Managing insects on indoor plants (2024)

Many insect problems on indoor plants can be managed using nonchemical methods, particularly if the infestation is minor.

Washing

• Wipe leaves with a damp paper towel, changing towels often to prevent spread.
• Spray small plants in a sink.
• Spray large plants in a shower.

Physically remove pests

• Handpick large pests such as earwigs, caterpillars, slugs and millipedes.
• Small numbers of scale insects can be removed using a fingernail file or something similar.
• Mealybugs can be removed using tweezers or a cotton swab dipped in alcohol.
• Some pests can be removed using a forceful spray of water.
• Repot with new potting soil to eliminate soil-borne pests. Use clean pots and wash soil off plant roots.

Pruning

• Prune if a pest issue is isolated to a few leaves, stems or branches.
• When infestations are more widespread, prune the most severely infested plant parts. This makes it easier to manage pests on the remaining plant.
• In the case of severe infestations and depending on the type of plant, cutting it back may help eliminate pests.
• Watch new growth for signs of infestation.

Throw away or compost plant

• Necessary and economical if the plant is heavily infested and badly damaged.
• Avoids exposing other plants to the same pest problem.

If you still have an insect problem after trying nonchemical methods, consider using a pesticide. There are a limited number of products available for indoor plants. They are sold at plant nurseries, garden centers, building supply stores and online.

They should contain one of the following active ingredients:

Pyrethrins

• No residual activity, must directly spray the insect to kill it.
• Effective against mealybugs, whiteflies, scales, thrips, aphids.
• Repeat applications usually necessary.

Potassium fatty acids (i.e. insecticidal soap)

• Sold specifically as an insecticide.
• Do not mix homemade soap products as this can burn plants.
• No residual activity, must directly spray the insect to kill it.
• Kills insects by smothering.
• Repeat applications usually necessary.
• Effective against scales, aphids, thrips, spider mites, whiteflies.

Plant oil extracts

(canola, clove, sesame, cottonseed, garlic oils)

• Only kills when sprays cover the insects.
• Kills when insects are smothered.
• Repeat applications usually necessary.
• Effective against scales, thrips, aphids, whiteflies, spider mites.

Neem oil

• Disrupts insect growth.
• Short to medium residual activity, lasts days or weeks.
• Repeat applications usually necessary.
• Effective against whiteflies, thrips, aphids.

Bacillus thuringiensis, subspecies israelensis, strain AM 65-52

(e.g. Knock Out Gnats)

• Applied to soil.
• Bacteria that specifically attack fungus gnat larvae.
• Not effective against fungus gnat adults.
• Available primarily online.

Imidacloprid

• Systemic, i.e. taken up and moved throughout the plant.
• Long residual activity, lasts months.
• CAUTION: Toxic to bees; do not use on bee attractive plants that are set outside during the summer.
• Effective against mealybugs, soft scales, aphids, whiteflies.

Precautions:

• Be sure the plant you are treating is listed on the product label.
• If you use a product that requires to be diluted with water, mix only as much as you expect to use in one day. Be sure to use it that day.
• Apply chemicals outdoors whenever possible.
• In cold weather, spray plants indoors in a well-ventilated area.
  • To prevent secondary exposure from pesticides, enclose your plant in a plastic bag and seal shut.
  • Cut a small hole in the side of the bag and insert your spray nozzle.
  • Move the nozzle around to spray your plant thoroughly, especially under the leaves.
  • Remove the spray nozzle and quickly cover the hole with duct tape.
  • Keep it out of direct sun till dry after treatment.
• Never use any pesticide on a plant that is moisture-stressed. Water the soil a day or two before applying pesticides.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Adults secrete waxy shell-like coverings.
• Usually brown, grayor white.
• Round, ovalor oyster shell-shaped, 1/16 to 1/8 inch in diameter.
• Two types of scales:
  • Soft scales are most common, about 1/8 – ¼ inch long.They produce honeydew (a shiny, sticky secretion).
  • Armored scales are about 1/16 – 1/8 inch long.They do not produce honeydew.
  • Both types of scales produce tiny crawlers that have legs and are mobile.

Damage

• Use sucking mouthparts to feed on plant sap.

• Heavy feeding causes leaves to yellow and drop, slows growth and stunts plants.

Detection

• Watch for discolored leaves.

• Watch for honeydew (a shiny, sticky substance).

• Examine plant stems and the undersides of leaves, especially along mid-veins, for presence of scales.

Management

• Washing.

• Physical removal: use a fingernail file or something similar.

• Pesticides:horticultural oils, insecticidal soaps, pyrethrins, imidacloprid.
  (CAUTION:Imidacloprid is toxic to bees; do not use on bee attractive plants that are set outside during the summer.)

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Soft-bodied insects, about 3/16 inch long.
• White, powdery, waxy secretions cover their bodies.
• Have white filaments sticking out along the sides of the body and at the tail end.

Damage

• Use sucking mouthparts to feed on plant sap.
• Heavy feeding yellows leaves, stunts plants and causes plants to wilt.

Detection

• Watch for discolored leaves.
• Watch for honeydew (a shiny, sticky substance).
• Examine plants:
  • Along veins on the undersides of leaves.
  • At the point where leaves join stems.
• Some mealybugs may also be found below the soil surface on the main stem.

Management

• Washing.
• Physical removal: use tweezers or a cotton swab dipped in alcohol.
• Pesticides: pyrethrins, imidacloprid.
  (CAUTION:Imidacloprid is toxic to bees; do not use on bee attractive plants that are set outside during the summer.)

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Adults:Very small, about 1/16 inch long,white gnat-like insects.
• Immature:Less than 1/16 inch long; flat, oval, scale-like.
• All stages are normally found on the undersides of leaves.

Plant damage

• All stages feed on plant sap, using their piercing-sucking mouthparts.
• Feeding can cause leaves to yellow and drop and reduce plant vigor.

Detection

• Adults cling to plants and are easily disturbed, fluttering up when you water or handle a plant.
• Difficult to spot the immature insects.
• Use yellow cards to capture flying adults.

Management:

• Washing.

• Pesticides: insecticidal soap, neem, plant oil extracts, pyrethrins, imidacloprid.
  (CAUTION:Imidacloprid is toxic to bees; do not use on bee attractive plants that are set outside during the summer.)

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Small, 1/16 - 1/8 inch long.
• Pear-shaped soft-bodies.
• Clearly visiblelegs and antennae.
• Typically green, but may be other colors as well.
• Typically wingless, although winged adults capable of flight maybe present some times.

Damage

• Use sucking mouthparts to feed on plant sap.
• Leaves can yellow and plants can become stunted and distorted.
• Honeydew on leaves that can become black with sooty mold.

Detection

• Watch for discolored leaves.

• Watch for honeydew (a shiny, sticky substance).

• Examine plants for aphids clustered on stems just below flower buds or newly opening leaf buds.

• Also check on flowers and the undersides of leaves.

• Whitish cast skins may also be seen.

Management

• Washing.
• Physical removal: cotton swab dipped in alcohol; remove using a forceful spray of water.
• Pesticides: pyrethrins, insecticidal soap, neem, plant oil extracts, imidacloprid.
  (CAUTION:Imidacloprid is toxic to bees; do not use on bee attractive plants that are set outside during the summer.)

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Very small, about 1/16 inch long and slender.
• Usually tan or dark colored.
• Run quickly when disturbed.
• Adults can fly.

Plant damage

• Thrips feed by scraping leaves or flowers with their rasping mouthparts, then sucking the fluid that is released.

• Damaged leaves develop irregular silvery streaks or splotches.

• Flowers become streaked or distorted.

• You may see small, shiny drops of excrement on leaves,where feeding is heavy.

Detection

• Watch for discolored leaves and flowers.
• Use yellow or blue sticky cards to capture flying adults.

Management

• Washing.
• Pesticides: pyrethrins, insecticidal soap, neem, plant oil extracts.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Very small, about 1/16 inch long.
• Usually slender white or gray insects.
• Springtails jump when they are disturbed.

Damage

• Springtails are scavengers, feeding on decaying roots and fungi.
• They prefer to live in damp potting soil, especially a mix containing a high percentage of peat.
• They rarely, if ever, damage indoor plants.They are mostlya nuisance.

Detection

• Check the soil.
• Springtails are particularly noticeable right after watering the plant.

Management

• Let surface soildry as much as possible between waterings,without letting the plants wilt.
• There are no pesticides to treat springtails.

Appearance

• Adults:
  • Small, 1/16 - 1/8 inch long.
  • Dark-colored with clear wings that are folded behind its back when at rest.
• Larvae:
  • Legless, worm-like larvae.
  • Have dark head.

Plant damage

• Fungus gnats are scavengers with larvae feeding on decaying roots and fungi in soil.
• They prefer to live in damp potting soil, especially a mix with a high percentage of peat.
• They rarely, if ever, damage indoor plants.
• They are mostlya nuisance.

Detection

• Look foradults on plants or adjacent areas (CAUTION: can be confused with fruit flies or other small-sized flies).
• Use yellow sticky cards to capture adults.
• Place a slice of potato on the soil surface and check periodically for larvae.

Management

• Let surface soil dry as much as possible between waterings, without letting the plants wilt.
• Yellow sticky traps will capture some adult flies.But, traps only help to detect adults and should not be relied on as the only management method.
• Bacillus thuringiensis, subspecies israelensis, strain AM 65-52 (e.g. Knock Out Gnats) applied to the soil. It is only effective against larvae.
• Repot with fresh soil in a clean container after washing soil off the plant roots.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• Oval shaped.
• Yellowish or greenish in color.
• 1/50th inch long (magnification is typically required to see them).
• Amber-colored mite eggs, whitish cast skins, and black fecal specks may also be seen.

Damage

• Piercing leaf tissue with needle-like mouthparts, feeding on sap.
• Feeding creates a stippled appearance on the leaves.
• Feeding can also yellow leaves and cause leaf drop.

Detection

• Watch for speckled or mottled discoloration on leaves.Severely infested leaves can look bleached.
• Examine underside of leaves, especially with magnification.
• Tap leaves with a sheet of white paper underneath andwatch for tiny moving creatures.
• Watch for presence of fine webbing.
• Spider mites thrive in dry, warm conditions.

Management

• Washing.
• Wash your hands and any tools after working with infested plants to avoid accidentally spreading them on hands, clothingand watering cans.
• Pesticides: insecticidal soap, plant oil extracts.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Appearance

• These mites are extremely small and semi-transparent.
• Impossible to see without high magnification.

Damage

• Inhabit protected portions of plants, especially young tender leaves, budsand flowers.
• Infested leaves are stunted, brittle and often hairy. Flower buds may be deformed and streaked.
• Sometimes injured leaves, buds and flowers may turn black.
• Stems of infested ivy plants are often leafless or have small hairy leaves.
• Damaged African violets typically have small, cupped hairy leaves in their centers.

Detection

Diagnose cyclamen mite problems by the symptoms.

Management

• Throw away infested plants.
• Pesticides and other methods are not practical options.