Common Pests of Indoor Plants

Scale Insects

Typical damage: Clustered or single green-to- brown disc-like scales under leaves and on stems; also mottling of foliage when seen against the light. Leaves may turn yellow and have a sticky substance on them. Timely attention is essential because bad infestations are difficult to eradicate.

Control measures: Rub off scales with moist cotton swab soaked in rubbing alcohol or—on thick leaves—a soft toothbrush soaked in rubbing alcohol. Check plant for sensitivity by wiping only one leaf and waiting 24 hours to check for adverse reaction. Spray with Horticultural Oil Spray to smother adult insects. Pyrethrin, Neem Oil and Insecticidal Soap will help control the immature crawlers. Systemic Houseplant Insect Control may control both stage. Repeat one week later.

Red Spider Mites

Typical damage: Tiny white or yellow spots on leaves, later becoming a mottled and dusty residue or webbing. Fine webs under leaves and in growing tips. Leaves may curl and dry. Mites thrive in hot, dry weather.

Control measures: Wash with a clean, strong spray of warm water several times over two to three weeks. Also apply a miticide, Horticultural Oil Spray, Neem Oil or Systemic Houseplant Insect Control.

Thrips

Typical damage: Streaked, flecked or distorted leaves and flowers remain after insects have sucked plant juices.

Control measures: Remove flowers and buds on infested plants, as insects hide inside them. Apply Insecticidal Soap as recommended. Control thrips with insecticide containing Pyrethrin, Insecticidal Soap, Neem Oil, Horticultural Oil Spray, or Systematic Houseplant Insect Control.

Note: Insecticidal Soap may be purchased at W&W Nursery & Garden Center, and is composed of potassium salts of fatty acids. It is not the equivalent of the common household dish soap.

Aphids (pictured above)

Typical damage: Green, red/orange or black/ gray insects visibly sucking plant juices. Cause small, distorted, weak growth and leave a sticky, clear residue. Shoot tips and flower buds most susceptible. Control measures: Apply Insecticidal Soap, Pyrethrin, Neem Oil, Horticultural Oil Spray, or Systematic Houseplant Insect Control as recommended.

Fungus Gnat

Typical damage: Harmless tiny black insects fly up when disturbed. Destructive white larvae come to soil surface, feed on nutrients in soil and occasionally on young roots.

Control measures: Water plant less frequently; discard drained water from saucer. Spray soil and plant with Garden Safe Houseplant & Garden Insect Spray. Place a venus flytrap plant near affected plants. Place a sticky trap on the soil to catch adults as they emerge from the soil.

Leaf Miners

Typical damage: Irregular yellow, cream or brown channels across leaves.

Control measures: Spray with Isotox or treat the soil with a granular systemic insecticide.

Whiteflies

Typical damage: Tiny white fly-like insects fly up when plant is disturbed. Larvae suck plant juices, causing general weakening and yellowing. Thrive in dry climates, generally on flowering plants. Can spread rapidly. Timely attention is key.

Control measures: Remove leaves that have a large number of larvae on them. Flying adults can be caught with a vacuum cleaner. Spray with Pyrethrin, Insecticidal Soap, Neem Oil, Horticultural Oil Spray, or Systematic Houseplant Insect Control.

Mealybugs

Typical damage: Cottony white masses along stems and under leaves. Small flat insects move very slowly. Leaves may have a sticky substance on them and be distorted.

Control measures: Kill by wiping or spraying with rubbing alcohol after first checking plant’s tolerance: Apply alcohol to one leaf. Wait 24 hours to check for harmful reaction. Spray Insecticidal Soap, Pyrethrin, Neem Oil, Horticultural Oil, or Systematic Houseplant Insect Control as recommended. Remove cottony masses (egg sacs) from under pot rims, shelving, stakes and under pots.