Dogwoods (Cornus), also known as hornbush, are shrubs or small trees with not only colorful foliage in autumn, but also colored bark. The approximately 55 known species occur primarily in temperate climates throughout the northern hemisphere and are considered very robust. Diseases and pests only occur very rarely in dogwood and are often simply the result of an unsuitable location or incorrect care.
What diseases can affect dogwood and how to treat them?
Dogwood can be affected by diseases such as anthracnose, powdery mildew and mealybugs. To treat an infected dogwood, you should radically cut back diseased parts of the plant, use fungicides or home remedies and take preventative measures.
Anthracnose usually leads to death
What is particularly dangerous is anthracnose, also known as leaf brown, which is caused by the harmful fungus Discula destructiva and mainly occurs after very rainy summers. In the initial stages, an infestation is noticeable through brown leaf tips and leaf spots and ultimately leads to necrosis on the shoots and twigs. If left untreated, this disease always leads to the death of the affected dogwood, although fungicides usually do not help. The only effective treatment method is to radically cut back diseased parts of the plant, deep into the he althy wood.
Prevent leaf browning
However, you can prevent leaf browning by following the following rules:
- Carry out pruning measures only in dry and sunny weather.
- Always only work with sharp and disinfected cutting tools.
- Always treat larger cuts with a wound closure agent.
- Water in very dry conditions.
- Never wet the leaves.
- Avoid over-fertilization - especially with nitrogen.
Powdery mildew can be easily treated
The powdery mildew - also known as the "fair weather fungus" - occurs mainly in warm and sunny weather and is noticeable through a greasy, whitish-greyish fungal growth on leaves and shoots. Fortunately, this plant disease can be controlled very well, and fungicides are not the only ones that have proven effective. Instead, you can also spray the dogwood with a mixture of (low-lime, but not necessarily rainwater!) water and whole milk in a ratio of 10:1, although this measure should be carried out on several days in a row. Infected plant parts should be cut away generously and disposed of with household waste.
Make mealybugs harmless with rapeseed oil
Mealybugs can often only be recognized when the entire horn bush is stuck and countless ants have gathered on it. The stubborn mini-animals suck out the leaf juice and excrete a sweet liquid, honeydew. The control is carried out either biologically using parasitic wasps or earwigs - the natural enemies of mealybugs - or by regularly spraying the entire bush with rapeseed oil.
Tip
Incidentally, powdery mildew overwinters on the leaves that have fallen in autumn, so that the fungus can attack the dogwood again the following spring. Therefore, after an infestation, you should always rake up all leaves and dispose of them - of course not in the compost.