The list of diseases that can attack ornamental trees is long. However, there are several measures you can take to avoid the attack of all these parasites.
Some of the most destructive pests are Armillariella mellea, a parasite fungus that can cause serious damage to ornamental trees where there is a high proportion of weak or damaged trees, being more common in humid soils or in the proximity of recently felled areas. Another of the most feared pests is fire blight, fortunately it is almost unknown in Spain, this disease causes the death of countless Rosaceae (Pyrus, Prunus, Malus, Cotoneaster, Sorbus, etc.)
The dimensions of the trees sometimes oppose the application of treatments that are necessary. While they are small, a simple spray is enough to apply the treatment to the tree, but once the tree develops, you must take other measures, such as prevention.
The best defense is prevention, most of the plagues enter the trees by bad cultural habits, that is to say, pruning carried out in moments of high bacterial or fungal activity. To do this, avoid pruning on windy or rainy days, as fungi and viruses will enter more easily on these days. Anyway, after a pruning, if the wound is big, it is convenient to cover it with a product that prevents the entrance of fungi and the accumulation of water, because it could be the case that the wood rots if the water enters through the wound.
Other disorders such as deficiency diseases, due to soil deficiencies, chlorosis caused by excess lime, cold attacks or sunburn, may give the appearance of parasitic diseases; having decided on the treatment to be carried out, it is first advisable to determine the nature of the damage.
One of the best ways to keep the garden in good condition is through hygiene, removing dead, diseased or damaged branches and treating and healing wounds. With this care the trees are able to resist in the best conditions to the attacks of the parasites.