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Can companion planting reduce allium leaf miner?

Each year we organise several citizen science experiments that our members can participate in to help inform the way we grow organically. This experiment - to look at the benefits of companion planting as a pest deterrent - is taking place in spring/summer 2024.

How to take part 🔗

We would like to see if we can reduce the incidence of allium leaf miner in leeks by planting companion plants between them. We will test the effects of growing two contrasting shaped types of plant amongst leeks to see if it will work as a way of managing allium leaf miner.

This will improve our understanding and may give gardeners new options for organic pest control.

Sign up Deadline 🔗

Background 🔗

Allium leaf miner (Phytomyza gymnostoma) was first discovered in the Midlands in 2002 and has steadily spread throughout the UK. The pest causes extensive damage to alliums especially in leeks. Currently, the only organic method of controlling the pest is to cover the crop with fine mesh. As this is unsightly and adds to the amount of plastic used in gardens and allotments, gardeners would welcome alternatives.

There has been extensive work to show that crops grown amongst other plants are attacked less frequently by pests. It is thought that this is because the companion plants disrupt pest attack by reducing the chance of the pest landing on a crop plant leaf. Surprisingly, unscented plants were just as effective as scented plants. You can read more about this work here.

The size and shape of the companion plants is also thought to be important. Much of this work has been done on brassica pests, and there has been little or no work to see if such approaches could deter allium leaf miner. We would like to test the effects of growing two contrasting shaped types of plant amongst leeks to see if it will work as a way of managing leaf miner.

You will grow a control plot of leeks alone, one plot with leeks mixed with low growing plants (white clover) and one plot with leeks mixed with tall plants (chard) and monitor whether they get attacked by allium leaf miner. This will improve our understanding and may give gardeners new options for pest control.

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Allium leaf miner has become more prevalent in communities over the past few years
Information
Difficulty Medium – some familiarity with growing leeks would be an advantage
Timescale March - December 2024
Space required 3 x 1 m2 plots (preferably with a small gap between each)
Materials needed Small seed trays and compost
Commitment Time to grow and look after leeks and companion plants, 20 minutes monthly monitoring of pests