Several types of diseases and infestations can cause brown spots on plants. The spots may do nothing but affect the appearance of the plant. However, the spots can also indicate a more serious disease such as late blight disease, which causes some plants to shrivel up and die. Once you've identified the problem, it's important to treat the spots.
Determine whether the plant is infested with insects or pests. Look over the stems and leaves for small webs that point to spider mites. There may also be white scales from sucking insect that hang on the plant stem. Wash the plant in warm, soapy water or apply an insecticide to kill pests.
Evaluate your watering practices. Water on the leaves and stems, for example, can cause leaf blight. Often, a lack of water results in brown spots on house plants. The spots will be most evident on leaves and leaf tips.
Remove all damaged foliage with pruning shears. Bury the diseased leaves and stems or put them in a plastic bag and discard. Do not put them in a compost pile because they can live and spread there.
Provide an adequate amount of water for the plant. Check the soil often and do not oversaturate.
Look for moldy or crusty soil at the very top of the plant container. This may point to fungus or bacteria that causes brown leaf spots. Repot the plant or take the top 1 inch of soil out of the pot and replace it with fresh soil. Water the soil until moist but do not oversaturate.