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The evergreen boxwood has been an integral part of European gardens for centuries: the pruning-tolerant tree is particularly popular as a high or low hedge or as a topiary. In particular, the common boxwood (Buxus sempervirens) with its estimated 60 varieties can be found in many gardens. The heat-loving shrub, which grows up to eight meters high, is comparatively easy to care for and hardy, but also very susceptible to all kinds of diseases and pests.
The box tree moth causes great damage
Diseases
When it comes to diseases, problems caused by various fungi dominate, many of which have only been on the rise for a few years and threaten valuable stocks. Combat is often difficult.
Boxwood dieback (Cylindrocladium buxicola)
Probably the most feared disease of the boxwood is the boxwood shoot dieback caused by the fungus Cylindrocladium buxicola, which is initially manifested by rapidly growing, dark brown spots on the leaves. At the same time, white spore deposits form on the undersides of the leaves, which, along with the black stripes on the shoots, are a clear identifier. In the later course, leaves fall and shoots and entire parts of the plant die off. Prevent the disease by taking the following measures:
- Choose an airy location that is as bright as possible.
- Ensure an adequate and balanced supply of water and nutrients.
- Always water the boxwood from below, never wet the leaves.
- Do not prune boxwood in warm, humid weather, as this promotes fungal infestation.
The 'Suffruticosa' and 'Blauer Heinz' varieties are particularly susceptible to this disease. Instead, you can plant less sensitive variants of the small-leaved boxwood (Buxus microphylla), such as the popular 'Faulkner' variety.
Boxwood canker (Volutella buxi)
The fungal pathogen Volutella buxi, which causes the so-called box tree canker, is spread as a result of incorrect pruning or the use of contaminated garden tools and cutting tools. You acknowledge an infection
- initially attached and twisted leaves
- These initially turn brown and then fall off.
- Whole branches later dry up.
- Orange pustules also develop.
- Spore deposits can be seen on the undersides of the leaves and on the shoots.
In the event of an illness, you should cut back the affected plant deep into the healthy wood and dispose of the infected cuttings with the household waste.
Boxwood wilt (Fusarium buxicola)
In contrast to other fungal diseases, boxwood wilt caused by the fungus Fusarium buxicola is usually limited to individual parts of the plant. These initially show a yellow discoloration and then die off. Typically, dark, soft spots can also be seen on the bark. It is usually sufficient to cut out the affected areas.
Boxwood rust (Puccinia buxi)
The boxwood rust, which occurs rather rarely, mainly affects older stocks of the common boxwood (Buxus sempervirens). An infection initially goes unnoticed for a long time, since the causative fungus Puccinia buxi is initially limited to the inside of the plant. The leaf tissue only shows thickening at first, while the rust-red, conspicuous spore deposits only appear months later. They mainly appear in autumn. Affected plant parts are highly infectious and should be removed and disposed of immediately.
pests
Lice, mites and fleas that suck leaf sap are common on boxwood. To prevent an infestation, you should ensure optimal location and growth conditions. Pests primarily colonize weakened specimens. Many of the animals listed here overwinter directly on the plant, mostly in the form of eggs or larvae. Effective control therefore includes pruning infested box trees in spring before the larvae hatch. This should be done by mid-May at the latest.
Box tree moth (Glyphodes perspectalis)
The box tree moth, imported from East Asia, has only been active for a few years, but is a massive threat to the box tree. The larvae of the small butterfly, which only lives for a few days, are particularly damaging to plants and eat the plants bare within a short time. Since the green caterpillars live inside the bush, an infestation is often only noticed very late. Control is difficult because numerous generations hatch each year and plants are repeatedly infested even after successful treatment. The following measures have proved their worth:
- Remove caterpillars with a high-pressure cleaner (€119.90), leaf blower or vacuum cleaner
- Application of the bacterium Bacillus thuringiensis, which kills the caterpillars
- However, this requires good timing as this does not work every time.
Dusting the whole plant with algae lime also shows good results in the short term.
Boxwood flea (Psylla buxi)
If the young leaves curl up at the tips of the shoots - the so-called "spoon leaves" - this is a typical sign of an infestation by the common boxwood leaf flea. In the summer, the adult animals lay their eggs in the leaves of the boxwood, where they overwinter and the larvae hatch from them in the following spring. In the event of an infestation, the affected parts of the plant should be cut off in late summer or autumn.
Boxwood spider mite (Eurytetranychus buxi)
The boxwood spider mite, which has also only been appearing for a few years, only appears in dry and hot summers. It can be easily combated with predatory mites and with preparations based on neem or rapeseed oil. Clearly recognizable, yellowish galls in the leaves, on the other hand, are a sign of an infestation with the gall mite (Monarthropalpus buxi), which should be cut back vigorously in spring.
tips
To save yourself the hassle of diseases and pests, you can also choose similar plants such as barberry or privet as a substitute instead of the boxwood.