Question: peach bubble
How can I treat my peach against the bubble?
No preventive treatment has been done and now it already has a lot of fruit.
Are there any suitable products?
With the popular name of the bubble of the peach tree indicates the disease that most commonly and heavily affects the peach tree. The pathogenic agent that causes it is Taphrina deformans, an ascaromiceto, meaning a fungus. It is capable of causing damage to all the green organs of the plant, ie leaves, flowers, buds and fruits and can significantly affect production both in terms of quality and quantity.It is a common disease in all regions of Italy because almost everywhere during the growing season there are climatic conditions suitable for its manifestation and spread.To the inexperienced grower the symptoms may seem similar to those of a strong attack of aphids, but, as we will see, there are unequivocal traits that, if we want to dedicate ourselves to the cultivation of this fruit, we must learn to distinguish.Symptoms of the peach bubble
The first symptoms can occur at the beginning of spring, when the buds are opened (generally it is referred to as "rose bud"). If the attack has already occurred, the shoots will immediately appear deformed, wrinkled, with colors that change orange, dark red and purple. As they develop they will notice bullous formations and to the touch they will be fleshy and very fragile. Later in the season, the leaves are usually also attacked. The symptoms that occur do not differ from those affecting the shoots. Also the leaves will manifest numerous boils and will be easily damaged by touch. Furthermore, the lower page will appear translucent or almost transparent. The upper page, instead, usually quite shiny, will take on a very opaque appearance caused by the presence of the fructification of the fungus.
In addition to this there are also chromatic modifications. Initially, green becomes lighter, almost chlorotic. Later on, in correspondence of the bubbles, reddish or orange areas will appear. This phase significantly damages the tree because the leaves lose much of their surface and consequently the chlorophyll photosynthesis is heavily influenced. The plant remains without energy to complete the fruiting.
In the event of massive attacks, the fruit may also exhibit malformations and color changes.
The spores of the peach bubble winter in two different forms, the sexual (ascospora) and the asexual. Both nest in the bark of the plant, in the area of the buds, on the twigs or even on the ground on fruits of the previous year gone into decomposition. Even the old leaves on the ground can be a vector.
When the spring season arrives, especially if there are frequent rains or strong environmental humidity and the temperatures are ideal (around 8 ° C) germination occurs with the production of a premicelic tube that pierces the vegetable surface. The mycelium then moves into the tissues and begins its activity. Enzymes are therefore produced which, in addition to promoting nourishment, induce physiological mutations in parasitized tissues.
The fruiting bodies that form the patina on the affected parts and in particular on the leaves are released.
After the breaking of the buds and the sprouting if there are temperatures below 15 ° C and many rains or persistent fog (the high rate of humidity must remain for at least one day) the spores begin to move and to nest in other organs previously not infected. If the temperatures are constantly below 18 ° C, the disease is free to continue to spread and cause ever greater damage: from the drop of flowers to the missed fruit setting. The leaves lose their peculiarities and become more and more fragile, until they fall off prematurely. In the most extreme cases it is possible to reach the complete defoliation of the interior of the tree
Finally there is the saprophytic phase, that is the phase in which the mushroom produces its own fruits (the white patina) and prepares itself to face the winter period to hit again in the coming year.
Peach bubble development
As we have said, the spores can overcome the cold period by taking refuge in crevices, especially in the areas of the buds, in the splits of the bark and on the top of the twigs.
Development in early spring occurs when there are rather low temperatures and strong environmental humidity. If the temperatures in February-March exceed already 10 ° C and the rains / mists are scarce there will be hardly any early attacks.
If there is development, its action remains constant until 25 ° C is exceeded, even if the optimal temperatures range from 15 to 18 ° C.
When the 30 ° C is reached, the fungus dies and generally with the arrival of summer it does not cause more damage. To reach this stage unscathed, however, a whole series of strategies must be put in place to reduce or, even better, eliminate its impact during the winter-spring period.
Prevention and fight against the peach bubble
Unfortunately still at present there are no active ingredients available that can cure the disease and block its spread in a powerful and effective way, especially when the environmental conditions are extremely favorable. The strategies that are mostly adopted are the preventive ones that are based on the fight against the establishment of spores and the attempt to prevent them from overcoming the winter on the plant's tissues.
Timing of the interventions
- The first preventive treatment "brown" should be done in late autumn, when the plants are completely stripped from the leaves
- It will then have to be repeated at the end of winter (depending on the regions at the end of January or mid-February)
- A third operation (advisable if there have been serious diseases in previous years or if we have plants particularly subject to this disease, such as nectarines) should be carried out as soon as we notice the first swelling of the buds and in any case before reaching the pink buttons.
- In case of serious attacks on the vegetation it is possible to intervene with bland doses (0.2% of ziram) two or three times in the phases of fruiting and growth, keeping in mind that these treatments hinder the spread of the disease, but they are not healing.
Let us remember that for the treatments to be really effective it is necessary that they dry completely on the plant. This only happens if there is no rain for the next 24 hours. If during this time there were more or less heavy precipitations it will be necessary to repeat the procedure if you want to be sure of being covered.
It can be very useful, especially if infections are repeated year after year, eliminating the first plant shoots in spring.
Clearly the cleaning of the orchard in autumn or at the end of winter is fundamental. Since the wintering spores are able to remain active on the leaves on the ground and also on the fruits it is well to devote themselves carefully to the removal of all the material, including the branches deriving from pruning. The ideal is to proceed burning them. If the regulation of our municipality does not allow it, we transport it to a greenhouse disposal center.
For a complete disinfection you can also proceed with a vaporization on the ground of the same products used on the foliage.
Currently the most commonly used synthetic products are ziram (dimethyl dithiocarbamates), dodine and captan.
In organic farming, autumn treatments are also carried out with copper-based products
- Cupric sulphate: usually it is not used in purity due to its phytotoxicity and to its poor persistence.
- Bordeaux mixture: in practice it is cupric sulphate more or less neutralized by the addition of calcium hydroxide. Once it was mixed directly, today ready-to-use formulations are available which can be used in combination with other active ingredients (eg insecticides) to reduce the number of interventions.
- Copper oxychloride: it is less toxic than cupric sulphate
The use of cupric is an excellent choice as they are very effective on this type of pathogen. We can however add that they are the product of choice for many other diseases and therefore their use is polyvalent helping us to defend the plant from different physiopathologies with a single intervention.
At high doses, however, especially for peach trees, copper is phytotoxic. It is therefore good to use it only in mild doses during the winter period and avoid using it on vegetation.
In organic farming, since it cannot use synthetic products, calcium polysulfide can be used at this stage. The use of other pesticides during spring and summer, especially those based on sulfur (useful for monilia and oidium) have the advantage of considerably reducing the inoculum and therefore are a positive factor.
Choice of varieties
If in our area the problem is widespread due to predisposed climatic factors it is good to insert plants with proven resistance and avoid particularly sensitive varieties such as nectarine peaches or yellow-paste peaches.
An aspect to pay attention to, both as a preventive element and as a remedy in case of attack by the bubble, is that concerning the peach pruning. The bubble, in fact, develops due to a fungus and the fungi find fertile soil with conditions of greater humidity and shade. Proceeding with a correct pruning you can therefore have a good aeration of the foliage and branches, which will have a better exposure to sunlight and a lower probability of being affected by the fungus. Pruning the peach is also fundamental to eliminate the most affected branches, so that the pathology spreads as little as possible. It is good to remember that to avoid the spread of spores it is necessary to proceed with the destruction of the cut branches by burning them. It should be remembered that pruning develops in two phases, one in winter and one in summer. In winter operations the branches of the same year are cut, as the peach tree produces fruit on the branches of the previous year, with the summer pruning, instead, the branches are removed that do not allow a good breath of the foliage. This intervention is generally carried out in July.
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