Ornamental plants and vegetables
White lines on the leaves? This little fly is behind it
Typical signs of leaf miner infestation are small, white lines in the leaves
© Tomasz Klejdysz/Getty Images
If you see fine white lines on the leaves of your ornamental or crop plants, a tiny pest has got to work: the leaf miner fly. It not only feeds on the plant sap, but also lays its eggs in it. How the infestation affects your plants and what you can do about it.
It is only a few millimeters in size and can still cause great damage: the leaf miner becomes active in the warm summer months – and targets the fresh foliage of ornamental plants and vegetables. To be more precise, it is the juice that the small pest drinks after it has pierced the plant of its choice. However, this does not create the spiral-shaped tunnels on the leaves that are an important indicator of infestation. The actual damage is caused by the larvae of the leaf miner, which lay their eggs in the puncture site. To prevent the infected leaves (or in the worst case even the entire plant) from dying, you should intervene in time. We will show you what you can do.
These signs indicate an infestation
A single leaf miner can lay up to 400 eggs during its entire life cycle. Just a few days later, these in turn produce up to 400 larvae that eat their way through the foliage. This creates the typical “mines” – also known as mining tunnels. The special thing about this technique is that the outer skin of the leaves is not damaged. For this reason, the white lines are a typical sign of infestation. In fact, there is already an indication that a leaf miner is attacking your plants: tiny feeding holes that later expand into small tunnels. And cause the affected leaves to dry out and fall off, thus reducing plant growth. In addition, dangerous bacteria and fungi have an easy time at the puncture sites, causing even more damage to the plants. This makes it all the more important to stop the infestation as quickly as possible.
So small and yet so harmful to crops and ornamental plants: the leaf miner
© ViniSouza128 / Getty Images
Stop leaf miner flies? This is what you can do
If your ornamental plants or vegetable patch have been attacked by leaf miners, you can resort to biological control agents that – and this is crucial – are not dangerous to bees: for example, the “COMPO BIO Insect-free Neem” for all indoor, balcony and garden plants. Or you can rely on so-called beneficial organisms that will kill the pest in a natural way: parasitic wasps (only these two species: Dacnusa sibirica or Diglyphus isaea) lay their eggs in the larvae of the leaf miner fly, so that their offspring can eat the fly larvae after they hatch. If there are no more larvae, the parasitic wasps disappear on their own.
A notice: Parasitic wasps are more suitable for home use or closed greenhouses, as they are difficult to control outdoors. If the infestation in the garden is still fresh, it is possible to collect the diseased leaves and dispose of them in the household waste (not on the compost!).
Tip: How to prevent leaf miners
To prevent leaf miners from attacking your crops or ornamental plants, you can take preventive measures – for example, by using Yellow boardsThese are special glue boards to which the (adult) pests stick. This does not completely prevent an infestation, but at least you will notice immediately when leaf miners are trying to feed on your plants.
However, this method is less effective outdoors than indoors, as other insects can also stick to the yellow boards. In this case, it is advisable to cover the vegetable plants with fine-meshed Crop protection nets from an attack by the leaf miner. The advantage of this is that other insects such as aphids or flea beetles, which could normally harm your beneficial insects, are also kept away from your beds.
Another way to prevent leaf miners is to make nettle manure. The smell is said to have a deterrent effect on the sucking insects – but there is no scientific evidence for this. However, since the ingredients also work well against other pests and the manure promotes plant growth as a natural fertilizer, you can’t go wrong by using it.
Sources: Utopia, My beautiful garden, Chamber of Agriculture
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