Insects on indoor plants are usually noticed when the plant is being watered. Adult insects will often fly out of the plant or be drawn to the surface when water is poured onto the plant. Indoor plants can tolerate small infections caused by insects but when it progresses to a large infestation, problems arise. The plant develops discolorations and holes, or becomes brown or yellow, starts to wilt and eventually may die if no action is taken. Insecticidal soap spray is an effective standby and will work on all but the most rampant infestations. In that case, the plant may have to be destroyed. Cleanliness and proper air circulation around the plant helps to forestall many insect problems in indoor plants.
Spider mites are tiny and red and very difficult to spot, but the damage they cause is anything but small. They suck the sap out of new leaves, leaving behind small holes. The mites multiply, the leaves start falling and the plant turns yellow and dies. Infected plants may turn bronze in color and a whitish webbing may also be noticed on the plant. A soap and water spray will help to control minor infections but plants that are heavily infested may have to be destroyed. New mites are produced every three days to a week so spraying each day is absolutely necessary.
Scale insects have shells and are brown in color. They are difficult to spot on a plant even though they clump together on the underside of leaves and on stems. A scale infection is usually only noticed when leaves start developing black spots and branches and leaves start to die. The insects secrete a sticky fluid which causes a black mold to start growing on the plant. Scale is a slow-spreading infection. If pesticides are applied onto the leaves and the roots every two to three weeks, the infection may be halted.
Whiteflies and Mealybugs
If a plant is infected with adult whiteflies it will probably need to be destroyed since they will just fly away when a spray is used. It is easier to control an infestation when the whitefly is in its immature stage and immobile. At this point it looks like scale and can be sprayed with insecticidal soap. Infected plants turn yellow and leaves start growing in a deformed, cup-like shape. Mealy bugs grow quickly and suck the sap from plant stems and leaves. They are white or pink or release a white substance that sticks to the plant and looks like cotton. A black mold often starts growing on infected plants and the plants slowly start to die. Mealybugs are difficult to control since the waxy substance protects them against sprays. They can be killed, however, by brushing individual bugs with a cotton-tipped stick dipped in rubbing alcohol.
Thrips are tiny light brown insects that delve into the soil when disturbed, hence they are difficult to spot. They bore holes in leaves and suck out plant juices causing new buds and leaves to look disfigured. If they are disturbed, adult thrips will fly off and attack other plants, so keep infected plants away from healthy ones. Spraying a soap and water solution onto thrip-infected plants should solve the problem. Thrips also like the color yellow. So, spreading a sticky oil on yellow cards and placing them around the plants is often successful in trapping the thrips.
Aphids are common house plant pests. They are pale green, black or red and can be found in clusters on succulent new stems and leaves. They suck out the juices from the plant, causing it to shrivel and grow stunted with deformed and scrunched-up leaves. Aphids also exude a sticky substance that can cover the plant. Lady bugs love eating aphids but since this is not a viable solution indoors, spraying a diluted solution of soap and water directly on the aphid clusters will cause them to dry up and die. Diluted soap and water does not harm the plant.