How do I get rid of whitefly in the greenhouse?

Question

I get a lot of whitefly in my greenhouse, where I'm growing peppers and tomatoes. What's the best way to get rid of them?

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Answer

Whitefly tend to be a problem in greenhouses, because these tiny white flying insects need warm conditions as they’re right at the northern end of their range. It would be unwise to use an insecticide on peppers and tomatoes as you’re going to eat them. Fortunately there are lots of natural predators and one of the best is the hoverfly. These creatures resemble wasps, but do not sting, and they hover rather than fly due to an unusual wing structure. Most of the adult hoverflies found in British gardens have predatory, maggot-like larvae. The adult lays a single ivory-white, oval egg close to pests. The larva emerges and soon clears up any pests.

Certain plants and colours will attract adult hoverflies into your greenhouse and they love orange and yellow flowers. Single-flowered French marigolds, such as ‘Dainty Marietta’ (from Mr Fothergill’s), should be grown in front of your tomatoes, or you could grow calendulas (pot marigolds).

Keep the greenhouse temperature down by opening doors and windows as much as possible. Open doors and windows also allow wrens in,and wrens are very good at frisking greenhouses and frames.

Make sure that you clear the greenhouse by the end of September, if possible, removing all vegetation. Doing this should break the life-cycle of any aphids and whitefly.

If you spot clusters of eggs in autumn, leave them alone because spiders and many other beneficial insects only lay one batch of eggs – ready for next spring.

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