House plant pests

Aphids 

• Tiny green, brown or black insect often found on the undersides of leaves and on the buds.
• Feeds on plant causing stunted growth, and curled or distorted foliage, produces a sticky sap called honeydew.
• Can be controlled by spraying with a strong stream of water or insecticidal soap.
• Common hosts:  Ornamental peppers, Hibiscus, Mums

Fungus gnats

• Small, dark colored flies that jump and fly across the soil.  Favoring a moist environment, they cause no damage, but create a nuisance as they develop in potting soil.
• Yellow sticky cards can be used to trap adults, also allow soil surface to dry between waterings.  Pyrethrin sprays are also effective on adults.
• Common host:  moist soil

Mealybug 

• Soft bodies, white cottony appearance on stems, undersides of leaves and on buds, also excretes large amounts of honeydew.
• Feeding damage causes stunted plant growth.
• Alcohol on a cotton swab can be applied to the bug, caution:  alcohol may cause leaf burn.  Insecticidal soap and insecticides with pyrethrin are effective.
• Common hosts:  Jade, Coleus, Lantana, Cactus, Citrus trees, Poinsettia

Mites, Spider mites

• Tiny, light-colored arachnids, favor hot dry conditions.
• Produce webbing on foliage and stems, produces distorted yellowish foliage.
• Can be controlled by spraying with a strong stream of water, insecticidal soaps or horticultural oil.
• Common hosts:  Ivy, Dracaena, Figs, Hibiscus, Norfolk Island Pine and Schefflera

Scale

• Oval or round, brown insects, found on stems and leaves.
• Suck plant juices resulting in poor or stunted plant growth, produces sticky honeydew.
• Horticultural oil, or handpicked if few in number.
• Common hosts:  Ficus, Citrus, Ferns, Ivy

Thrips

• Extremely tiny insects, adults are light tan to brown, appear white when young, recognized by the damage they cause.
• Feed on foliage and flowers, causing them to become distorted and discolored, create silvery areas on leaf surface, and scarring of petals.  May transmit viruses.
• Yellow or blue sticky traps may attract adults.  Difficult to treat when inside the plant parts, exposed thrips may be controlled by soaps and oil sprays.

Whitefly

• Small, white, gnatlike insect.
• Adults and young feed on leaves, causing the leaves to turn pale yellow or white.
• Yellow sticky cards can be used to trap adults, insecticides containing pyrethrins is effective on adults, horticultural oil, neem insecticides and insecticidal soaps are useful on nymphs.
• Common hosts:  Ivy, Lantana, Verbena, Hibiscus, Poinsettia, Tomato, Cucumber

Credits:

W.S. Cranshaw - Colorado State University Extension

Mary Concklin and Kathleen M. Kelley - Consumer Horticultural Center at Penn State