Fungus and bacteria are the primary suspects when it comes to spots on a houseplant's leaves. If the spots vary in color from yellow to brown to black, then fungus is most certainly the cause. If the tips of the leaves are brown or dry, weathered brown spots can appear on broad-leafed plants. This problem may not be infestation but location. Luckily, this is an easy fix. With the proper care, the plant will grow and thrive.
Determine the cause of the spots. Check the light available to the plant. Feel for drafts, and monitor the area's temperature. Search the topsoil for any white, salty deposits. Examine the pot for sitting water.
Relocate the plant if the plant's in a drafty location, a hot location or a location with direct sunlight. When captured in water droplets on the leaf's surface, direct sunlight can burn leaves. Drafts dry out a plant and contribute to low humidity levels and brown spots. Heat stress can also cause brown-tipped leaves.
Repot the plant with fresh potting soil if the current soil is saturated or the plant has been sitting in water. Excess water causes the buildup of salt deposits. Too much saline can cause brown leaves.
Tent the plant if the soil is dry, the leaves are warm or the humidity level of the room is low.
Insert Popsicle sticks, wooden skewers or any other kind of support suitable for the plant's size and container. Surround the container with clinging plastic wrap. Extend the wrap onto the supports and around the plant.
Mist the plant at least twice a day to promote condensation and humidity.
Monitor new growth for spots.
Trim off brown and spotted leaves when the new growth matures.