Beginner’s Guide to Houseplant Pests | Rentokil

Houseplant Pests: A Beginner’s Guide to Identification, Damage, and Treatment

Bringing the outdoors in with houseplants is a wonderful way to connect with nature and brighten your home. But these green companions can sometimes attract unwelcome guests. This guide focuses on identifying common houseplant pests, understanding the specific damage they cause, and outlining effective treatment strategies.

Know Your Enemy: A Detailed Look at Houseplant Pests

Accurate identification is the cornerstone of effective pest management. Here’s a detailed look at the most common culprits:

• Aphids: These tiny (1-4mm), pear-shaped insects come in various colours (green, black, pink, white). They cluster on new growth, sucking sap and causing:
  • Damage: Distorted, curled, or stunted growth, especially on new shoots and buds. Leaves may turn yellow and drop. They excrete sticky honeydew, attracting ants and promoting sooty mould (a black fungus).Identification: Look for clusters of small insects, often on the undersides of leaves or stems. Honeydew is a telltale sign.
  • Treatment:
    – Manual Removal: Wipe or gently wash off aphids with a damp cloth or cotton swab dipped in soapy water.
    – Insecticidal Soap: Spray affected areas thoroughly, ensuring contact with the aphids. Repeat as needed.
    – Biological Control: Introduce ladybirds or lacewings as natural aphid predators.
    
    

• Fungus Gnats: Small (2-3mm), dark flies seen hovering around plant soil. The adults are more of a nuisance; the larvae cause the damage.
  
  
  • Damage: Larvae feed on roots, causing root rot, stunted growth, and weakened plants. Plants may wilt and become more susceptible to other diseases.Identification: Look for small flies near the soil surface. Larvae are small, white, legless grubs in the soil.
  • Treatment:
    – Allow Soil to Dry: Fungus gnats thrive in moist soil. Allow the top inch or two of soil to dry out between waterings.
    – Yellow Sticky Traps: These can trap adult gnats, reducing their numbers.
    – Bti (Bacillus thuringiensis israelensis): A biological insecticide that targets gnat larvae in the soil. Mix with water and apply as a soil drench.

• Mealybugs: Small (3-5mm), white, cotton-like insects, often found in clusters on leaves, stems, and leaf axils. They have a waxy coating that protects them.
  
  
  • Damage: Mealybugs suck sap, causing yellowing, wilting, and leaf drop. They also produce honeydew, leading to sooty mould. Heavy infestations can kill plants.
  • Identification: Easily recognisable by their white, cottony masses.
  • Treatment:
  • Manual Removal: Use a cotton swab dipped in surgical spirit to dab directly onto mealybugs.
  • Horticultural Oil: Can suffocate mealybugs. Apply according to product instructions.
  • Systemic Insecticides: For severe infestations, a systemic insecticide may be necessary. Follow product instructions carefully.

• Spider Mites: Tiny (less than 1mm), eight-legged arachnids, nearly invisible to the naked eye. Their presence is often first noticed by the fine webbing they create on the undersides of leaves.
  
  
  • Damage: Spider mites suck sap, causing yellow or white stippling on leaves. Heavy infestations can lead to bronzing, leaf drop, and even plant death.
  • Identification: Look for fine webbing and tiny moving dots on the undersides of leaves. Use a magnifying glass if needed.
  • Treatment:
    – Increase Humidity: Spider mites prefer dry conditions. Misting plants or using a humidifier can help.
    – Insecticidal Soap: Effective if applied thoroughly, ensuring contact with the mites.
    – Predatory Mites: Introduce predatory mites that feed on spider mites.
    

• Scale Insects: Small (1-5mm), flat insects that resemble bumps or shells attached to leaves and stems. They can be brown, black, or white.
  
  
  • Damage: Scale insects suck sap, causing yellowing leaves, stunted growth, and sometimes plant death. They produce honeydew, which can lead to sooty mould.
  • Identification: Look for small, immobile bumps on leaves and stems.
  • Treatment:
    – Manual Removal: Scrape off scale insects with a fingernail or a cotton swab dipped in surgical spirit.
    – Horticultural Oil: Can be effective against scale insects in their crawler stage.
    – Systemic Insecticides: May be necessary for severe infestations.

• Thrips (Thunder flies): Tiny (1-2mm), slender insects with fringed wings. They can be difficult to spot.
  
  
  • Damage: Thrips feed on plant tissue, causing silvery or distorted leaves, and can transmit plant viruses. They may leave small black droppings.
  • Identification: Look for tiny, fast-moving insects on leaves and flowers.
  • Treatment:
    – Insecticidal Soap: Effective if applied thoroughly.
    – Blue Sticky Traps: Can attract and trap thrips.
    
    
    

• Whiteflies: Small (1-2mm), white, flying insects that cluster on leaf undersides.
  
  
  • Damage: Whiteflies suck sap, spread plant diseases, and produce honeydew. Heavy infestations can weaken plants and cause yellowing and leaf drop.
  • Identification: Easily recognised by their small size and white colour.
  • Treatment:
    – Yellow Sticky Traps: Attract and trap whiteflies.
    – Insecticidal Soap: Effective if applied thoroughly.

• Springtails: Tiny (1-3mm), wingless insects that live in the soil. They’re generally harmless, feeding on decaying matter.
  
  
  • Damage: None directly to plants, but their presence in large numbers indicates overwatering or poor drainage.
  • Identification: Small, jumping insects in the soil.
  • Treatment: Address the underlying moisture issue by allowing the soil to dry out between waterings.

• Root Aphids: Small (1-2mm), white aphids that live in the soil and feed on roots.
  
  
  • Damage: Wilting, stunted growth, and general decline of the plant.
  • Identification: Difficult to see without removing the plant from its pot.
  • Treatment:
    – Repotting: Repot the plant with a fresh potting mix, ensuring all old soil is removed from the roots.
    – Systemic Insecticides: May be necessary for severe infestations.

Important Considerations:

• Prevention: Inspect new plants before bringing them home. Quarantine new plants for a few weeks to monitor for pests.
• Early Detection: The earlier you identify a pest problem, the easier it will be to treat.
• Repeat Treatments: Treatments may need to be repeated to be effective, especially for pests with multiple life stages.
• Consider Beneficial Insects: Introducing natural predators can be a sustainable way to control some pests.
• If Infestations Persist: If you’ve tried various treatments and the infestation persists, consider consulting a professional who can identify the specific pest and recommend the most effective course of action.