Allium Leaf Miner
Allium Leaf Miner, Onion Leaf Miner
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The Allium Leaf Miner is a tiny leaf-mining fly, that looks similar to an average housefly. As the name suggests, they're severe pests of Alliums; they're widespread across mainland Europe and the UK. Allium Leaf Miner damage plants by tunnelling through leaves, eating the internal tissue as they move around the foliage. The leaf mines created by an Allium Leaf Miner look like yellow meandering lines, which typically span across the whole leaf. The mines are often accompanied by yellow/white dots, which indicates a female fly has deposited eggs. Other symptoms to look out for include twisted onion leaves and stunted growth in Alliums. Infested leeks become susceptible to secondary bacterial rots.
Leaf mining insects can cause considerable damage to crops from their intrusive way of feeding.
Adults: Small, brown-black flies (3mm) that look a lot like normal house flies. Larvae: The larvae look like small, white, headless maggots. Pupae: Brown, ovular in shape (3mm), located in the within the stems and bulbs of the plant. Leek moths can create similar symptoms in onion plants. The way to distinguish these two insects is by the larvae. Leek moth caterpillars are creamy white, unlike Allium grubs which are white. Leek moth caterpillars possess legs and black heads, both of which are absent in Allium grubs.
Distinctive trail of yellow/white dots on Allium leaves. White/yellow lines (mines) on foliage of plant. Brown, oval shaped pupae found within the bulbs and stems. Stunted growth Dried out or twisted leaves. Secondary rots
Widespread across Europe
Protect plants with an insect-proof mesh during periods where females are active (March-May and September - November). Rotate crops each year so that when adult females emerge it will be more difficult for them to locate an appropriate host plant. Avoid periods of flight activity by planting Allium later in the year, such as the end of May. Utilise plant companion plants to deter leaf-mining activity. Beets, carrot, celery, lettuce and cabbage have been suggested as useful companion plants for the onion family. It is thought Allium leaf miners dislike the scent of mint, lemon balm and common rue.
There are currently no chemical treatments available for home gardeners for this type of plant.