Karin Solomon
(Orange with CVC or "yellow." Disease causes damage of $ 100 million per year)
They are tiny, invisible to the naked eye. But cause losses of millions of dollars a year to citrus growers. Diseases CVC (or "yellow") and Huanglongbing (HLB or greening), caused by Xylella fastidiosa and Candidatus Liberibacter americanus, respectively, have no cure and generate very high losses to the farmer.
According to data from Fundecitrus, São Paulo has approximately 600 000 hectares for the citrus industry, with approximately 200 million plant. Of these, 40% have symptoms of CVC and 6.9%, symptoms of greening. Two-thirds of the state's orchards are infected with the bacterium that causes greening.
The CVC has cost management of 100 million dollars per year in the state of São Paulo, between lost productivity, planting new seedlings, use of pesticides to eliminate the insect vector - the cicada -, and eradication of infected plants.
In the case of greening have been more than 20 million plants eradicated. "But we do not know, yet, how much it means for total loss," says Marcos Machado, coordinator of studies on Citrus greening Center. "Because the disease is extremely severe and kills the plant, the expected loss is much higher [than the harm caused by CVC]."
Antonio Juliano Ayres, manager of research and development Fundecitrus, calculates that outside the shipping amount, half the cost of production is bound to treat diseases. For him, this is something very serious because, "although the State of São Paulo has extraordinary conditions for production and is the largest producer in the world, almost all serious diseases are present here in São Paulo citrus."
The CVC was first identified in 1987 in the northwest of the state of São Paulo. Since then, research has advanced greatly over its causes and effects. The bacterium Xylella fastidiosa is transmitted by the leafhopper insect and is housed in the xylem of the plant, vessel that carries water and nutrients. There, the bacteria multiply and unite, blocking the movement of the vessel. Therefore, the plant begins to yellow; symptoms were once mistaken for drought. While in Brazil the bacteria attacks mainly citrus, such as orange, in the United States affects vines. Plum and coffee trees are also affected by variations of the bacteria.
The greening was identified only in São Paulo in 2004, although there are already events for over 100 years, according to Ayres, the Fundecitrus. The causes of the disease are not yet fully proven. However bacteria prevents the full maturation of the plant which remains green, and causes productivity loss.
Research
Citrus Center researchers have developed an amino acid that can reduce the multiplication of the bacteria causing the CVC. The amino acid is in use for four years and has no environmental impact. Are also testing improved plants and more resistant, being planted to evaluate the producer.
According to Professor Paulo Zaini, Institute of Chemistry, University of São Paulo, has been much progress in genetic research of Xylella fastidiosa. Research on the mechanisms of action of the bacterium that causes CVC are also advanced. The professor studying a specific protein, which allows the bacterium Xylella fastidiosa to stick to the vessel wall and to each other.
The long term plan is to create another protein that prevents the action of adhesion of bacteria. Despite this progress in research, the teacher evaluates that a rational solution, which directly attack the bacteria, still takes 10-15 years.
Control
While many scientists studying actions to directly combat the bacteria, disease control is still mainly done by citrus growers. It is important to use healthy seedlings, grown in controlled greenhouses. Furthermore, the vector control by means of pesticides applied at the edges of orchards is also recommended. Finally, it is necessary to make constant inspections at least four per year. When you find a mature plant with symptoms of CVC, the branch can be pruned. In the case of young plants or seedlings, must be eliminated. By identifying a plant with symptoms of greening, it should also be eradicated.
Source: Globo Rural magazine
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