Ficus species are tender perennials that are often grown indoors for their decorative appeal and ability to grow in relatively low light. The warm temperatures and lack of natural predators indoors are favorable conditions for whiteflies that prey on ficus trees. In sub-tropical areas of southern states, ficus are grown outside. In these conditions, too, the warm weather and overuse of insecticides that kill off predatory insects leave the door open for whitefly infestations.
Many varieties of whitefly infest ficus species, whether indoors or outdoors. In Florida, a particularly severe infestation of the fig whitefly (Singhiella simplex) exploded in 2007, infesting many species of ficus and citrus outdoors. Ficus kept indoors may become infested with whitefly from the grower or have whitefly transmitted from nearby plants.
Whiteflies suck the moisture out of the leaves of any plant they infest, and their honeydew grows black mold that interferes with photosynthesis. When ficus are subject to whitefly attack, their leaves will yellow and then drop off, defoliating the plant in a matter of days or weeks. When the plant is disturbed, clouds of white gnat-looking insects will emerge from the branches.
If ficus are grown outdoors, it is a good idea to encourage the health of whitefly's natural predators. Avoid the frequent use of insecticides, as they will kill lady beetles, spiders and lacewing bugs. All of these bugs prey on whiteflies. For ficus grown indoors, inspect not only your ficus plant but any other plants you bring indoors for whitefly eggs and larvae. Isolate infested plants and treat them.
Biological and Mechanical Controls
Releasing predatory species such as ladybugs and lady beetles at the base of an infested ficus may help decrease the whitefly population as long as the habitat is hospitable for them. Make sure the ground has been watered and that they are sheltered when you first release them. Planting herbs that attract other predatory insects will help increase pressure on whitefly populations. For indoor ficus, vacuum the flying adults out of the air in the early morning when the air is cool and they move slowly. Freeze the bag full of insects for 24 hours to kill them. Hang whitefly sticky-tape traps from the ceiling and lower branches of your ficus.
According to the University of Missouri Extension, "insecticides commonly used for whitefly control include neem oil, insecticidal soap, horticultural oil, pyrethrins, permethrin, imidacloprid and malathion." Care should be taken to make sure that upper and lower leaf surfaces are coated and that pesticides are reapplied on schedule to make sure whitefly populations don't explode again. If insecticides are used outdoors, many of the predators of whitefly will also be killed, leaving the ficus vulnerable to another infestation.