At our request, Michelle Leonard-Mularz, Environmental Horticulture Agent at the UF/IFAS Extension Service, Monroe County has provided the details on how to properly control Whitefly. Note that sprayed insecticide will also kill beneficial insects and Michelle suggests alternative approaches below:
There is a parasitic wasp and a predatory beetle that feed on this whitefly and have been in all of the samples I have collected throughout the Keys. I just collected samples from Stock Island this week and both of these beneficial insects were feeding on the whitefly. These insects do an excellent job at parasitizing eggs of this whitefly and breaking the lifecycle. It is a good idea to reiterate this to your clientele when you discuss management of this pest. Anything that is sprayed and comes into contact with the whitefly will also kill the beneficial organisms that feed on this insect.
This whitefly will NOT kill their trees. It just takes time for the population of beneficial insects to reach populations to have adequate control. So no chemical control is necessary. If, however, the homeowner is adamant about using something for control, a systemic insecticide applied to the soil, will not harm the beneficial insects though it will take time for the material to be moved into the canopy. The products are listed on page 5 of the fact sheet. The label is the law! Always follow label directions and restrictions.
Remember, the waxy material and sooty mold will take time to wear off unless it is physically washed off.
View the “fact sheet” here.