How can I get rid of the spider mites that are killing my houseplants? —Tammy Parchem, Burlington, ON, Canada
Keeping houseplants free of mites can be a challenge, especially mite-prone plants such as ivy and palms. Clean foliage regularly—both the undersides and tops—and spray with insecticidal soap the moment you see spider mite activity. If repeated applications don’t work, spray with an insecticide containing bifenthrin.
For severe infestations, you’ll have to take more drastic measures. If most of the plant is covered with spider mites and fine webbing, throw it out or prune it back nearly to the soil. Mites congregate on leaves and stems rather than roots, so new growth coming from the roots probably won’t be infested. (Make sure any parts left after pruning are free of mites.) This approach will not work with palms, since they grow only from the very top. Pruning them back will destroy them.