Ficus or ornamental fig trees (as opposed to fruit-bearing figs) are a very popular indoor or outdoor ornamental plant in the United States. If kept in a pot, the tree will not grow too large; once placed in the ground, some species (such as the Benjamina) can grow very large, and their shallow roots have a habit of buckling sidewalks and creating large bumps in asphalt and pavement. While ficus trees are one of the hardier ornamentals in warm climates, even they succumb to occasional insect infestations.
Cuban Laurel Thrip
One of the most common infestations with ficus trees, particularly outdoor trees, is that of the thrip. While feeding, adult thrips leave sunken dark spots along the spine of young, tender leaves. As young thrips feed on these leaves, the leaves curl in on themselves and become hard; this protective cocoon of sorts provides a sanctuary to the eggs laid by adults and defends all of the insects from predation. With prolonged thrip infestation, the leaves become yellow or brown and may drop prematurely. Thrips that fall onto people occasionally bite.
For ornamental indoor trees, the best way to rid the plant of thrips is to pick every infested leaf and discard them outside. Wear gloves while doing this so the bugs won’t bite you. Three known insects feed on Cuban laurel thrips and can rid outdoor ficus trees of infestation; these are Macrotracheliella laevis, Montandoniola moraguesi and Cardiastethus rugicollis
A common pest for many plant species, aphids are tiny but visible with the naked eye and can be white, yellow, brown, black or even blue in colour. With sucking mouth parts, they tap into leaves for sap that they convert into honeydew, which in turn attracts ants. The ants protect the aphids from predators to maintain their supply of honeydew. An aphid infestation manifests itself in dried-out leaves that fall prematurely, but you should see them without trouble. You will also see ants all over your ficus.
Ladybirds work very well at lessening the number of aphids, though they may not eliminate all of them, as the ants will do their best to fend off the ladybirds. You can buy frozen ladybirds at nurseries or feed and grain stores; when they defrost, they come to life. To kill all aphids, add 2 tsp of dish soap, 1 cup of vegetable or white mineral oil and 2 cups of water to a spray bottle and coat the entire plant. This will suffocate the bugs. Make sure you keep the tree in shade while doing this, as the oil may magnify sunlight and harm the leaves. Rinse the plant with water once the bugs are gone.
These microscopic insects most often feed on indoor ornamental ficus trees, particularly the variegated weeping fig. The bugs construct a shell around themselves while feeding that looks like a brown or black bump on the leaf; some of these are hard, some soft and sticky. As they feed, scale bugs leave behind yellowish splotches and convert sap drawn from the leaves into honeydew, as do aphids, though scale do not normally attract ants as aphids do.
Crush every shell you find on your tree to kill the scale. This is effective, but only if you find them all; it’s also a messy and unpleasant task. You can also mix a teaspoon of dish soap with 2 cups of warm water and use a plant sprayer to coat the entire plant (this will not harm the plant, but will kill the bugs); or try a combination of 1/2 tsp of soap mixed with 1/4 cup rubbing alcohol and 1 1/2 cups warm water. Once the bugs are dead, rinse the ficus with water alone.