All information about the annoying pests

the essentials in brief

• the Leaf miner is a tiny, inconspicuous butterfly.
• It lives mainly in deciduous trees and its caterpillars eat their way through the leaves.
• These turn brown and eventually fall off.
• Leaf miners are fought with scissors and pesticides as well as preventive measures.

What are leaf miners?

Leaf miners are very small, quite inconspicuous butterflies that have only appeared in Europe since the 1970s. In particular the thuja leaf miner - one of the approx. 230 European species - feared by hedge owners since the 1990s because of their invasive nature. The different species are mostly specialized in certain host plants, after which they are named. The moths live in trees and other woody plants, and their caterpillars in particular cause great damage. The animals live as so-called miners, i. H. they mainly eat their way through the leaves of the plants and thus damage them.

This is what the pest looks like

The external appearance of leaf miners and their caterpillars differs depending on the species. However, all varieties have certain characteristics in common:

• very small moths with a narrow wingspan of between five and nine millimeters
• only rarely slightly larger
• mostly flesh to olive colored body
• other colors are also possible
• fringed wings
• pronounced proboscis
• Caterpillars are noticeably flat and, depending on their age, up to approx. 5 millimeters long
• Appearance of the caterpillars strongly depends on the respective larval stage

Knowledge of the way of life is important for efficient control

Most leaf miner species are active very early in the year and fly from around April. The pests overwinter as caterpillars or even adult moths in the fallen or Leaves remaining on the tree can also be found in the Tree bark hide. The females lay up to 40 eggs, from which the larvae hatch within just two to three weeks. These immediately begin their work of destruction and drill into the inside of the leaves in order to eat ducts in the tissue there. After a total of five larval stages, the caterpillars pupate in these tunnels, mostly even with bare ones eye can be seen.

The pupae of the leaf miners are easy to recognize

Depending on the type and weather, up to four generations of leaf miners develop each year, and they are not limited to just one tree. On the contrary: If it is warm and dry, all neighboring trees are also infested in no time due to the rapid development. For this reason, it is important to act as early as possible in the event of a suspected infestation. This is the only way to prevent the plague from spreading. Are you or There has been a history of leaf miners in your neighborhood, you should take appropriate precautionary measures. Above all, this includes always clearing away and disposing of autumn leaves.

Digression

This butterfly damages chestnut

Damage - How to recognize a leaf miner infestation

Infested plants typically turn brown quickly from leaf miner infestation. You can find out what causes thuja to turn brown in the following video.

The damage caused by the eating activities of the caterpillars can be seen very quickly due to the fact that they often occur in large numbers. However, the majority of the damage is only visual: the infected tree looks ugly, but is not directly endangered. Trees damaged by leaf miners rarely die, as the butterflies prefer to populate larger and therefore more resilient specimens. Typically, the damage is shown by:

• an unsightly brown coloration of the leaves or needles even in early summer
• mostly deciduous trees are affected, but some conifers (thuja) are also endangered
• this is often followed by early leaf fall
• heavily infested trees often limit their growth
• Decrease in flower formation (v. a. with lilac) or Formation of fruits (chestnut)

In some cases, trees infested with leaf miners often begin to bloom again in late summer or even autumn - namely when the tree has recovered from the infestation. In the case of deciduous trees, new, healthy leaves form in the following spring. Only conifers such as the thuja look permanently ugly, as the brown needles do not turn green again even after successfully combating the pest.

These plants are particularly often attacked by leaf miners

Maple leaves taste particularly good

The thuja (trees of life) and horse chestnuts, which are so popular for dense hedges, are particularly often attacked by the voracious leaf miners. However, these tree species are also endangered:

• Maple (acer)
• Robinia resp. Mock acacia (Robinia pseudoacacia)
• Azaleas (Rhododendron molle and other species)
• Lilac (syringa)

It also shows that the pests are increasingly conquering other host plants. Apparently, the moths are not fully specialized, but can expand their range of prey. You should therefore pay particular attention to a possible infestation in stone and pome fruit trees and generally in deciduous trees. This is especially true if other trees - such as the thuja hedge - are already infested in your garden.

Fight leaf miners

Infested leaves should be disposed of

Unfortunately leaf miners are difficult to control once you have the infestation on the tree. Therefore, preventive measures are all the more important, especially collecting the fallen leaves - this way you prevent another plague in the following year.

Pheromone traps

Pheromones are specific sexual attractants that female leaf miners use to attract males to mate. Special pheromone traps are available in stores, which you hang in the trees and which then trap the male moths. The animals get stuck on the glue attached in the trap and can no longer escape. Attractant traps reduce the infestation pressure, as fewer male moths are also fewer fertilized females, which means fewer caterpillars, are not, however, suitable for sole use Combat. With their help, however, you can determine whether there is a leaf miner infestation at all and how strong it is. After that, you'd better take effective countermeasures.

Spraying with nettle manure

Spraying with nettle manure has also been shown to be effective against the leaf miner, but not in the case of an acute infestation. Inject endangered woody plants regularly as a preventive measure, which you should start as early as April at the latest and should continue until late autumn. The method is therefore quite time-consuming and difficult to carry out with large trees - such a horse chestnut can grow up to 30 meters high. In the case of smaller trees and shrubs, such as thujas, lilacs or rhododendrons, however, spraying is practicable.

Nettle manure is a cheap, environmentally friendly way to control the leaf miner

How to prepare the nettle manure:

1. Collect a kilogram of nettles.
2. If possible, these should not bloom.
3. Otherwise you can use the whole plant including leaves and stems.
4. Chop up the herb as it will dissolve the active ingredients better.
5. Put the plant material in a plastic bucket.
6. Do not use a metal container, this will lead to undesirable chemical reactions.
7. Pour ten liters of rainwater on it.
8. Add a handful Rock flour(€ 12.33 at Amazon *) (against the unpleasant smell that develops later).
9. Put the bucket in the Penumbra.
10. Cover it with a mosquito net, beach mat, etc. ä.
11. After about eight to ten days, the liquid manure is ready and can be used.

Spray the trees every two weeks between March / April and September / October. When filled in canisters, the finished liquid manure lasts for about a year.

Spray with neem

Also a spray with the natural insecticide neem (or neem), one from the Indian neem tree (azadirachta indica), shows anti-feeding effect on the caterpillars of the leaf miner and damages them in their Development. However, neem products are quite expensive, which is why regular treatment of a large tree in none reasonable cost-benefit ratio - especially since neem also affects other insects Has. In this case, similar to the stinging nettle manure produced in-house, it is primarily used for smaller trees.

Digression

Are there approved pesticides against leaf miners for home and hobby gardens?

Regular pruning

Regular pruning protects the thuja from leaf miner infestation

Together with a spray, regular pruning, especially of threatened thuja hedges, is an effective prevention against leaf miner infestation. You should proceed as follows:

• Cut back thuja in early spring
• at the same time as the spraying (e.g. B. with nettle manure)
• prune again in July
• at the same time further spraying with nettle manure

Under no circumstances should you dispose of the clippings on the compost, but rather in the household waste. burn it up.

Collect and dispose of autumn leaves

Another very effective remedy against annoying leaf miners is this: the careful collection and disposal of fallen leaves, especially autumn leaves. Be very consistent in this regard so that no leaflet is left lying around and the animals that hibernate in them can possibly cause another plague in the following year. Under no circumstances should you dispose of the leaves on the compost, as the moths develop here and will still hatch next spring. Instead, throw the leaves in the trash or, better yet, burn them. The latter is of course only possible if the burning of garden waste is allowed in your residential area. This method is particularly useful for infected horse chestnuts and other large deciduous trees.

Establish predators

Birds like leaf miners to eat

Like so many other pests, the leaf miner also has natural enemies that literally like to eat the butterfly and thus decimate the population without any further action on your part. Most notably, this includes some songbirds such as titmice, which you will find in endangered with some Tree-hung nesting boxes and strategically placed feeding places can attract you into your garden. Please note that the feathered pests will only feel comfortable with you if you make your garden bird-friendly:

• no use of chemical pesticides (especially no insecticides!)
• these destroy the basic food of the birds and also poison them at the same time
• a dense population of trees and other woody plants, if possible native species
• dense hedges, ideal for breeding
• Feeding places, not only in winter
• several nest boxes

Besides birds are too Parasitic wasps(€ 69.90 at Amazon *) natural antagonists of leaf miners. You can buy these - completely harmless - beneficial insects in specialist shops and settle them specifically in endangered trees. The advantage of such a measure is that Parasitic wasps are effective against a whole range of other garden pests.

Further measures

Since leaf miners often hide in the tree bark during the winter months, you should surround or use rings of glue around the trunks of endangered trees. Brush with a mixture of wallpaper paste and lime in early autumn. In this way, the animals cannot retreat into the bark, which means that another place of retreat remains blocked.

frequently asked Questions

In which season are leaf miners particularly active?

Leaf miners are mainly active two times a year, so you should base your control strategy (spraying and pruning) on ​​them. The main peaks of moth activity are in early spring, mostly in April, and again in July / August. But even in the meantime, if the weather is suitable, further generations can fly out, which is why regular spraying with biological agents is so important.

What to do if there are leaf miners in the apartment

In rare cases, such as when an infected tree is near a window, leaf miners can also enter the house or get into the apartment and wreak havoc on the indoor plants. Therefore keep doors and windows closed or put an insect screen on them as soon as you suspect an infestation. To foods such as flour etc. The leaf miners do not go, however, as this does not correspond to their natural diet. If you find moths in your supplies, they are definitely so-called Flour moths (Ephestia kuehniella), which look very similar to the leaf miners outwardly.