Always spray the underside of leaves to get better control of insect pests. Dr. Frank Hale, an insect specialist with the University of Tennessee Agricultural Extension Service, shares tips on battling insects that plague houseplants. Mealybugs, common indoor pests, thrive in high temperatures and low humidity. They appear as a cottony substance at a plant's leaf joints and on the underside of leaves. Mealybugs, aphids and whiteflies have piercing, sucking mouth parts and if uncontrolled can suck the life from the host plant.
Mealybugs are easy to control by applying soapy water with a sponge or a spray bottle.
To treat recurring problems, apply isopropyl alcohol with cotton swabs to infested areas of the plant. Whitefly can also be a problem for indoor plants. Yellow sticky traps are effective controls when the insects begin to fly. Tiny black insects, fungus gnats hop around the surface of the soil. They're easily controlled with a soil drench of the bacterium Bt, or Bacillus thuringiensis .