Hellebore Leaf Miner
Hellebore Leaf Miner
The Hellebore Leaf Miner is a tiny fly, belonging to the taxonomic group that holds flies with leaf-mining larvae. Leaf-mining insects are usually small, and it's the larvae that cause the most the damage. They do this by tunnelling through the leaf tissue, eating the contents as they do. Mining activity can be a helpful clue to help you identify what's eating your plants. As well, the species of plant infested can be a telltale sign. For example, these miners will only infest Helleborus foetidus. Dull brown blotches paired with sinuous light brown trails should be evident across foliage.
Leaf mining insects can cause considerable damage to foliage from their intrusive way of feeding.
These flies are a food resource for birds and predatory insects.
With leaf-mining insects, identification is normally best achieved from the species of the plant infested and characteristics of the mines. For this fly, it's possible to have several mines on one leaf. Mines are typically black and brown, appearing as blotches on leaves. The mine starts off narrow, slowly widening until eventually becoming a large blotch. Long black streaks of excrement may be evident within the mines. Fly larvae are tiny legless maggots. Larvae will pupate within the leaf mines. The larval skin hardens, forming a cocoon-like structure (puparium). It's possible to see these if you hold a mined leaf up to the light. They will appear like little black dots in the mines of leaves.
Females will leave numerous pale spots as a result of her feeding, which will be dotted about the plants' foliage. Mines matching the above description, discolouration, and dried up leaves is a good indication that your plant has been infested with this leaf-mining insect.
This species is a new resident in the UK. These flies are present throughout mainland Europe.
Unfortunately, there's no effective means of controlling this pest biologically. It's suggested to monitor plants regularly, removing leaves as they become infested.
There are currently no chemical treatments available for home gardeners for this type of plant. H. foetidus can tolerate infestations of this insect. Heavily infested plants should be checked regularly, pruned and destroyed accordingly.