Without good, clean potting soil, your container plants will not likely thrive. Soil is often a haven and breeding ground for insects, weeds and disease. Start your plants off right with high-quality potting soil or make your own with equal amounts of store-purchased topsoil, sand or perlite and peat moss. Over time, if your plants do not thrive, it may be something in your soil and you will have to remedy the situation to save your plants.
Kill fungus gnats that may be breeding in your potting soil. According to the University of Illinois, stop watering your plant and allow your soil to dry out as much as possible. Water again before your plant begins to wilt. The eggs and larvae will die when there is no moisture for them to thrive.
Kill other insects, such a spittlebugs, spider mites and aphids that may be breeding in your soil, with an insecticidal soap or pesticide. Take a sample bug or damaged leaf to a county extension office or nursery for diagnosis, if necessary. Choose a product designed to kill the specific insect and follow label instructions for proper use.
Avoid over-watering. Many diseases and insects in potting soils are caused simply by over-watering your plants. Allow your soil to dry out between waterings and always use containers with drainage holes. If your soil is compact and does not drain moisture well, repot your plant in new potting soil.
Remove the plant, shake and wash off the excess soil, and replant in new potting soil. Starting anew may be the best solution. Sterilize the container first with a bleach-water solution that contains 10 percent bleach to remove any harboring disease or insects.