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Whenever I buy or am given a houseplant it seems to go downhill from there. I become painfully aware when I see how well others do with plants, knowing I have a lot to learn. When houseplants are not doing well it is usually because of too much or not enough water, or insufficient light. This weakens the plant and opens the door to insects and disease. The secret to controlling insets is knowing the enemy. The more you know about the problem, the better the chance of controlling it.

Aphids are not fussy, as they will feast on anything that is green. They are usually wingless, but not always. They can be green, brown, black, yellow, red, or grey and they colonize plants on tender stems and on the undersides of leaves. Aphids multiply quickly, but spread to other plants quite slowly. The sticky substance they leave is called honeydew that coats the leaves, causing the leaves to turn black with a fungus called sooty mold. Infected plant parts turn pale or yellow and often twist or curl under. Applying water to the underside of the leaves getting rid of the honeydew is usually enough to control them. For faster results use insecticidal soap and repeat if needed.

Mealybugs are small oval insects, usually pink or grey, but have a heavy waxy substance that look like cotton tuffs. Their egg masses look like cotton also. They bunch up where the leaf meets the stem and on the underside of the leaves. Like aphids, they also produce honeydew that leads to sooty mold. Infected plant parts wither and turn yellow. To control Mealybugs, cotton swab with rubbing alcohol or spray the plant with insecticidal soap.

The most common indoor pests are spider mites, that thrive in hot and dry air. They are found on the underside of the leaves and cause yellow spots that look like a yellow tinge. As the mite numbers increase the leaves turn yellow-brown and appear dusty. One can find out if your plants have mites by taking a sheet of white paper under a leaf and tap on it. If tiny particles of moving dust fall on the paper, you have spider mites. Treat by increasing the humidity and spraying the underside of leaves with water. If the plant is severely infected wash the entire plant with water and treat every five days with insecticidal soap until no mites are found.

The easiest houseplant insects to spot are whiteflies because they resemble flying dandruff. They move very fast and they can spread rapidly. Both the larvae and adults produce sticky honeydew and both suck out sap. Due to their speed and mobility they can carry dangerous plant viruses. Always treat whiteflies at night when they are not flying. First vacuum and then spray weekly with insecticidal soap. Use yellow colored pest strips to pick up stragglers.

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