• The fly can be largely avoided by raising
  A seedling is a young plant grown from seed.

  seedlings in seed trays or pots and planted out once they have germinated
• As the fly only affects young seedlings encouraging rapid healthy growth soon after
  Germination is the process by which a seed develops into a new plant. It starts with the seed coat absorbing water, expanding and splitting, which allows oxygen and water into the seed so its food reserves can be broken down and used by the embryo for growth. The first root (called the radicle) pushes into the soil to anchor the new plant in place and start absorbing water and nutrients. The first shoot (called the plumule) then grows upwards, out of the soil, towards the light.

  germination is key to limiting problems caused by this insect
• Adult flies are attracted to soil containing fresh compost, so dig in organic matter the previous autumn where beans are going to be grown
• The soil should be well prepared in order to encourage rapid germination
• Garden-sown beans can be protected by insect barrier netting, horticultural
  A soft, fibrous, translucent material laid over or around plants hastening their growth and protecting them against weather and pests. Heavier grades of fleece give about 2°C of protection from frost. It is usually used without supporting hoops.

  fleece is especially valuable as it provides extra warmth that is highly beneficial to tender crops as well as excluding bean seed fly
• Encourage predators and other natural enemies in the garden such as birds, hedgehogs and ground beetles. Some ground and rove beetles are efficient predators of root feeding maggots 
• A mixture of pathogenic nematodes, sold as Fruit and Vegetable Protection, can be watered into the soil which may control the young larvae, this is available by mail order from biological control suppliers. Nematodes should be used in a targeted way as they can also affect non-target species

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Biological control suppliers (pdf document)

There are three to five generations of bean seed fly during the spring and summer but it is the first generation in May, that is often the most damaging.

Adult bean seed flies are 6 mm long and resemble house flies. They become active from May onwards and deposit eggs in the soil. The eggs hatch within a few days. The larvae are white, legless and headless maggots that reach 8 mm long. They feed on the seeds and roots of beans and sometimes other plants such as brassicas, cucurbits, lettuce, onion and sunflower. They can kill young seedlings. The larval stage lasts one to three weeks before they pupate. New adults emerge after three weeks. The flies can overwinter as pupae in the soil, emerging the following year in early spring.