Leaf miners are the most dangerous pests that can plague a thuja. If a severe infestation of the hedge is not treated immediately, it can result in the tree of life dying completely. How to recognize and combat a leaf miner infestation on your Thuja.
How do you recognize a leaf miner infestation on Thuja?
A leaf miner infestation on Thuja can be recognized by the following signs: discolored or brown shoot tips, hollowed out tips, black dots of droppings and small caterpillars in the tunnels. If infested, immediately cut off affected shoots and dispose of them with household waste.
Leaf leaf miner causes lasting damage to thuja
There are two leaf miners that attack the tree of life: Thuja leaf miner (Argyresthia thuiella) and Juniper leaf leaf miner (Argyresthia trifasciata). Both are closely related, but differ in that the butterflies fly and lay their eggs at different times.
The juniper leafminer has white-grey mottled wings and flies from May to June, the thuja leafminer has brown wings and appears from June to July.
Identifying thuja leaf leaf miner infestation
Any discoloration of the tips of the Thuja shoots should attract your attention. If the tips turn brown, examine them closely. The following signs indicate a leaf miner infestation:
- translucent or brown tips
- Tips are hollow inside
- black poop dots
- there are small caterpillars in the corridors
First measures to combat the pest
If your thuja is infected with leaf miners, you must take immediate action, especially if an entire hedge is affected. Cut off all infected shoots and dispose of them in household waste - not in compost! You can also burn them.
If there is a severe infestation, the pruning must be very vigorous, but must not go all the way into the old wood.
The use of sprays is only necessary if the occurrence is very severe. For the control to be successful, spray once in June or July to catch the moths directly. A second treatment occurs when the caterpillars have hatched.
What remedies are there against leaf miners?
The trade has a number of products available to combat leaf miners (€8.00 at Amazon). Even products that are not dangerous for bees must be used sparingly as they pollute the environment.
An ecological control is possible with nettle manure. To do this, you need to put a kilo of fresh nettles (without flowers!) in a barrel with ten liters of water for at least two weeks. The brew can then be sprayed directly and undiluted.
However, you should not underestimate the odor nuisance for the neighbors.
Tip
Thuja shoot death can also be caused by fungal infestation. The shoots also turn brown, but unlike a pest infestation, they are not hollowed out.
