Chestnuts, whether horse chestnut or sweet chestnut, are quite sensitive trees. It is all the more important to identify and combat diseases and pests at an early stage.
Chestnut trees (Castanea) are imposing and of great natural beauty. Chestnuts are often found in beer gardens, parks and public meadows due to their size, their wonderfully colored flowers and their suitability as excellent shade providers. The chestnut, on the other hand, is only suitable to a limited extent for domestic gardens, as it reaches a height of up to 35 meters, which does not want to fit into a small garden or even a front yard. Since the chestnut is a shallow root, it should not be planted too close to the house, garage or road. The crown also needs some space, so chestnuts do not tolerate competition from other trees in their immediate vicinity. And yet, if you have a plot of sufficient size, it is worth thinking about planting a chestnut - the shade in the summer, the brown fruits in the fall with which you can do crafts and decorative items, and the rich colors of the flowers in the spring will you sure to quickly convince you of the benefits of this tree.
However, like any cultivated plant, the chestnut also requires a certain amount of care and good protection against diseases and pests. For example, when you prune the chestnut, it is important that you follow the necessary precautions and instructions to prevent disease or pests from invading the cuts.
Chestnut facts and figures
The chestnut originally comes from the southern Mediterranean area and the Balkan Peninsula, but was also native to Central Europe as early as the Middle Ages. There are two species, the horse chestnut and the sweet chestnut, each of which has over 100 subspecies. The chestnut can grow up to 35 meters high - even smaller subspecies usually reach a height of at least 10 meters. Horse chestnut trees can even be several hundred years old and reach a trunk diameter of more than 1 meter. As a deciduous tree, the chestnut provides plenty of shade in summer.The flowers of the chestnut are white or red - in crosses between the species you can also marvel at different shades of pink.
Despite their size and grandeur, chestnut trees are very susceptible to diseases and pests if not handled properly.
Overview of the most common pests
Chestnuts that are infested with pests are often severely weakened as the infestation progresses. Trees of all ages can be affected. If you notice that pests are at work on your chestnut, you should react as soon as possible. Although there is not necessarily a risk of the tree dying off immediately or quickly, the chestnut loses a lot of its elegance due to the pest infestation and gradually the weakening of the tree is also noticeable in the lack of stability. Here is an overview of the most dangerous pests for chestnut trees:
❍ The horse chestnut leaf miner:
The white horse chestnut in particular suffers greatly from the leaf miner, a small species of butterfly with a feathery hindquarters and measuring barely half a centimeter in size. The first signs are brownish discoloration on the leaves of the chestnut immediately after flowering. These are caused by the young larva of the leaf miner. This pest infestation first appeared in Austria in 1989 - since then the moths have been spreading throughout Europe. On average, around 100 kilometers a year in each direction.
Some time after the tree was first infested, large parts of the foliage are brown and the leaves fall off much too early. As a result, the chestnut no longer has the opportunity to carry out the photosynthesis that is vital for the tree via the green foliage - the chestnut is considerably weakened, which can even lead to the death of the entire tree in the event of a long-lasting infestation. A sign of a particularly strong weakening of the tree is a second bloom, which then begins in August or September. The greatly weakened tree loses a lot of strength as a result.
➔ Combat:
There are some means to combat chestnut leaf miners - but none of these means are approved in Germany. The chemical agents in the insecticides that are really suitable for eliminating the leaf miner are too aggressive and the damage to the rest of the environment is too severe. And yet you can do something about the leaf miner. If your tree is infested in the first year, be sure to collect and burn the fallen leaves immediately to keep the larvae outsurvive.
By the way, all kinds of birds are natural enemies of leaf miners. So make your garden interesting for birds - the more birds stay in your garden and look for food, the greater the chance that the leaf miner will be in your garden next year garden is absent. Here is a reading tip: Attracting birds - this is how you get atmospheric chirping in the garden.
❍ The chestnut borer:
The chestnut borer is a weevil whose females lay larvae on the fruit of the chestnut. About 40 eggs are laid - one egg on each fruit. The larvae then feed inward, wait for the chestnut to fall off, and then feed back out where they burrow into the ground and hibernate.
➔ Combat:
The chestnut borer can cause major damage to the fruit stock and even destroy more than half of all fruit on the tree if the infestation is sufficiently severe. In order to avoid a growing infestation in the following years, you should definitely collect the fruit of your sweet chestnut immediately after it falls and destroy the affected fruit so that the larvae do not remain in your garden and more female sweet chestnut borers attack your tree in the following year.
❍ The early chestnut moth:
The early chestnut moth is a butterfly. It lays its eggs on the leaves. After hatching, the larvae attack the fruit. They pierce through the pericarp and eat the fruit. Then it's on to the next fruit. In order to get from fruit to fruit, they pull silky threads which they then climb along. The infestation can be recognized quickly by these threads, but also by the empty fruit husks that fall down early. It becomes particularly problematic when the early chestnut moth, which, like the sweet chestnut borer, mainly affects sweet chestnuts, pupates. Because this process takes place under the bark and again leads to great damage to the stock. The more early chestnut moths infest a tree, the greater the damage caused by pupation.
➔ Combat:
Light, pheromone and fruit juice traps have proven to be good antidotes. There are some chemical agents against the early chestnut moths, but here too the use of these is not permitted in Germany. Lighter chemical insecticides can work, but the chances are relatively small.
❍ The late chestnut moth:
The late oneChestnut moth bears a close resemblance to its early namesake. However, the larvae overwinter here in the ground and thus cause less damage to the tree itself. They are more of a threat to the fruit stock of the sweet chestnut and can greatly reduce the harvest. There are hardly any obvious signs of an infestation, only the empty fruit husks that fall from the tree much too early can serve as an indication.
➔ Combat:
Since the larvae remain in some of these fruit husks and then bury themselves in the ground, you should also ensure that the husks of infected fruit are collected and destroyed immediately. Otherwise, the same applies here: the aforementioned traps have proven to be an effective way of combating them. You should only use pesticides if they are actually approved in order to avoid permanent damage to the tree through improper treatment.
An overview of the most common diseases
As with many other trees, there are also diseases with the various chestnut varieties that lead to a severe weakening of the tree. As a rule, a disease attack is accompanied by a fungal attack, since the chestnuts, weakened by the disease, do not have the necessary strength to fight off the fungi. The result is slow decay, sometimes from within.
A chestnut that is affected by a disease over several years regularly loses its stability. The larger the tree, the sooner you should react in the worst case scenario, so that the tree cannot pose a threat to you, your home, or the people in your neighborhood through instability. In contrast to the pests, which occur more frequently in either one or the other chestnut species, there are hardly any differences in the diseases between the species.
❍ The Chestnut Bark Crab:
Chestnut blight is a fungal disease imported from the United States. The spores of the fungi reach the tree through wounds in the bark and spread there. The first signs are yellow discoloration of the bark and a sinking or swelling of the bark tissue. Cracks in the bark follow later and the parts of the plant above the affected areas quickly die off. Chestnut blight spreads quickly and, once it has infested a tree, it can quickly infect nearby trees as well, since it spreads through the air. For this reason, you should act at the first sign of infection.
➔ Combat:
The only way to get rid of chestnut blight is to generously cut back the affected areas down to the he althy wood. You should also regularly remove weakened branches with a cleaning cut, because weakened areas of the tree in particular can quickly be attacked by chestnut bark canker.
The best way to prevent this is to avoid unnecessary wounds on the tree and to regularly and, above all, professionally trim your chestnut. If you notice wounds on the tree, you should apply a grafting ointment or a wound closure ointment to the tree to help it heal naturally. Unless they are absolutely necessary immediately due to a fungal infestation, tree pruning should always be carried out in the cold season, as fungi do not thrive so well during this time and the risk of fungal infestation in areas that have just been cut is very low.
❍ The Ink Sickness:
This is also a fungal infestation. This disease is caused by Phytophthora species, which invade the roots, cause leaf wilt and can even cause the entire tree crown to die off. Ink-like fluid then oozes from the base of the tree, giving the disease its name. In particular, trees that stand on moist soil can be attacked more quickly, since the conditions here are optimal for the fungi.
➔ Combat:
Direct treatment at the root is difficult. One chance is spreading chicken manure liberally on the ground around the tree, as this can kill the fungus. Exposing the roots and then treating them with chicken manure also makes sense here. However, you should make sure that you avoid further root damage, otherwise the fungus will have new opportunities to penetrate the root. In general, this is also the best form of prevention.
If you notice damage to the roots of your tree, for example roots sticking out of the ground, you should treat this as soon as possible with an appropriate grafting ointment or a wound closure ointment for chestnut trees.
❍ Bleeding Chestnuts:
The bleeding chestnut phenomenon was originally observed mainly in the Netherlands, but has now also arrived in Germany. The cause is a bacterial infestation against which there are currently no really effective antidotes. You can recognize the disease of your tree by weeping and "bleeding" spots on the bark of the main trunk or on individual onesbranches. There is also discoloration of the foliage and browning and swelling of the bark around the weeping spot. If the infestation continues, there is a risk of the tree dying off completely.
➔ Combat:
Again, as with chestnut blight, only generous pruning of affected areas down to the he althy wood can really help.
However, prevention is the best way to protect your tree. For example, before you make a cut on your tree, you should disinfect the pruning tools to prevent bacteria from entering the tree wounds. Here, too, the use of appropriate grafting or sealing albums on open wounds protects the tree from bacteria penetrating these areas. If you spot an infestation, you should act quickly as there is no remedy that will reverse such an infestation and spread will inevitably lead to the tree dying completely or having to be felled beforehand for safety reasons.
Conclusion:
Effective control of diseases and pests is often difficult because agents that would be effective are not approved and the authorized agents cannot promise a complete guarantee of effectiveness against pests and diseases. However, there are a few traditional methods of controlling diseases and pests. As a last resort, pruning is required to save the rest of the tree from dying completely. However, it has also been shown that with the right care and treatment of the chestnut, many diseases can be avoided comparatively easily.