Spider mites are not insects, but tiny arachnids closely related to spiders. Spider mites pierce individual plant cells and remove the contents, resulting in yellow or white spots. As the number of feeding spots increases, your ficus tree's foliage will turn yellow or bronze and drop off. The main part of their nest is usually where the most damage has been established. Spider mites prefer to reproduce in a warm, dry climate. Keep your plants misted and well-watered to avoid the problem. If you do find a mite infestation, use a miticide for the most effective control.
Check that the problem is spider mites. If you see yellow or bronze leaves, look at the bottom of the foliage for a fine silk webbing that collects dust and looks dirty.
Use a hose (or your shower, if it's winter) to spray a forceful jet of water on all the leaves.
Isolate your infected plant from other plants. Place a humidifier nearby to raise the humidity. Spider mites thrive in dry climates.
Combine a 1 to 1 mixture of rubbing alcohol and water, and spray the foliage once a week for three to six weeks. Focus heavily on the bottom of the leaves.
Use a so-called "soft" pesticide if the alcohol mixture does not work effectively. Soft pesticides include insecticidal oils and soaps. Use the oil at a 1 percent to 2 percent rate during the summer, and a 3 percent to 4 percent rate in the fall, winter and spring for eggs and dormant adults. Try the soaps during the warm season.
Use a chemical pesticide as a last resort. Because spider mites aren't usually killed by regular insecticides, check the label to see if it contains a miticide. According to the Ohio State University Horticulture and Crop Science Department, pesticides claiming "for mite suppression" are usually weak miticides and will not perform well.