If the leaf miner attacks the thuja, it will turn brown and die. We will show you how to fight the pest and save the thuja.
If you let your gaze wander through the neighboring gardens, you will surely notice one thing: thujas can be found everywhere. And that's not even surprising, because thujas make perfect hedge plants. Lined up closely together, they can grow into a stately hedge in just a few years. So they offer a quick and opaque privacy screen, which is also easy to care for and inexpensive. So it doesn't matter if a plant dies.
But it's bad if all of a sudden all the thujas, as the thujas are also called, get brown tips and look sickly. Then at the latest it is time that you take a closer look at the plants. If the tips turn brown over time, then this is a clear indication that something is wrong here.
Several thujas are usually affected
It happens all too often that thujas suddenly turn brown and die off in a very short time. Of course, this is particularly annoying within a hedge. And it is precisely there that it is not just a matter of one plant, here several are often affected. One culprit is usually responsible for the death of the plants: the leaf miner. To be precise, this is the Thuja leaf miner.
Damage:
The thuja leaf miner is a small butterfly that belongs to the spider moth family. And this is exactly what lays its eggs on the leaf scales in June/July. The caterpillars that hatch from them then eat their way through the shoot tips and literally hollow them out. The result: the infested scales on the thuja branches first turn yellow from the tip and then brown to gray over time.
Meanwhile, the caterpillars that overwinter in the shoots pupate. The new moth generation then hatches in June/July. Just like the previous generation, they again lay eggs on the scaly shoots of the thuja. So the whole game starts over again.
Control measures:
» pruning:
If you have an infestation with thenotice the miner moth, then quick action is important to save your trees of life. In the case of a light infestation, it is advisable to cut the shoot tips in spring and thus before the moths hatch. In this way you can contain the spread of the pest.
In the case of a severe infestation, however, you have to cut off a lot more. Here even a drastic pruning of the shoots is necessary. But don't worry, your thuja will sprout splendidly afterwards.
Important:
You should not dispose of the affected branches with the compost, but with the household waste. You can also burn the clippings. This is how you prevent the pests from spreading.
» Pesticide:
It is also advisable to spray an insecticide against the leaf miner. This remedy should then on the one hand prevent egg laying and on the other hand prevent the newly hatched caterpillars from penetrating the shoots. It is therefore always advisable to inject twice. Once in early June to meet the moths and once when the caterpillars have hatched. A recommended insecticide for combating leaf miners is, for example, COMPO Triathlon Universal Insect-free AF with active ingredients from nature.
If you prefer to use natural pesticides, you can also spray your thujas regularly with nettle manure. To do this, fill a tub with 1 kilogram of nettles and 10 liters of water, close it and leave it in the sun for 14 days. However, stirring regularly is important. You can then use the liquid manure directly.