Beet leaf miner
Beet leaf miner is a fly whose larvae tunnel inside the leaves of beetroot, spinach beet, Swiss chard and some other related plants creating large irregular blotch-shaped mines.
Scientific name Pegomya hyoscyami
Plants affected Beetroot, spinach beet, and Swiss chard
Main symptoms Blotchy leaf mines (pale areas) on leaves
Most active April to September
What is beet leaf miner?
The fly belongs to the family Anthomyidae, it is a diverse group of flies with over 100 species Britain. Whilst a few are leaf miners others feed on roots such as the cabbage root fly. Most do not damage garden plants. More information on this fly family is available from the Anthomyidae recording scheme.
Nearly 900 other insects, including some beetles, sawflies and moths create leaf mines as larvae more information about some for these insects can be found at The leaf and stem mines of British flies and other insects
Leaf miners can be part of a healthy balanced garden, most species will have natural enemies including parasitoid wasps. Birds such as blue tits can sometimes open mines to consume the larvae within. On plants where leaves are to be consumed leaf miners can however, be difficult to tolerate.
Growing susceptible plants under insect barrier netting will prevent female flies laying eggs on the foliage. However, crop rotation must be practised otherwise adult flies may emerge from overwintered pupae in the soil and be trapped under the netting.
On uncovered plants removing mined leaves or squeezing the mined areas to crush the maggots may give some control. A careful search may also reveal the white eggs which are laid in small groups on the underside of leaves. Early summer damage is potentially the most harmful to the plants.
There are no pesticides available to home gardeners that are likely to give good control of beet leaf miner. Pesticide control can have undesirable side effects as it will kil natural enemies and other non-target animals.
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