The Content Of The Article:
- Symptoms and course of the disease
- Preventive measures
- Combating boxwood dying
- Video: Shape cut in the boxwood
Especially in warm, humid summers, the boxwood shoot extinction, a fungus with the Latin name Cylindrocladium buxicola) is spreading rapidly: The leaf surface must be moist for at least five to seven hours continuously, according to studies in England, where the pathogen first epidemic-like occurred in 1997 - only then can the fungal spores penetrate the thick wax layer of the evergreen leaves and infect the plant. The boxwood mushroom begins to grow from temperatures of five degrees. At about 33 degrees, however, the cells die off.
Symptoms and course of the disease
First, dark brown spots appear on the leaves, which quickly grow larger and merge. At the same time numerous small white spore camps form on the undersides of the leaves. In addition to the black longitudinal stripes on the shoots, these are the safest distinguishing features of the disease.
By comparison: in boxwood crayfish (Volutella buxi), the spore beds on the undersides of the leaves are larger and orange-pink, in the boxwood wilt (Fusarium buxicola) the bark turns dark over a large area. Also typical for Cylindrocladium are the strong leaf fall and the dying of the shoots in the advanced stage of the disease.
Important are a sunny, airy location and a balanced supply of water and nutrients. Always water the box trees from below and never over the leaves to avoid them becoming unnecessarily wet. On warm, humid summer days you should also refrain from pruning, because the injured leaves make it particularly easy for the fungus to penetrate. If this is unavoidable, it is highly recommended to use a suitable fungicide for valuable box hedges after cutting the shape.
Choosing the right variety also helps to prevent infestation: most of the more vigorous boxwood varieties such as Buxus sempervirens 'Arborescens' and 'Elegantissima' are resistant, as well as low-growing varieties of Asian small-leaved boxwood (Buxus microphylla) such as 'Herrenhausen' and 'Faulkner' '.
In contrast, the popular edging book (Buxus sempervirens 'Suffruticosa') as well as the edging variety 'Blauer Heinz' are very susceptible. Cut plants do not dry so easily because of their dense growth and are therefore more susceptible than uncut ones. It is striking that the infection begins in dense, box-shaped borders always on the horizontal top, because here the water is the longest after rainfall.
Meanwhile, it has also been found that there are plants that carry the pathogen latently in itself. When and under what conditions he breaks out, however, is largely unclear. For this reason, it is always risky to bring new boxwood from the nursery in the garden. If possible, you should multiply your boxwood yourself, because this is the only way to ensure that the mother plants are healthy.
The fungus attacks not only the leaves, but also the shoots - hence the German name Buchsbaum-Triebsterben
Combating boxwood dying
In case of slight infestation, you should immediately cut back the affected bushes vigorously, then disinfect the scissors (for example, with alcohol) and dispose of the clippings with the trash. Also all fallen leaves must be removed very thoroughly from the bed and disposed of in the household waste, since the spores can survive on it for several years and are still contagious even after four years.
Then treat the plants cut back into the healthy shoots immediately with a fungicide (fungicide). Preparations such as rose-fungus-free Ortiva, Duaxo universal fungus-free and fungus-free Ectivo show a preventive effect against the boxwood dying. If you then treat the new shoot several times at intervals of 10 to 14 days, you can protect the young shoots from re-infection. It is important to change the preparations with each treatment in order to avoid resistance. Although environmentally compatible copper preparations are also effective, they are not approved in the home garden for the treatment of ornamental plants.
Tip: If you want to be on the safe side, you should plant other evergreen shrubs with a box-tree-like appearance. As alternative plants for the boxwood are suitable for example the evergreen honeysuckle (Lonicera nitida), varieties of the Japanese husk (Ilex crenata) as for example 'Convexa' as well as dwarf forms of the yew as the very weak growing enclosure variety 'Renkes Kleiner Grüner'.
Video: Shape cut in the boxwood
Editor Dieke van Dieken shows how to give a boxwood a neat shape cut.