Some plants come from the retailer with pests and others acquire them from the environment to which they are located. According to the North Carolina Cooperative Extension---a joint service of North Carolina State University and A&T State University---it is a good idea to quarantine your new plant, keeping it from those already in your home, for 10 days after purchase. This ensures that if the plant brought pests home they won't migrate to others nearby.
Scale insects usually don't look like bugs but just bumps on the leaves and/or stems. They tend to visibly cluster together and cause leaf spotting and drop. Scale spreads relatively slowly and can sometimes be controlled by removal of infected sections; if the infestation is large, destroy it with root or foliar pesticides as recommended by your local cooperative extension or nursery.
These puffy pink or white bugs are tiny but visible and leave a trace of their activity, small white cotton ball-like blobs of wax secretion and white spots. Their infestation is characterized by leaf drop and development of a secondary mold infection. Mealy bugs can take over your indoor plantings very quickly, so isolate or dispose of the plant promptly if the infestation is a large one. Small colonies can be eradicated by a program of diluted alcohol washes followed by systemic root or foliar spray insecticides.
Spider and eriophyid mites are the most common indoor pests. Spider mites suck the life out of plant leaves through tiny punctures. Their damage manifests first as yellow spots, then the leaves turn to bronze and brown and drop from the plant. Although the mites are hard to see, they produce a very fine webbing that is noticeable in a large infestation. Eriophyids, on the other hand, get into leaf and flower buds where their feeding results in misshapen, curled and stunted leaves and petals. They are almost impossible to spot because they are both transparent and hidden. Both types of mites are difficult to eliminate but can be controlled with a program of soapy washes, constantly moist soil, low light, lack of fertilizer and indoor-use foliar miticide.
These tiny winged pests look like moths in their flight stage. Yellowing of the entire plant and leaf cupping are indications of whitefly infestation; an infestation can be terminal for the host plant. They are almost impossible to destroy because they are pesticide resistant, but can be controlled somewhat with sticky fly trap material.
Aphids can be black, red or green and have ridged, humped backs. They suck juices out of plants leaving them with curled leaves and stunted growth. Use warm soapy water washes followed with freshwater rinses to control aphids; if that doesn't work, it is wise to destroy the plant to prevent aphid migration to healthy plants.