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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 miners are a type of fly, the adults resemble small house flies. The larvae cause plant damage by tunnelling into leaves of susceptible plants and eating the internal tissues.
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 may be set back, infestations of more mature plants may have less impact although may render leafy crops inedible.
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.
There are no pesticides available to home gardeners that are likely to give good control of beet leaf miner.
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.
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