- François-Xavier Branthôme
… but the rules vary from country to country
Tuta absoluta, ToBRFV (Tomato Brown Rugose Fruit Virus) and New Delhi Virus (Tomato Leaf Curl New Delhi Virus, ToLCNDV): these are the plant-health emergencies discussed by the European table-tomato contact group that met in Ragusa on 4 and 5 April 2019.
"Prevention is the best defence for ToBRFV"
The appearance of ToBRFV on growing sites all over the world has got the industry worried. In Italy, where the virus has been found in the southern region of Sicily, a conference was organised to discuss the issue. ToBRFV is popping up in many more horticultural locations. It is a relatively new virus and is related closely to TMV (Tobacco mosaic virus) and ToMV (Tomato mosaic virus). Almost all current available tomato varieties are resistant to both TMV and ToMV, but this new virus has broken the resistance. The symptoms are similar to the PepMV (Pepino mosaic virus).
During the conference, Guido Grasso from Confagricoltura stressed how ToBRFV is easily transmitted via contact but also via seeds, with residues remaining infected for a long time. "ToBRFV can infect tomato plants that are genetically resistant to the Tomato Mosaic Virus, meaning it is particularly dangerous for tomato crops. Short cycles are recommended to counter the virus more effectively," explained the expert.
The Spanish delegation mentioned that this virus has not yet been detected in Spain, though Tuta absoluta still persists in Almeria and Murcia, where integrated control techniques are implemented to tackle the problem. The French delegation reported how the virus does affect a few European countries but has not been recorded in France until now. They stated that to counter its dissemination, treating seeds with chlorine and using the GSPP protocol (Good Seed and Plant Practices) would be useful. Salvatore dell'Arte from Alleanza Cooperative Italiane discussed the need to harmonize the use of phytosanitary products in Europe through a specific protocol. "The Euro-Moroccan agreements must be revised with this purpose in mind as well, as some countries employ solutions that are forbidden over here."
An urgent need “to harmonize the use of pesticides within the EU”
Franco Celestre, Vice-President of the Sicilian organization Federazione degli Ordini dei dottori Agronomi e Forestali della Sicilia, added that, "in order to limit the spread of new pathogens within the European territory, it would be useful to implement measures such as using certified propagation material and resistant genotypes in order to promptly eliminate outbreaks, and employ agronomic practices and procedures useful for preventing the spread of the virus."
"It is important to harmonize the use of pesticides within the EU. We cannot be so limited in Italy, as it leads to unfair competition when it comes to costs and yields. In addition, it is not possible that Europe easily opens its borders while we can no longer export (to Canada, for example), due to the health restrictions imposed on us," stated Massimo Pavan, head of the Italian delegation.
The Spanish delegation stressed that "the regulations on pesticides are diversified for northern and southern Europe, due to obvious climatic reasons. But the inequality between countries is also and mainly due to the many active principles authorized a long time ago and only in some countries. There is a regulation on the reciprocity between countries that could enable the use of pesticides registered abroad, but the bureaucracy and limited timescales frustrate all attempts. A regulation forbidding the entrance to the EU of non-compliant products should enter into force in December 2019."
The French delegation reported an increased awareness of how the country is reducing the number of active principles in use. The objective is to progressively reach zero residues. In addition, French growers are obtaining voluntary certifications that reassure consumers regarding the use of pesticides.
Assosementi: "the only solution is prevention."
During another recent conference in Italy in late February, Alberto Lipparini, secretary of Assosementi, the Italian organisation of breeding companies, underlined the urgency of the situation. "The discovery of a new virus in Sicily which is particularly harmful for tomatoes and peppers is worrying all operators. Seed companies firmly believe in the need to work as a team and contain the spreading of this dangerous pathogen for which there does not seem to exist a solution. Prevention and good hygiene and agronomic practices represent everything that can be done", said Alberto Lipparini.
Since ToBRFV was found in Sicily, the industry has reacted speedily, providing information and training to operators in the areas affected. Two meetings were organized for technicians, growers and operators of the sector in late February. Seed companies, producers, nursery gardens and distributors attended, as well as representatives of the region's phytosanitary offices and of the University of Palermo.
"While waiting for the new virus to be characterized and for containment measures to be put in place (i.e. identification of tolerant or resistant varieties), the only solution is prevention."
Assosementi shares this opinion and believes that all operators – seed companies, nursery gardens and growers – must implement all necessary hygiene and prevention measures. "In this context, institutions, like the Regional Phytosanitary Service in particular, must do their part by monitoring the territory to assess the spreading of the pathogen and define measures to counter its dissemination."
Virologist Walter Davino explained that everything revolves around the implementation of specific practices, starting with the seed companies. "None of the actors (seed companies, nursery operators, growers, distributors) can avoid implementing all preventive containment measures: if only one link of the chain fails, it risks putting the entire Sicilian tomato production at risk."
"Seed companies must try to produce seeds in unaffected areas and perform periodical analyses on parent plants and hybrids. In addition, seeds must travel with a specific phytosanitary certificate."
"They must inspect plants regularly. Operators should not be working in several production greenhouses at the same time, and containers and soil residues that housed infected plants should be sterilized or destroyed. In addition, workers must use clean disinfected clothing and tools."
According to Walter Davino, things are more complicated for production companies "as procedures depend on whether crops are healthy or infected."
In the second case, they need to carefully remove all plants that present the symptoms and destroy them by burning them. "At least 20 plants around the infected ones must also be removed. Each infected greenhouse must be managed using specific protection and work attire. Never start by working on an infected greenhouse, but leave it for last."
"Clean clothing must be worn every day and mats soaked in disinfectant must be put in place. In addition, disinfectant dispensers must be placed at all entrances. Never assume asymptomatic plants are healthy. Small tools can be disinfected by soaking them in a non-fat powdered milk solution. Operators working in healthy greenhouses must not come into contact with those working in infected ones."
At the end of the cycle, plant and soil residue must be burned and greenhouses must be thoroughly disinfected in all areas. "Solarization is not sufficient, as it does not bring the material to 80°C."
"Distributors must check the status of the goods that come into our country. They need to collect samples from inbound goods and always demand a phytosanitary certificate attesting the absence of the virus. In addition, they must thoroughly sterilize vehicles, containers and crates", Davino concluded.
Transmission & monitoring
Walter Davino focused on the transmission of ToBRFV, discussing how the infection spreads: "Mechanical transmission is the most dangerous and is carried out by operators and pollinator insects. The virus is highly stable in the ground and waste vegetable material, while it is less transmissible via seed."
Ever since the discovery of the virus in Italy, 461 seed batches, 2080 plantlets and 54 open-field plants have been analysed. The data that emerged is interesting: transmission of the virus is extremely low for seeds and, above all, there are not many contaminated seeds. Only 36 out of 461 batches were positive to this pathogen.
Transmission is very low for plantlets as well, as only 6 plantlets out of 2080 were positive, meaning seed-plant transmission is 0.29%.
The situation in open fields is far more dangerous, as plant-to-plant transmission is due to many factors – plants touching, operators, and pollinator insects. The incidence can reach 94-95%.
During the event, Stefano Panno from UniPA talked about the PhytoCARD, a handbook drafted by Assosementi and “Road to Quality” that explains the health and hygiene rules that must be complied with in fields, greenhouses, etc. By analyzing known viruses like TYLCV and ToMV, Panno warned about how easy it is to mistake the most recent ToBRFV for these viruses.
Source: hortidaily.com, freshplaza.fr