The Peach Bubble
Leaf blister is a fungal disease caused by various causative agents belonging to the Taphrina genus. The genus includes over 150 species, the most common of which in agriculture are:
Taphrina aurea (Poplar Bubble)
Taphrina bullata (Pear Bubble)
Taphrina carpini (Carpino Bubble
Taphrina cerasi (Mirabolano Bubble)
Taphrina deformans (Peach Bubble)
Taphrina pruni (Plum Bubble)
Taphrina ulmi (Elm Bubble)
Etiological passport Kingdom: Mushrooms
Division: Ascomycota
Class: Taphrinomycetes
Order: Taphrinales
Family: Taphrinaceae
Type: Taphrina
Species: T. deformans
Peach leaf curl is the main fungal disease affecting peach trees, caused by the etiological agent Taphirina deformans but capable of causing damage also to other fruit plants belonging to the family of Rosaceae Such as apricot, cherry, and almond. The fungus is widespread throughout the Italian peninsula, but it is in the northern regions that, thanks primarily to the more favorable climatic and environmental conditions, it is able to manifest the most dangerous infections. If not preventatively controlled, this disease can compromise the entire annual production, and furthermore, when it appears in spring, it is almost always too late to intervene.
It is the most serious peach disease due to the irreversible damage it causes to the leaves. Once the fungus has developed, the leaves dry up and fall to the ground, impoverishing or eliminating the year's production and often reducing the following year's yield due to the indirect damage to the wood if timely treatment is not applied. The disease appears when the first leaves appear, and even later if the seasonal climate is favorable for fungal development. Affected leaves can be recognized by their characteristic blistering deformations and abnormal reddish coloration. Leaf deformations caused by blisters are often confused with aphid attacks, which can cause very similar leaf deformations. However, in the case of blisters, the leaf becomes not only deformed but also fleshy to the touch and crunchy – fragile; furthermore, aphid attacks can be recognized by the presence of aphids on the underside. This disease mainly attacks the leaves, but can also affect flowers, fruits, shoots and twigs .
SYMPTOMATOGRAPH
Leaves: Leaf attacks can also occur after bud break ; in these cases, the symptoms manifest themselves in the same manner as described for the leaves of the shoots. The leaves are only partially affected, and more importantly, the attacks do not significantly compromise shoot elongation. The first symptoms of the blister can be observed on newly opened leaves, which present blisters located near the central vein. As vegetative development progresses, the blisters increase in volume and tend to merge, while the affected tissues take on a fleshy consistency and are thicker than normal leaves. Simultaneously with the structural changes, a change in tissue color also occurs, initially taking on a yellow-chlorotic hue that later becomes reddish. The morphological deformations of the leaves, caused by attacks by Taphrina deformans, lead to a reduction in photosynthetic capacity, resulting in plant deterioration, the effects of which can persist into subsequent years. Affected leaves and shoots develop a wrinkled, blistered surface, almost shiny on the underside; subsequently, the transparency disappears and the leaf takes on a dull, velvety appearance. When observed under a magnifying glass, a whitish mold appears, resulting from the sexual fructification of the fungus.
Flowers: Flowers are rarely affected by the disease, but in susceptible "nectarine" varieties, and in cold, humid, and rainy springs, symptoms may also appear on this organ. In particular, the flowers can transform into fleshy, deformed clusters, resulting in drooping. The plant experiences a significant loss of flowers, and those that do set (turn into fruit) produce stunted, small, and bad-tasting fruits, due to insufficient nourishment from the leaves, even if not directly affected by the pathogen. If they are attacked by the fungus, however, they present malformations that mimic the leaf symptoms.
Fruit: Fruit is attacked sporadically, especially during the growing season. However, in the most susceptible varieties (nectarines) and in humid, rainy, and cold springs, infection can occur with symptoms similar to those of the buds and leaves. Fruit, especially if affected during the growing season, exhibits areas with a corrugated surface (cerebri forme), blistered, orange-red in color, raised above the fruit surface. These areas may show rot or lesions caused by other fungal agents. Fruit affected by the blister do not ripen properly and are inedible . If the fruit is affected early, that is, during the post-fruit setting stage, it will drop immediately.
BIOLOGICAL CYCLE
The ideal thermohygrometric conditions for infections are:
- Average temperatures < 15°C « during the leaf wetting period », and < 18°C once this phase is over.
Attention!!!
When we talk about wetting, we're referring not only to rain, but also to other phenomena such as fog. Furthermore, it's important to keep in mind that dry periods lasting less than four hours cannot be considered an interruption in wetting.
Attention!!!
Peach leaf curl is a disease that can be prevented in the autumn and winter, during the saprophytic stage of the fungus. Therefore, by spring, when the buds open, it may be too late to intervene.
Preventive control against peach leaf curl is carried out before the buds open.
2nd Treatment: Performed in late winter (late January – February)
3rd Treatment: (optional) Performed between the swollen bud stage and the pink bud stage.
Attention!!!!
If the three preventive treatments are followed, it is very difficult to find attacks by the fungus, although for particularly sensitive cultivars (yellow-fleshed varieties) some spring treatments (post-fruit set) may be necessary.
Peach leaf curl protection, combined with the fight against corineum and various other fungal diseases, forms the basis of the fungicide protection of this crop.
The "burno" treatments (1st - 2nd treatment) are aimed at drastically reducing the mass of inoculum present on the plant.
The two traditional "brown" treatments can be followed by one or two treatments during the growing season, usually during the bud break and fruit development stages, using 0.2% Ziram. These spring treatments reduce the potential for inoculum but do not stop the disease and are therefore only justified if severe blister attacks are observed on the foliage.
WHICH PRODUCTS TO USE?
a. Cuproxat® SDI "OK in organic farming"
b. Fruttene® 76 WG
c. Tebusip® Combi
d. Zetaram® New Tech
e. Ziramit 76 WG (Ziram)
f. Triscabol DG (Ziram)
3rd Treatment: Calcium-based products
to. Polysenium calcium polysulfide
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