When house plants show signs of deteriorating health, check to see if the problem comes from an insect infestation. Symptoms of invading house plant bugs include mottled or speckled leaves, holes in leaves, stem wilting, and visible eggs and insects. You may need to use a magnifying glass when looking at leaves and stems to spot the more minute insects. Thrips, aphids, scale insects, mealy bugs, aphids, fungus gnats and spider mites are the most common house plant bugs.
Hang non-toxic sticky cards or boards on branches or plant them into the soil. They'll attract and kill off fungus gnats, aphids, thrips and white flies. When dead insects cover the traps, remove and throw them away.
Insecticidal soap spray needs to be applied approximately once or twice a week to be effective in killing aphids, thrips, mealy bugs, white flies and spider mites. Spray leaves, stems and the soil for best results.
Mealy bugs at the roots can be hard to kill. Short of discarding the plant, your best shot at getting rid of them is carefully washing the roots in water to rinse them off and then place the plant into a new, clean pot. You can also gently hose off aphids or washed them off in a bath tub or large sink.
Dissolve 1/2 tsp. of liquid dish detergent in one quart of warm water. Dip a soft cloth or cotton swab into the solution and wipe clean the leaves and stems of smooth-leaf plants. Don't forget to clean the bottom of the leaves too.
While soft scale insects with waxy shells will succumb to other methods, an insecticide is better used against the hard armored scale insect. Miticide controls infestation of spider mites. For harmful fungus gnats on seedlings and young plants, drench the soil with the bacillus thuringiensis insecticide (Bti), a substance that is made from over 35 kinds of bacteria to control caterpillars and flying insect larvae.
Non-toxic neem oil kills thrips, aphids, white flies and soft scale insects. Dissolve 2 tbsp. of oil into one quart of warm water and put in a spray bottle. Then add 1 tsp. of dish soap and spray the infected plant and the soil thoroughly. Repeat once a week until all insects are destroyed.
Some house bugs have natural predators you can introduce to in order to kill off the pests. For example, predatory mites, ladybugs or flower bugs will get rid of spider mites.