Often the first indication of an infestation is after the plant has been affected. If your plant shows signs of stress like color change, leaf drop, or wilting - you may have insects. There can be other reasons for these problems, such as over-watering, under-watering, temperature, lighting, etc. So if you see any of these symptoms, a careful inspection is in order to see if you can find bugs.
you find insects, the next step is to identify
them. There are many resources, many on the Web, to help you to do this. Here are
some of the bugs that you may come across on your plants.
Aphids: These are small (1/16 - 1/8 inches), six legged bugs that pierce plants and suck their juices. They come in a variety of colors including light green, red and black. Aphids can multiply into great numbers quickly, and spread from plant to plant. Damage from aphids includes leaf curling, stunted growth, and distorted leaves. They also produce honeydew, which causes sooty mold. Use insecticidal soap, or if possible, take plants outside and spray with a fairly strong jet of water to remove them.
Whiteflies: These are among the most difficult of all houseplant pests to control. They are hard to see when young and once they mature, can rapidly infest a whole houseful of plants. Whiteflies look like tiny white moths. They are related however, to scale insects. Like scale, they feed by sucking plant juices. With a heavy infestation, the plants yellow and eventually die. They also excrete honeydew, which can lead to another problem, sooty mold fungus. This too can lead to leaf drop. When choosing a product to treat for whiteflies, select one for the specific stage of development they're in. Insecticidal soaps and oil sprays get rid of nymphs while yellow sticky traps can help control adults.
Scale: Scale look like tiny bumps along a plant's stems. Unless you are looking for them or some kind of insect, it's pretty easy to miss them. They're often mistaken as part of the plant. They come in a variety of colors including, tan, black, brown and gray. The scale part of the insect that you see is actually a hard protective covering. The two stages of scale are the adult (hard shell) stage and the crawler stage. The crawlers are the easiest to kill with insecticides, while adults may be very difficult to control. They damage a plant in much the same way as whiteflies, and also leave a sticky excretion that can result in sooty mold.
Spider Mites: these tiny red bugs are not really insects as they have 8 legs and no wings. They are related to arachnids (spiders). With this pest, you'll most often see damage before you see the bug, unless you happen to be looking for them. These guys also leave webbing, which they use with air currents to spread to other plants. Both the nymph and adult stage of spider mites damage plants. The damage is usually seen as speckled coloring, color loss and droopiness. They are difficult to control. Often several integrated steps are needed (including destroying those plants that are heavily infested) for success.