Might Your Houseplants Have Mites?

By Catherine Wachs

If your potted plants are looking a little sorry right now — wilting, new growth shriveling or a general lack of unhappiness — it could be short winter days or dry heat. Or it might be minuscule troublemakers: spider mites. These tiny creatures, less than a millimeter in size, are not easily seen. The best way to check for them is to examine the plant in a sunny window or a strong backlight. If you see fine webbing, especially in the crotches of the stems or on new growth, it’s a sure sign your plant is under attack. The mites suck on the plant sap, causing stilted new growth and deformed leaves. Infested plants will start to turn brown. If left unchecked, mites could destroy a whole houseplant.

An easy, non-toxic remedy is to mix a scant teaspoon of dish liquid with 12 ounces of water in a spray bottle (more soap is not better). Just plain old dish liquid will do. It kills the critters by penetrating their cell membranes, causing the insect to dry out. Make sure the soap is well mixed into the water and spray wherever you see the webbing, checking under the leaves for more culprits. Leave the soap solution on overnight. If it’s a hairy or fuzzy-leaved plant, like a violet, dilute the solution by half and test the spray on one leaf first, to make sure it doesn’t burn the leaf. If the leaf turns brown after 2 days, email me for other options.

Check your plants every 3 days. The mites will return. Repeat the process until the mites are eliminated. Wash, wipe or spray the soap off with plain water after 2 treatments, since the soap film is not ideal for the plant.

There’s no way to prevent mites from visiting. They float in on air currents, or hitchhike on cut flowers. Any insect usually attacks a stressed plant first. Spider mites become especially active in dry, dusty conditions. So keep your houseplants happy by misting every one in a while, watering properly (most plants are killed by over-watering) and making sure they are getting enough light and nutrients. I feed my plants by applying a scoop of organic compost on top of the dirt, but there are many commercial fertilizers, too. Just use half the recommended amount, to prevent “burning” plants with too much fertilizer.

If you are the “live and live” type, any spiders you find in the house can be deposited on the plant and they can do future pest control for you. Spiders are invaluable in this role, inside and outside your home (if only they weren’t so scary-looking).