Boxwood dieback: symptoms and measures

The death of shoots on the box tree can spoil entire gardens. A fungus is responsible for this. What can be done against the unsightly death of instincts?

The boxwood (Buxus sempervirens) can be found not only in artistically designed baroque gardens, but also in our own gardens. At Easter, even the branches of the box tree are consecrated in the Catholic Church, and in China the box tree is considered a symbol of long life. But if the book dies of instinct (Cylindrocladium buxicola) is attacked, its leaves and shoots do not have a long life ahead of them.

Boxwood dieback: causes and symptoms

In 2004, boxwood dieback was first detected in Germany and has been up to mischief ever since. The cause of leaf and shoot death in boxwood is a fungus, to be more precise Cylindrocladium buxicola. This fungal disease has been known as “box blight” in the UK since the mid-1990s and has been spreading ever since.

The first symptoms are individual brown, sometimes orange-colored spots on the box leaves, which continue to increase in size. The spots are darker in color towards the edge and flow together as the disease progresses. Black lines or streaks can be seen on the stems, and on closer inspection (for example with a magnifying glass) a white spore lawn can be seen on the underside of the leaf.

The box tree then sheds its leaves and the shoots become bare. Therefore, the dieback is also called "boxwood leaf fall".

Boxwood dieback: course and consequences

The prerequisite for infection is that the leaves are moist for at least five hours. The optimal temperature for this fungus is 25 °C, but it stops growing at temperatures above 33 °C and below 5 °C.

When spores come into contact with the moist boxwood leaves, they germinate after just three hours due to the moisture and grow directly into the plant tissue, wounds are not necessary for this. The infection of the plant can happen after 5 to 7 hours. After about a week, the symptoms will appear and the leaves will begin to fall off. As already mentioned, a white fungus lawn forms on the underside of the leaves. From there, the spores are spread by splashing water. The mushroom Cylindrocladium buxicola survives on fallen leaves in the soil by forming spores called chlamydospores. These spores can survive in soil for up to four years.

It is also possible that the boxwood carries the disease but does not show any symptoms. It is not yet known which environmental conditions are responsible for the disease breaking out.

Boxwood dieback: Measures against dieback

So what should you do to protect your beloved boxwood from dying instincts or, if it is already affected, to free it?

Boxwood dieback: take precautions

The prevention of fungal diseases begins with planting. Since the dieback needs moisture to break out, it is best to place your boxwood in a light and wind-free place so that it can dry off quickly.

Choosing the right plant can also prevent fungal infestation. Because there are also boxwood species that are less susceptible to dieback. These include, for example Buxus sempervirens var. arborescence and the two Buxus microphylla- Sorts '. The types of box that are particularly susceptible are 'Blauer Heinz' and 'Suffruticosa'.

There are also a few things to consider when caring for your boxwood. If you water your box, it is best to water it close to the ground. Do not wet the entire boxwood with water, only the soil near the base of the trunk. Sprinkle the entire box, create optimal conditions for the dreaded fungus. At the Pruning of the box hedge you should always pay attention to the weather. If you do not cut on warm, humid days, the injured leaves and shoots are particularly at risk of being infected by fungal spores. Boxwood hedges that are very dense and shaped are particularly difficult to dry and should therefore never be cut when it is wet.

Boxwood dieback: Measures to be taken in the event of an infestation

An important point in combating shoot dieback is the removal of infested plants. If the drift dieback has spread in your garden, you must remove the diseased plants and the remove fallen leaves and either dispose of them in the residual waste, burn them, bury them deep or professionally get disposed of. The pathogen is also in the soil, so you should also consider removing the top layer of soil. In addition, you should no longer plant boxwood in these infested areas. If you still don't want to do without a box tree in your garden, you should try to plant healthy plants in yours To propagate in the garden yourself in order not to cause shoot death again through purchased, possibly infested plants to spread. Here you will also find beautiful alternatives to boxwood, which dieback cannot harm.

If you have handled infested plants, you should also thoroughly clean tools and clothing, preferably disinfect them. Otherwise, you could transmit the disease to healthy box trees yourself.

Boxwood dieback: Suitable pesticides

Boxwood dieback can be combated or prevented with pesticides containing the active ingredient tebuconazole.

This active ingredient is found in many products, such as Baymat mushroom-free. The optimal application period is from April to October. The agent has a systemic effect against many different fungi on roses and ornamental plants. This means that the active ingredient is absorbed after spraying and then spreads throughout the plant. However, this remedy should not be used on boxwood more than six times a year, with an interval of at least one week between applications.

The product Curamat Rosen-Pilzfrei can also be used against boxwood dieback. It also contains the active ingredient tebuconazole and it is injected. Here, too, the maximum application is six times a year and the spraying interval is at least seven days. The application should be done at the beginning of the infestation or when the first symptoms become visible.

Unfortunately, the use of tebuconazole can be harmful to some beneficial insects, such as predatory mites, crepe wasps, ladybirds or parasitic wasps. If you have introduced these beneficial insects into your garden to control other pests, you should reconsider using one of these fungicides.

Boxwood dieback: possibility of confusion

The volutella-Branch dieback, that of Volutella buxi is caused can easily be confused with the death of instincts. The leaves dry up, turn a pale green color and a pink spore lawn forms on the underside. A clear distinguishing feature, however, are the. These streaks only appear when the shoots die off volutella but not.