Bubble on stone fruit
The blister on stone fruit is a disease caused by a fungus called Taphrina deformans. This tiny mushroom overwinters on fruit trees, especially on peach trees, hidden near the buds, or in cracks in the bark. The development occurs mainly in cool and rainy periods, with temperatures below 18 ° C; in fact, this pathology occurs mainly in the regions of central northern Italy, in the spring period. When the first buds bloom, the fungus begins its development and attacks the young leaves; the symptoms are clear and evident: the foliage appears red, or yellowish, with evident swellings similar to blisters, and thickened leaf plate, with a rigid consistency. The leaves fall within a few days, and the spores of the fungus, which appear as a whitish patina, move onto the fruit, wood or other leaves. The poor photosynthetic capacity of the affected leaves and the defoliation cause a strong deterioration of the plant; the affected fruits stop their development and fall to the ground.
How it eradicates
The fungus that causes the blister on stone fruit bears the winter cold and mild spring temperatures without problems; its development stops only when the climate becomes hot, with temperatures above 18-20 ° C, and a dry climate. Therefore, it survives on plants throughout the year, waiting for the most favorable period for its development. Generally the treatments are preventive, in order to nip the fungus when it is still in its embryonic stage, or when it has not yet attacked the plants, but simply hides on the trunk or branches. Treatments typically take place in late autumn, and late winter, before the buds swell. Some fruit qualities tend to be attacked more easily by this problem, and the cool and humid climate favors the development of fungi: in these cases, treatments are applied even when the buds begin to swell, but always before flowering.
The products to use
The stone fruit bubble is fought with specific or generic fungicides. The most classic treatments are carried out with copper-based products. Copper is a broad-spectrum fungicide, which is used against the most common bacteria and also against diseases caused by fungi; copper-based treatments are carried out when the plants have no leaves, especially on the peach tree; this is because the product can be absorbed by the leaves and have a phytotoxic effect. Plants that tolerate copper well can be treated even in late spring, but with lower concentrations of the product. Specific fungicides are also used against the problem, such as dodina, ziram or tiram; these products are also used as a prevention, during autumn or winter, from November to February; in this way we try to eradicate it before its development begins. The leaves and fruits of plants affected by the bubble must be collected and destroyed.
The stone fruit bubble develops in the first weeks of spring or towards the end of winter, in the period of the year when the climate becomes less rigid, and the plants begin their vegetative development. In this period, the mushrooms find at their disposal tender and thin leaves, in which it is easier to penetrate. But there are predisposing factors that favor the development of the disease, even at other times of the year. These mushrooms love a cool, humid climate; in particular spring periods, when the climate is decidedly cold, with maximum temperatures below 18 ° C, the bubble can reappear, also attacking already well-developed leaves or swollen fruits. Similarly, with the lowering of temperatures in late August, the fungus can restart its development, also attacking plants close to the diseased ones. Therefore, the prevention work is important, together with the treatments with fungicides to be practiced on the plants affected by the disease, in order to prevent the fungi, through the air or the rain, from moving onto other plants in the orchard.