Whitefly on the underside of leaves

Whitefly

BBC Gardeners' World Magazine

Published: Sunday, 24 March 2019 at 3:00 pm

Discover organic methods to protect your greenhouse plants from whitefly.

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Turn over a leaf and you'll see 2mm long white flies. With a life cycle of just three weeks, whitefly breed very fast. Both adults and offspring are sap feeders and a severe attack will weaken a plant. They excrete the sticky excess, called honeydew, onto lower leaves where it encourages black sooty mould to grow. If left, this weakens the growth of the plant.

Symptoms

When you brush past your plants in the greenhouse clouds of tiny white flies fill the air.

Find it on

tomatoes, cucumbers, fuchsias, other greenhouse plants

Organic

Hang up yellow sticky traps to catch flying adults. Grow strong-smelling plants, such as French marigolds, alongside your tomatoes as a deterent. Every two to three days spray the underside of leaves with a soap-based spray containing fatty acids to kill emerging adults. When the temperature remains above 10 celsius in the greenhouse you can use a biological control, such as the parasitic wasp, Encarsia formosa, which attacks the juvenile forms of whitefly.

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