered with a whitish, mealy or cottony wax. This waxy protective skin protects against insecticides.  They usually find their way into your house by hitchhiking on other plants brought into the home.
 
Control:

• Quarantine new plants brought into the home for several weeks and observe for signs of mealybugs
• Dislodge them with a strong spray of water – repeat often as there can be multiple generations on one plant
• Washing in tepid water will remove sooty mould if it is present
• Use tweezers to physically remove the insects
• Prune off badly infested leaves or branches
• Discard badly infested plants
• Avoid giving plants too much nitrogen which puts on tender growth favourable to mealybugs

 
Source:

http://ipm.ucanr.edu/PMG/PESTNOTES/pn74174.html