Unfortunately, boxwood does not only suffer from the boxwood moth. Here you can find out everything you need to know about combating possible diseases in your boxwood.
The boxwood (Buxus) can be found in almost every garden and park and is constantly threatened by a wide variety of pests. As a result, its wonderful leaves often discolour and the ornamental value also drops drastically. We have summarized everything you need to know about the various diseases.
Diseases not only afflict us humans, our bushes are also threatened and damaged by various pathogens. Here you will find an overview of the possible pathogens and what you can do against these boxwood diseases.
Boxwood dieback or boxwood leaf fall
The boxwood dieback has been going on in Germany since 2004. This aggressive fungus is noticeable with brown spots on the leaves and dark stripes on the shoots. Especially in humid and warm summers, gardeners often have problems with this disease.
Causes and symptoms of boxwood dieback
The disease is not only known under the name box tree leaf fall, but it is also called box tree fungus or box tree dying. The dieback of boxwood is caused by the fungus Cylindrocladium buxicola and has been driving gardeners in Germany to the brink of despair for almost 15 years now. This pathogen is capable of attacking completely he althy boxwoods and causing damage as a result. The optimal conditions for an infestation are temperatures around 25 °C and five to seven hours of leaf wetness. It usually takes place in July or August and the first symptoms appear after about two weeks, but the damage usually only becomes apparent in autumn . The fungus can persist in the soil or on fallen leaves and reinfect from the soil for up to eight years.
How do you see the symptoms of thebox tree dieback? First, brownish-orange spots appear on the leaves, which grow larger and larger. The edges of the spots are usually darker in color, and half of the leaf surface often turns brown. Black stripes are then visible on the boxwood shoots. The leaves are then shed, but fortunately the shoots remain green and can sprout again. A white spore lawn can often be seen on the underside of the leaf in damp weather. Young leaves are particularly often affected, older ones are rarely infected. If the box is attacked more often or if it is additionally weakened by frost, the shoots can die. Dark longitudinal stripes can also be seen on the shoots, which can be 0.3 to 1 mm wide.
Combating boxwood dieback
Unfortunately there is no complete protection against boxwood leaf fall, because even the he althiest plants can be attacked in a humid environment. But if you pay special attention to hygiene and have a resistant variety in your garden, you can significantly minimize the risk of infection. A particularly susceptible variety is 'Suffruticosa', this type of book suffers significantly from infection. The 'Herrenhausen' variety, on the other hand, shows more resilience and will have fewer problems with leaf fall on dry locations. If you want to read more information about box tree dieback and how to combat it, you can read our special article.
Boxwood Crayfish
Box tree canker, which is also Volutella called dieback or boxwood branch dieback, can sometimes be quite massive. The first thing you notice about this disease is growths on the boxwood, which is where the name of this disease comes from.
Causes and Symptoms of Boxwood Canker
The cause of this disease is the fungus Volutella buxi, which can cause serious damage to your boxwood. This fungus can only penetrate the box through wounds, it then decomposes the bark and the wood of the box tree.
The boxwood canker is initially recognizable by small growths at the entry points of the fungus, where the bark eventually flakes off. In addition, the shoots above the infection sites begin to wither and dry up. In most cases, only individual shoots are affected and not the entire bush. The wood around the affected area then turns greyish-brown up toblack and the leaves on these dead shoots turn light brown and hang on them for a long time when they have dried up, until they finally fall off.
If the weather is rather humid, a white, fungal coating even forms on the leaves and also on the shoots. This coating turns salmon pink when the fruiting bodies of the fungus develop. There are also sometimes red globules on the branches and leaves, which are the main fruit form of the fungus.
Fighting boxwood cancer
Unfortunately there is no difference in the susceptibility of boxwood varieties to boxwood canker, but you can simply cut back infested boxwoods and remove the diseased parts. As boxwood canker is transmitted through wounds and injuries, it is also important to keep work equipment clean, preferably disinfecting equipment with 70% alcohol.
Boxwood rust
Not only the grain in the field can be attacked by rust fungi (Pucciniales), but our beloved Buchs is also threatened by them. Older box trees in particular can be plagued by box tree rust more often than young specimens.
Causes and Symptoms of Boxwood Rust
Boxwood rust is rare, but sometimes the symptoms of Puccinia buxi can be found on the leaves in spring. Rust fungi are found on many different plants and are usually characteristically yellowish to reddish in color, but the small spots that boxwood rust forms are more brownish. These pustules are slightly convex, only about 2mm in size, and form on the top and bottom of boxwood leaves.
Fighting boxwood rust
To combat boxwood rust, it is sufficient to remove the affected shoots by pruning.
Phytophthora rot on boxwood
The boxwood is also threatened and weakened by wilt fungi, including Phytophthora rot, also called Phytophthora wilt. Particularly wet soils promote the occurrence of this root disease.
Causes and Symptoms of Phytophthora Blight
For some time now you've always heardagain from reports from America, but also from the Netherlands, that the Buchs is attacked and damaged by the egg fungus Phytophthora cinnamomoni or Phytophthora nicotinae . Phytophthora is better known as a disease affecting potatoes and other vegetables, but our evergreen shrubs can also suffer from the egg fungus.
These egg mushrooms prefer wet soil and attack the roots. Signs of them include wilting, yellowing of the leaves, and weakened growth. Ultimately, large parts of the box tree die off or even the whole box tree itself. The box tree often looks as if it has dried up or frozen to death, but the cause is "only" the egg fungus Phytophthora.
The symptoms can be confused with those of boxwood canker, but with the latter the wood of the box turns black or brown, which is not the case with Phytophthora rot.
Control Phytophthora Blight
Unfortunately, there isn't much you can do against this pathogen, other than taking preventative measures. In any case, avoid waterlogging through drainage and if you find infested plants, you should remove them from your garden immediately or destroy them.
Important mushrooms on boxwood in brief:
- Buxus dieback (Cylindrocladium buxicola)
- Boxwood Crab (Volutella buxi)
- Boxwood rust (Puccinia buxi)
- Phytophthora-Rot
In addition to the diseases mentioned above, the boxwood can unfortunately also be attacked by various pests. In our special article you will find out which pests are particularly common on boxwood and how you can combat them.
You can find out more about the box tree moth and how to combat it here.