Branch cancers and other wood diseases
In the cold season, with the insects that interrupt their activity and the bare foliage showing the entire trunk and branches, we can concentrate on observing, studying and above all in the fight against diseases of the lignified organs.
It is appropriate to classify the diseases that affect our plants into 2 macro categories: phytoparasites and phytopathogens.
The phytoparasites are, adopting a simplification, the insects; phytopathogens group together fungal diseases, viruses and bacteria.
A further subdivision classifies the pathologies by affected plant organs: diseases of the leaf apparatus, diseases of the root system and collar, diseases of the lignified organs.
Branch cancers are lesions of the lignified organs, usually localized, which appear to our eyes as real wounds on the branches of our trees.
Even if they are localized lesions, the damage caused also extends to other parts of the plant, in particular the overlying areas of the canopy; the damage is a reflection of the altered circulation of the lymph. This is why we consider this type of pathology very dangerous for our trees.
The different types of branch cancer are caused by some fungi and bacteria.
Among the most common diseases in the garden, we remember:
-the colored cancer of the plane tree: it is responsible for the bad conditions in which almost all the plane trees of the city avenues pour. Causes the lack of formation of the scar callus that heals wounds; the plant has wine or bluish wood parts. Even if the disease is linked to a fungus, usually the responsibility is to be attributed to the too aggressive and reckless pruning performed over the years, which have weakened the plant and favored the spread of the pathogen.
- chestnut cancer: responsible for damaging entire chestnut woods in our peninsula.
- cypress cancer: it affects many species belonging to the cupressaceae family and in recent years it has been very aggressive in our gardens.
- fungi of the genus Nectria: they affect various botanical species (including Malus),
the fruiting body is formed by small pink / orange balls.
- Coryneum: dangerous especially for plants belonging to the genus Prunus.
Treating these pathologies is anything but simple; branch cancers are often the consequence of planting, pruning or wrong variety choices.
Today there is a tendency to go to the agro-drug dealer, claiming to get the "magic potion" to solve the problem.
This is a completely wrong approach. If we want to stop the infections we must treat the tree with great attention and dedication: remove the infected parts, use cupric products (especially in autumn and spring), avoid water stagnation in the soil and on the plant, favor the aeration of the foliage, limit pruning, use protective pastes and disinfectants based on copper, sulfur, silicates, etc.
It is essential, first of all, to identify the cause of the tree's poor health: if the cause is, for example, excessive humidity resulting from a too shady position, interventions will never solve the problem, which will recur cyclically.
The diseases that affect trees are much more difficult to eradicate than the diseases that we can encounter in a vegetable garden or in a flowerbed of shrubs.
In particular cases, the practice of endotherapy is recommended.
The cavities cause the death of the cells of the wood, which has a hole in the inside, as if dug out of a tunnel.
The hyphae are internal, while the fruiting bodies appear externally and are easily identifiable, they can also be observed on felled plants.
- white caries: inside the wood is white and fibrous.
- black caries: it is the most dangerous, the wood is black and fractured inside. It causes sudden ruptures of entire branches.
The position of the fruiting bodies indicates the approximate location of the infection;
it is one of the most dangerous diseases especially in urban areas, identifying the trees affected by these diseases is essential to prevent high-risk situations.
An additional danger comes from the attack of xylophagous insects, which take advantage of the soft texture of the wood to dig tunnels and feed.
The hornets (Vespa crabro) that nest inside the trunks deserve particular attention: if the plant shows signs of attack by wood fungi, carefully evaluate the risk of annoying the insects with pruning or felling and eventually equip with protections suitable; the poison of these insects can be lethal to humans.
There are no particularly effective active ingredients, the same rules apply for the fight against branch cancers.
Often some of these diseases are found in home orchards, which have not received adequate care. These diseases spread among contiguous specimens also by root anastomosis (communication between the conductive tissues of two plants),
it is therefore advisable to remove an infected specimen to avoid contagion of neighboring ones.
Branch cancer and other wood diseases: Tracheomycosis
They cause damage to the lymphatic system, with occlusions of the vessels and subsequent production of tille and gums. Verticillosis, fusarium (also affecting chrysanthemum, rose and geranium), elm graphiosis are some of the types of tracheomycosis.
These pathologies also affect the root system and develop from saprophytic fungi: in addition to the recommendations previously expressed, disinfection of the soil, of the transplant clods and of the materials used in the propagation phases is necessary.