Greening is still a disease without a cure, which is why preventive management strategies are essential and efficient in combating the disease, reducing its spread, progress and damage.
Two recent studies carried out by researchers from the United States demonstrated that preventive control is also more economically advantageous than the costs involved in remitting symptoms or attempting to cure and maintain production when living with the disease.
The significant presence of greening in orchards, especially in the state of Florida, where it is estimated that 90% of orchards have the disease, increases production costs, leading many citrus growers to discontinue some of the proposed control strategies. With the aim of achieving wide adoption by producers, the research evaluated the economic viability of the main management methods used to mitigate the effect of greening in citrus farming.
The research conducted in Florida evaluated greening management through the use of antibiotics, insecticides, foliar nutrition, thermotherapy and biological control with Tamarixia radiata in relation to the effects on fruit production and quality, comparing the cost-benefit of each.
The calculations considered the 2016-17 harvest as a baseline, as it was the most recent year without extreme weather events (hurricanes), with an average yield per tree of 1,37 boxes, and a tree price of US$11,82 per tree. box.
Comparing the costs and profit obtained, the preventive application of insecticide was the method that proved to be most advantageous – “broad-spectrum insecticides provide the only economical strategy to mitigate the impact of the disease”, explain the research authors.
With this information, it is possible to act against greening more assertively. And in “citrus growing regions where the spread of the disease is incipient, they can use the lessons learned in Florida and be more effective in dealing with HLB to avoid a similar outcome”, they add.
See the full survey: https://doi.org/10.22004/ag.econ.313310
The research conducted in Texas, which is the second region with the highest incidence of greening in the United States, evaluated young (5 years old) and adult (25 years old) pomelo orchards in different simulated scenarios: 1) without the disease; 2) with the disease and without control; and 3) with the disease and with internal and external regional control.
The methodology used analyzed the economic viability of regional control strategies – internal and external, based on plant eradication and insect vector control – in relation to the incidence and severity of the disease, yield loss, effect of mitigation efforts and economic results.
The results showed negative effects of the disease in all situations and the severity was greater in the young orchard than in the adult.
It was observed that, in the young orchard, when no control action was carried out, the incidence of greening progresses at a faster rate, reaching 100% of the plants seven years after the first incidence. On the other hand, when control strategies are adopted, the disease affects 100% of plants 25 years after the initial incidence.
Therefore, the adoption of a set of measures for preventive control of the disease proved to be essential to reduce its impact on citrus farming. “Based on the production, market and greening epidemiology scenarios considered, the adoption of an effective area-wide psyllid control strategy was preferred over the uncontrolled alternative”, conclude the research authors.
See the full survey: https://doi.org/10.22004/ag.econ.313310
The fight against greening is based on two prevention strategies so that new orange trees do not become sick: protecting the plants against the insect vector (psyllid control) and eliminating sources of inoculum (sick plants). These actions must be carried out both within and around the property.
Fundecitrus researcher Renato Bassanezi explains that both strategies need to be adopted in all areas where the disease is present. “The recommendation is that these actions be carried out jointly and regionally, with the active participation of all citrus growers in the region, also focusing on long-term results”, he adds.
When this does not occur, orchards are exposed to infectious psyllids created in inoculum sources internal and external to the property. Because of this, “and also because the results of management strategies are not easily and quickly perceived, citrus growers often believe that the methods are not being efficient and look for alternative control measures, as well as a cure for the diseased plant – the which has not yet been scientifically proven”, highlights Bassanezi. Florida, which chose not to eradicate diseased plants and search for a cure, saw production drop from 150 million boxes in 2004 to 47 million in the current harvest.
Based on these aforementioned studies and several others, the importance of preventive and regional management is highlighted. When neighbors adopt strict management standards, it is possible to increase disease control efficiency. “Therefore, cooperation between neighboring producers to control the psyllid, for example, through a joint spraying program in the region, can not only be more effective, but also contribute to reducing additional costs”, say the authors of the research conducted at Florida.
In Brazil, in the citrus belt, external biological control actions with the release of Tamarixia radiata and the replacement of plants attractive to the psyllid in urban areas have helped citrus growers, as well as the Fundecitrus Phytosanitary Alert, the largest psyllid monitoring system in the world. world - learn more about the tool: https://www.fundecitrus.com.br/alerta-fitossanitario.
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