Beet leaf miner

Beet leaf miners are flies whose maggots tunnel inside the leaves of beetroot, spinach beet, Swiss chard and some other related plants creating large irregular blotch-shaped mines.

Beet leaf miner damage

Quick facts

Common name Beet leaf miner
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?

Beet leaf miners are a type of fly and the adults resemble small house flies. It is the larvae that cause the damage by tunnelling into leaves of susceptible plants and eating the internal tissues.

Symptoms

Beet leaf miner maggots tunnel inside leaves creating large irregular blotch-shaped mines. The damaged areas may be pale green initially but mined parts of the leaf soon turn brown and shrivel. Early summer damage is potentially the most harmful to the plants as crops will be set back more than infestations of more mature plants.

Control

Non-chemical control

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 attempt to control infestations by removing mined leaves or squeezing the mined areas to crush the maggots. Early summer damage is potentially the most harmful to the plants.

Chemical control

There are no pesticides available to home gardeners that are likely to give good control of beet leaf miner.

Biology

The beet leaf miner has two or three generations between April and September. The females, which resemble small house flies, lay small batches of eggs on the foliage of beetroot, spinach beet and Swiss chard. Larvae feed on internal leaf material and the fully grown larvae go into the soil where they spend the winter as pupae.

Advertise here

Gardeners' calendar

Advice from the RHS

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Discuss this

for the site or to share your experiences on this topic and seek advice from our community of gardeners.