If the soil settles, add more, making sure to leave room at the rim to water. Common Insect Pests of Houseplants Mealybugs look like a mass of cotton. They commonly lodge in the joints between the leaf and the stem or on the undersides of leaves, and they exude a substance called honeydew, which can encourage fungal diseases. Although the treatment is labor-intensive, it's effective. Treat with alcohol as needed.
Aphids reproduce quickly, and infestations can occur overnight.
To treat infestations, spray plants with insecticidal soap, which is safe to use indoors. Make sure to apply the soap to both sides of the leaves. Insecticidal soap won't penetrate the hard shells of mature scale insects. Use a solution of fine horticultural oil to smother them. Follow package directions for combining the oil with water.