Glasshouse whitefly is a common sap-feeding insect, mainly found on houseplants but can be very common in the greenhouse where temperatures are high. They excrete a sticky substance (honeydew) on foliage, which allows the growth of sooty moulds.
Common name Glasshouse whitefly or Trialeurodes vaporariorum
Plants affected Many houseplants and greenhouse plants
Symptoms Sticky honeydew on foliage, black sooty moulds, small white-winged insects
Active All year round
Glasshouse whitefly is a sap-sucking insect that can reducs the vigour of plants and excretes a sticky, sugary substance, called honeydew, on the leaves, stems and fruits of its host plants. It attacks many vegetables and ornamental plants grown in greenhouses as well as houseplants. These include: cucumber, melon, tomato, peppers, Chrysanthemum, Gerbera, Pelargonium, Fuchsia, Lantana, poinsettia and Verbena. Outdoor plants can also be attacked but not to such a damaging degree. Note that whiteflies seen on brassicas, Viburnum tinus, honeysuckle, evergreen azalea and rhododendron are other species of whitefly specific to those plants.
It thrives in warm conditions, which is why it is not usually a problem on outdoor plants. Glasshouse whitefly is active all year round on houseplants and in greenhouses.
You may see the following symptoms:
It is relatively easy to see whiteflies on infested plants. When a plant is disturbed clouds of small white-winged insects, 1.5mm (about 1/16in) long, will fly up this distinguished
infestation from other insect such as aphids
You may also see flat, oval, creamy white scale-like nymphs on the underside of leaves
Adult whitefly and the nymphs excrete sticky honeydew on the foliage, stems and fruits, which allows the growth of black sooty moulds
Healthy Plants: Maintain plant health through proper watering, fertilizing, and pruning. Healthy plants are less susceptible to whitefly infestations.
Inspect New Plants: Before bringing new plants into your garden or home, check them for whiteflies and quarantine them if necessary.
Cleanliness: Keep the area around your plants clean. Remove any fallen leaves or debris as these can harbor pests.
Reflective Mulches: In outdoor gardens, using reflective mulches can help deter whiteflies from settling on plants.
Companion Planting: Planting marigolds or nasturtiums near susceptible plants can help deter whiteflies.
Physical Removal: In the early stages of infestation, you can physically remove whiteflies by gently washing them off with water or wiping the leaves with a damp cloth.
Yellow Sticky Traps: These can be used to monitor and reduce whitefly populations. The yellow color attracts whiteflies, and the sticky surface traps them.
Insecticidal Soap or Horticultural Oil: Apply these products according to label instructions. They are effective against whiteflies and are less harmful to beneficial insects.
Neem Oil: Neem oil is a natural insecticide that can help control whiteflies. It disrupts their life cycle and prevents them from feeding and reproducing.
Biological Control: Introduce natural predators like ladybugs, lacewings, or Encarsia formosa (a parasitic wasp) to control whitefly populations.
Chemical Pesticides: If the infestation is severe, chemical pesticides can be used as a last resort. Systemic insecticides are particularly effective against whiteflies. However, be mindful of the impact on beneficial insects and follow the manufacturer's instructions.
Regular Monitoring: Regularly check your plants for early signs of whiteflies, especially on the undersides of leaves.
Avoid Overuse of Nitrogen: High nitrogen levels can attract whiteflies. Use balanced fertilizers to avoid this.
Be Persistent: Whiteflies reproduce quickly, so repeated treatments may be necessary to control an infestation.
Remember, an integrated approach combining several of these methods is often the most effective strategy for preventing and controlling whiteflies.
Ingredients: Mild liquid soap (like dish soap) and water.
Recipe: Mix about 1-2 teaspoons of soap with a liter of water.
Application: Spray the solution directly onto the affected areas of the plant, especially the undersides of leaves where whiteflies congregate. Repeat every few days until the whiteflies are gone.
Ingredients: Neem oil and water.
Recipe: Mix a few milliliters of neem oil with a liter of water. Add a small amount of mild liquid soap to help emulsify the oil.
Application: Spray liberally over the plant, ensuring all surfaces are covered. Neem oil disrupts the life cycle of whiteflies and acts as a repellent.
Ingredients: Garlic cloves, water.
Recipe: Blend a few garlic cloves with two cups of water. Strain the mixture to remove solid bits.
Application: Spray on the plants. Garlic's strong smell can deter many pests, including whiteflies.
Ingredients: White vinegar and water.
Recipe: Mix one part vinegar with three parts water.
Application: Spray carefully on the plants. This can alter the pH on the leaf surface, making it less hospitable to whiteflies.
Ingredients: Rubbing alcohol and water.
Recipe: Mix one part alcohol with one part water.
Application: Spray onto the infested areas. Alcohol can kill whiteflies on contact.
Test First: Always test your homemade spray on a small part of the plant first to ensure it doesn’t cause damage.
Avoid Strong Sunlight: Apply these sprays during cooler parts of the day or when the plant is not in direct sunlight to prevent leaf burn.
Thorough Coverage: Make sure to cover all areas of the plant, especially the undersides of leaves.
Regular Application: For best results, you might need to apply the treatment several times, every few days.
Homemade treatments, while generally safer than chemical pesticides, can still harm some plants, especially if used excessively or in very strong concentrations. Observe your plants' reactions after application. If there's any sign of damage, discontinue use.