Sharka

The sharka or Plum pox Virus (statement) is the viral Maladie more the devastator of the kind Prunus. The disease finds its origin in Bulgaria, indicated under the name of sharka which means " Variola ". Discovered on plum tree in 1932 by Atanassov, this disease was quickly propagated of Bulgaria towards the Verger S of the adjoining countries.

Description

The Potyvirus of the sharka is responsible for a Maladie plants affecting the stone-fruit species of the kind Prunus, like the Pêcher S, the Nectarinier S, the Prunier S, the Abricotier S, the Amandier S and certain decorative varieties. The Plum-Pox-Virus (or statement) does not kill the Arbre S, but it can largely affect of it the output in production of fruits. It is transmitted naturally by the means of the Puceron S and can be by other insects sucker stitchers/(but nothing is not less sure), like by the Greffage, double grafting and by the transfer of infected seedlings. The virus of the sharka does not infect nor does not affect the health of human and that of the animals. The virus of the sharka can considerably decrease the output of a harvest while making some the fruits unsuitable with consumption, by the creation of fruits having in particular deformities, coloured marks of circular forms and a very acid taste. Several plant species can be used as viral tank for the virus of the sharka, the type of tank and its effects varying according to the stock of the sharka in question, and the infected varietal species. Can be used as varietal tank various the arboricolous species of type Prunus (see higher) and various varieties of leguminous plant, such as pea leguminous plant, the tobacco, the nettle, etc

Symptoms

One observes symptoms on Feuille S, on Fruit S, wood branches and the cores. On sheets, the diffuse spots or rings chlorotic are relatively discrete. On the other hand, the fruits can be very deformed by the virus, by presenting to their surface irregular zones, delimited by more or less deep furrows, of bluish color. The flesh of these fruits, sclerified by places, is impregnated of Gomme. The wood and the cores of apricot trees can also present these rings of discoloration. In addition to the commercial depreciation of many fruits, one can assist for the varieties with purple fruits with a premature fall of the fruits before harvest. A difficulty which this disease raises is that the externalization of the symptoms of the sharka is not immediate. Concerning a fruit tree it can take place 1,2,3 years and more after the moment of its contamination.

Treatment

In the event of infection, the only recognized solution as effective consists to tear off and burn initially the trees reached presenting the visual symptoms of the sharka because of the very serious risk of dissemination of the disease. In the second place, it is necessary to create around the contaminated zone a " vacuum sanitaire" by tearing off the other plant species being used as viral reserve of the disease in order to destroy the other viral tanks of the sharka present but still invisible. With preventive measure, one can:

To locate the trees reached in winter in order to be able to tear off them before the arrival of the plant louses vectors. After checking, it was noted that the location of symptoms on branches clearly shows the presence of the virus, whatever the stock (M or D), even if the intensity of the symptoms differs according to the varieties. This location on branches, complementary to the other techniques of prospection, is thus usable to carry out prospections in winter, period interesting in practice (people available, period of long prospection).

To use Understock S, varieties or seedlings grafted, healthy. Certain plum trees GMO as C5 were developed in France and with the the United States but are not available in the trade.

To carry out treatments aphicides (anti-plant louses) according to the local councils.

To announce the cases of disease to the qualified local plant health services and to conform to lawful measurements into force.

Possible confusion

The symptoms on fruits of Sharka can be confused with those of false Sharka due to the virus of the chlorotic foliar spots of the Pommier, met on certain varieties of Prunus domestica.

Biology

There exist 4 stocks of Plum-Pox-Virus (or statement) known: Statement, statement, statement, and statement. These various stocks of statement can infect the varieties of the kind Prunus and in particular the Pêcher S, the Prunier S and Abricotier S. If the statement (D for Dideron) seems to be more pledged with the Abricotier, on the other hand the statement (M for Markus) attacks mainly the Pêcher S and it seems to be of a great natural virulence compared to stock D. the statement was detected only on the cherry tree. France knows stock statement Dideron appeared in 1969, and stock statement Markus appeared enters to the beginning of the year 1980.

Distribution

Current events

Since its discovery in 1916 in Europe, the sharka gradually invaded the majority of the areas where grow of Prunus and has to start in to extend in other countries of Europe, in the United States and Canada.

In France

Stock statement Dideron was detected in France for the first time in 1969. Stock statement as for it appeared with the beginning of the year 1980, near Living room-of-Provence between 1983 and 1984. Stock statement then appeared in the five following years, in five great areas different from great French fruit-bearing productions, of which the Rhone delta, the the Eastern Pyrenees, the Drome, the Gard and the Corsica . Since, the disease regularly developed in an alarming way until to date constituting a serious threat for the French productions of stone-fruits exits of plantation of fruit trees of type Prunus. It persists in a way alarming in the Pyrenees-0rientales, the Ardèche and the Isere and continuous to extend in Drome.

In the absence of curative treatment and while waiting for the development of alternative treatment, France and other producer countries decided that early detection and the immediate pulling up of the contaminated trees are still to date the only mode of effective fight against the virus; it is what one calls in France the collective and obligatory fight. Other countries chose as for them to let make the contamination on their premises and to adapt their production by selecting varietal species of prunus type which develop the symptoms of the sharka little and for which there is no loss of output.

In France, the French State implemented in 1993 a collective and obligatory policy to fight which rests on several principles. Initially one will seek the containment of the disease. For that, a prospection of the visual symptoms of the sharka is organized in the producers and the nursery gardeners. In the event of discovered of a low level of contaminated seedlings, those are torn off and destroyed. So on the other hand a Verger has an important rate of contamination (5% or 10% according to the departments) the whole orchard is torn off and destroyed. Then, one entrusted to INRA the mission of leading research for the setting to the point of resistant varietal species. This policy continues to currently apply, with some adaptations. In particular, the protection of an area of culture rests from now on on a prospection of the attentive sharka of the seedbeds, nurserymen and of any transfer of seedlings or grafts from the zones infected towards other parts of the territory. Any transfer of vegetable material not controlled and not profiting from a European plant health passport is in addition strictly prohibited.

Some studies suggested the possibility of transmission of the virus by the Graine (Semis of cores coming from infected trees), but the current international scientific consensus is directed towards nonthe transmissibility of the virus by this way. Work of the National institute of the Agronomic research (INRA) also highlighted the role of the plant louses " vecteurs" in acquisition then the retransmission of the virus starting from a viral tank of the sharka worms of other healthy plant species. Thus, the infected fruits can be also used to transport the sharka according to research of the INRA.

Since ten years, nearly a hundred requests were introduced in front of the administrative courts by nurserymen in order to engage the responsibility for the National institute of the Agronomic research in the introduction and the diffusion of the virus of the sharka in the south of France. Some procedures gave place for the first time in 2006 to the judgment of INRA before the Court of Appeal of Marseilles and are the subject of a recourse in front of the Council of State.

A Charter of fight and prevention against the sharka was elaborate in 2007 by the Ministry for Agriculture and the INRA and transmitted to the professional agricultural federations concerned. This Charter aimed at coordinating the efforts of all in the prevention and the fight against this virus by the detection and the early pulling up of the contaminated trees, " at the only end to break the epidemic cycle of the maladie". If the professional agricultural federations concerned recognized the utility of the principles of this Charter, they refused to affix their signature there, considering that the contents of this Charter essentially constitute a disengagement of the French State and research.

In Canada

The virus of the sharka was detected for the first time in Ontario in spring 2000. Since 2001, Agricorp and the Canadian Agence of inspection of the food their efforts to try éradiquer the virus of the sharka in Ontario linked. According to an independent committee specialists foreigners of the virus of the sharka having analyzed the results of the tests carried out in 2005, the occurrences are with the fall and its eradication is possible.

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