How to control indoor plant pests without toxic chemicals

Last Updated: 
February 15, 2008

CORVALLIS, Ore. – Winter is a good time to check indoor plants for pests including mites, thrips, mealybugs, scales, whiteflies and aphids.

Oregon State University Extension entomologists suggest a number of "integrated pest management" strategies to keep your indoor pest populations at bay without resorting to toxic chemical controls.

First of all, learn your houseplants’ needs and keep them healthy with adequate light, water and fertilizer. Stressed plants encourage pest problems. For example, high nitrogen favors aphids, dry and dusty conditions promote mite outbreaks.

Isolate infested plants from others so they don’t spread from plant to plant. If whiteflies are present, you can vacuum them off. Then freeze the bag contents.

Place aluminum foil around the base of a plant. This may disorient winged pests like thrips and aphids and prevent them from landing. Try beneficial fungi for aphids. Commercial products are available. Paint a small dish yellow and fill it with water to attract and drown winged aphids and thrips.

Use yellow sticky traps, available at garden centers, for winged aphids. Blue sticky traps are good for detecting adult thrips. White sticky traps work best for fungus gnat control.

In a greenhouse setting, you can purchase and release parasitic wasps for control of soft-bodied pests.

Larger insect pests can be easily eliminated by hand if you are not too squeamish. Many of these are most active at night, so capturing them by hand is best done after dark with a flashlight.

Swabbing your infested plants with a watercolor paintbrush dipped in rubbing alcohol can destroy tiny soft-bodied plant pests such as aphids and mealybugs. This works best with small infestations.

Remove and destroy plant parts that are totally infested, if you can’t or don’t want to remove pests in any other way. Discard infested soil and clean the pot or container as well. If an entire plant is badly infested, think about getting rid of it.

Spray plants infested with soft-bodied pests with soapy water. This may hurt some plants, so test one leaf first. Also, it is not as effective on winged adults, because they can leave and come back later.

If you feel you have to resort to chemical pesticides, keep in mind that few pesticides are registered or considered safe for indoor use on houseplants. Read labels carefully for where and how to use a pesticide. If indoor use is not listed on the label, take the plant to be treated outside, away from children and pet traffic areas. Leave the plant outside a day or two after spraying.

Author: Carol Savonen
Source: Amy Dreves