How can you stop a ficus tree from releasing a sticky film on the floor?

Ficus trees

Check for spider-mites. Put a clean, white piece of paper on the floor, shake the branches above the paper then look at the dust on the paper. If the dust particles start to move around, you have spider-mites. Spider-mites make small holes in the leaves to suck out some sap. The sap continues to leak for a while, until the tree can close off the leak, and that's how you get the mess on the floor.

If possible, take the tree outside, spray it off paying particular attention to the bottom of the leaves. Repeat this process every few days for a while and see if you can reduce the problem. If you have any other houseplants, they too are probably affected, just not as noticeable. Ficus can be rinsed off, but some other plants can't. It might be necessary to use an insecticide on other plants. Check with local plant specialists, but realize that it won't do any good to get rid of the pests on your ficus without taking care of the other plants.

Another thing I do when dealing with spider mites, is to replace some of the soil in the top of the pot with clean potting soil. Before you hose down your ficus, scoop out as much of the top layer of soil as you can and replace with fresh potting soil (I use the organic potting soil that is widely available even at Walmart) and then hose the ficus. If it is cold out where you live, you can put the ficus in the shower. It is a wet operation. You want to make sure to turn the branches as much as you can to rinse off the undersides of the leaves where the spider mites hide. Usually ficus are too large for application with insecticidal soaps, which are also effective but the showering is very effective though it might need to be done several times a month to really eradicate them. Also keep in mind that spider mites like low humidity so you will want to increase the humidity around this plant. Place the pot on a tray of pebbles and fill the tray with water. Mist your ficus if possible, making sure to get the undersides of leaves. This will somewhat help prevent an infestation from recurring.

Also, check the soil for soil mealy bugs, they leave a white film in the soil that looks like powder, check to see if there are small white rice looking critters with a white film around them.