If your chestnut gets brown spots on the leaves or even the entire leaves turn brown, then it is high time to examine the tree thoroughly. It is probably suffering from pests or disease and should be treated urgently.
What causes brown spots on chestnut leaves and how can I protect them?
Brown spots on chestnut leaves can be caused by sunburn, the horse chestnut leaf miner, or a fungal infection called leaf tan (Guignardia aesculi). To protect the tree, you should collect and dispose of fallen leaves to prevent the spread of pathogens.
Where do the brown spots come from?
The simplest cause of brown spotted leaves is simple sunburn. Even if the chestnut likes a sunny location, it can suffer from too much sun, especially if the sunshine leads to prolonged drought.
Brown spots on the leaves of your chestnut tree can be caused by the horse chestnut leaf miner, or its larvae. These eat tunnels, so-called mines, in the leaves. This interrupts the supply of water and nutrients and causes the leaves to wilt prematurely. Although the affected chestnut does not die, it is significantly weakened. This means the harvest is smaller and the chestnut is more susceptible to other diseases and pests.
Leaf browning also causes the leaves of a chestnut to discolor. This is caused by a fungal infection. Guignardia aesculi is responsible. The spots can be several centimeters in size and are reddish brown with a light yellow edge. If the infestation is severe, the wilted leaves curl up, which has given the disease the name “leaf rolling disease”.
Possible causes of brown spots:
- Horse chestnut leaf miner
- Sunburn
- Leaf browning (fungal infection with Guignardia aesculi)
How can I save my chestnut?
You can only help your chestnut a little this year. But preventing and containing the disease for the next year is possible and strongly recommended. This is the only way you can protect your chestnut in the long term.
To do this, collect the fallen leaves before the larvae of the horse chestnut leaf miner can retreat into the ground or the fungal spores of Guignardia aesculi spread in the ground. Dispose of the leaves reliably; it is best to burn them. The pathogens can also survive in compost if it does not reach at least 60 °C core temperature.
Tip
Infected leaves do not belong in the compost. Both the larvae of the horse chestnut leaf miner and the spores of Guignardia aesculi could survive there and infest other trees.
