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How to control Whitefly
Whitefly – Identification and Control
Whiteflies are tiny white, cream or silvery pests with two pale wings on their backs, commonly found on vegetable and ornamental plants. You can often tell where they have been feeding as they leave behind a whitish, powdery wax. Like aphids, whiteflies suck sap from plants and excrete a sweet honeydew, which can cause mould to form on the leaves. Whiteflies lay oval-shaped eggs vertically on the underside of leaves, which can be difficult to see. These eggs hatch up to 23 days later into wingless nymphs that continue feeding and causing damage.
Symptoms
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Leaves turning yellow, appearing dry or falling off
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Reduced plant growth leading to poor yields
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Sticky honeydew on leaves which can attract ants and cause mould
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Heavy infestations can significantly weaken plants
Control
Whiteflies are one of the more difficult pests to eradicate without pesticides, so prevention is the most important step. Place sticky traps around your garden to help catch the adult flies and monitor population levels. Remove any infected leaves and dispose of them in a sealed plastic bag away from the garden.
When whiteflies are in their nymph stage, an insecticidal soap can be sprayed directly onto the affected areas, or a gentle hose can be used to wash them off the leaves. Adult whiteflies need to be directly hit by the spray for it to be effective, so spraying early in the morning is best, as this is when they are least active. Biological controls are available online and work well in greenhouses, although they are not usually effective outdoors.
Tips
Keeping your plants healthy and well-watered will make them less vulnerable to whitefly infestations. Avoid overcrowding plants to improve air circulation, as stagnant air encourages pests. Regularly check the undersides of leaves for eggs or nymphs so infestations can be dealt with early. Using reflective surfaces such as aluminium foil or reflective mulches beneath plants can help deter whiteflies, as they dislike bright reflected light. Encouraging natural predators such as ladybirds and lacewings, particularly in greenhouses, can also help keep populations under control.