Gardening: Boxwood shoot deaths – what to do if there is a fungal attack?

Box trees are prone to fungal diseases. While fast-growing and small-leaved box trees are often robust, edging box species in particular are attacked by diseases. This is to be done on a sick plant.

  • What does a fungal infestation look like in the box?
  • What can you do about the boxwood fungus?
  • Use fungicides to prevent the fungus from coming back
  • Minimize the risk of disease
  • Nutrient richness as a recovery aid
  • Water the Buchs properly
  • Choose a more robust type of box

If your box tree is infected with fungi such as the Cylindrocladium buxicola, you should first stop the spread of spores. Otherwise it will continue to spread and can come back to you in the garden.

Protect the book from secondary diseases with the right irrigation, healthy nutrient soil and the right choice of location.

What does a fungal infestation look like in the box?

You can recognize a fungal attack on your box tree by the following characteristics:

  • dark, brown spots on old leaves and on the shoots
  • orange-brown discoloration of younger leaves
  • black stripes on the affected shoots
  • white layer on the underside of the leaves
  • The infected leaves and shoots die off
  • The surrounding leaves and shoots die off

If all of these characteristics apply, you should act immediately.

Humidity promotes fungal growth
The fungus that triggers boxwood shoot death is particularly comfortable at temperatures of around 20 degrees and with high humidity. If the temperatures rise permanently above 25 degrees and it is also very dry, this can contain the fungus.

Boxwood with cylindrocladium buxicola (Source: Getty Images / Eirasophie)Boxwood shoot death: If your hedge is infected with the fungus, it must be destroyed as far as possible. (Source: Eirasophie / Getty Images)

Causes of boxwood fungus

The nasty Buchs disease has been known in Germany since 2004 and has since spread across the country. The cause of the boxwood fungus (Cylindrocladium buxicola) and its rapid spread are primarily the change in weather: the number of days on which the weather is humid and warm has increased. Fungal infestation is also not contained and combated in good time, which is why the Cylindrocladium buxicola can continue to spread over large areas.

To prevent the boxwood fungus from spreading further, you should report an infestation in public gardens and parks to the responsible plant protection office in your state.

What can you do about the boxwood fungus?

Completely prune back a boxwood that is infested with fungi to remove fungal spores. It should not be too damp for this, because moisture promotes the disease. If a dry day is not expected in the next few weeks, cut the box promptly despite the moisture. Remove infected shoots – recognizable by dark spots and dried up leaves. In this way the pest cannot spor off; the spread is curbed.

Fungal spores can survive in the soil for up to four years. It is therefore important to treat the entire area after an infestation.

You also remove discarded leaves from your garden, because there are spores on them too. After cutting back, dispose of the cut material in the household waste and disinfect the secateurs you are using. If you don’t disinfect the device, spores will stick to it and other plants will be infected. Disposal via the compost is also taboo, because it means that the spores will continue to spread in the garden.

Prevent the fungus from coming back with fungicides

Boxwood in the light (Source: Getty Images / NitaYuko)Fungal infestation: If you discover a fungal infestation on the boxwood, you should cut off the affected areas. (Source: NitaYuko / Getty Images)

Pruning early limits the spread of fungal diseases. However, pruning does not guarantee that the fungus will not attack the healthy part of the tree in the next year. You should therefore use fungicides after pruning. By the way, the best time for this is between April and May.

Spray the book on all sides with the agent every 14 days. Fungicides cannot kill the current infestation; they only have a preventive effect. It is therefore very important that you have removed all infected areas when pruning.

So far it has not been proven that biological sprays or home remedies help against the fungus.

In addition, before using fungicides, you should have an expert check whether the boxwood disease is really a fungal attack. Otherwise, the corresponding measures may not work and were, so to speak, in vain.

Minimizing the risk of diseases – the choice of location

In addition to fungicides, suitable care can be effective in preventing fungal attack. Check the location of your boxwood: it should be a sunny, airy and not too humid place. If box trees are planted closely, they are more susceptible to fungus. Because in close planting, moisture can develop more easily, which promotes fungal infestation.

Move the boxwood if it is not airy or cannot enjoy sufficient sunlight. Please note: moving immediately after the illness is a great burden for the book. So wait a few weeks before moving.

Rich in nutrients as a recovery aid

Box needs nutrient-rich soil to thrive. Nutrient-poor soil makes box trees susceptible to disease. You should therefore create new breeding ground, which you enrich with humus. You can dig up the location of the book and mix in humus. If you want to move the box, enrich the planting hole with humus before you put the box in it.

Water the Buchs properly

Buchs must be poured in hot spells. A lack of moisture causes the plant to die. Leaves and shoots should not be touched by the water when watering. Do not water your boxwood from above through the leaves, but concentrate on the rootstock.

Choose a more robust type of box

In addition to a suitable location and an adequate supply of nutrients, you can also prevent the boxwood fungus by choosing a more robust boxwood variety. For example, the cultivars Buxus sempervirens arborescens, Buxus microphylla “Herrenhausen” (boxwood “Herrenhausen”), Buxus microphylla “Brno” (boxwood “Brno”) and Buxus microphylla “Faulkner” (boxwood “Faulkner”) are considered less susceptible. The disadvantage of the more robust varieties is that they often get brown leaves in winter.

The varieties Buxus sempervirens “Blauer Heinz” and Buxus sempervirens Suffruticosa are particularly affected by diseases.