Look for juvenile whiteflies on the underside of foliage.
Scale insects weaken a coffee plant.
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.