Also called white mal, hatred is a fungal parasite that attacks the foliage of many fruit and ornamental plants; particularly affected are the vines and roses, but we can see their presence throughout the garden. It is a disease that particularly affects plants grown outdoors, as it develops on the foliage that remains wet in case of strong temperature changes, this type of conditions practically never occur in the apartment, while in the garden they are present for most of spring and even early autumn.
Oidium is easily diagnosed even by those who do not intend to gardening, as it manifests itself as a thin white or greyish mold, which covers the foliage like an impalpable flour. It first attacks the foliage, but it can spread up to buds and fruits, ruining them beyond repair.
Oidium: How to fight it
The bad white is weakened by spraying the foliage with wettable sulfur; such treatments are practiced starting from the beginning of spring, when the morning sun is hot but the climate is still fresh; these treatments are repeated fortnightly until late spring, however, avoiding the periods in which the plants are in bloom, as the sulfur on the foliage tends to remove bees and other useful insects. Often sulfur-based treatments are repeated in late summer-early autumn.
This type of treatment is generally sufficient to completely eradicate the oidium or even not to allow it to appear.
During the flowering period it seems that the use of bicarbonate to vaporize the foliage of ornamental plants inhibits the development of oidium, but this method does not always seem to be effective.
In the case of grapevine cultivation to combat hatred, an antagonist fungus, called Ampelomyces quisqualis, is also used, which seems to prevent the development of white disease; it is used above all in late winter, when the temperatures are still very low.