Low supply increases the price of pear oranges in Brazil
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Greening is considered the worst disease in the world's citrus industry, causing serious damage to production, and there is no cure. In Brazil, the losses are enormous: in the last five harvests, more than 66 million boxes of oranges were lost in the citrus belt of São Paulo and Triângulo/Southwest Minas Gerais, the main fruit producing region in the world, according to a survey by the Defense Fund of Citriculture (Fundecitrus).
As there is no treatment for the plants, the research sector focused on ways to prevent the disease. The biological control created in Brazil by Esalq/USP and perfected through a partnership between Bayer's agricultural division and Fundecitrus has stood out with the release of small insects — wasps called Tamarixia radiata — in non-commercial areas, that is, outside of producing farms.
According to Fundecitrus, the average incidence of orange trees with greening symptoms in the citrus belt is 22,37% (7,2% more than in 2020), which corresponds to more than 43 million trees.
From August onwards, Brazil entered the phase considered essential for combating the disease. This is because, during the end of winter and spring, the pest known as psyllid (Diaphorina citri), an insect vector of the bacterium CandidatusLiberibacter spp., which causes greening, reaches its population peak.
Fundecitrus researcher Marcelo Miranda, coordinator of the institution's Entomology area, explains that greening control requires the adoption of several joint strategies, inside and outside the orchards, and that biological control is another sustainable tool, for external areas to farms.
“The greening management package provides for the use of healthy seedlings, inspection and elimination of trees with symptoms and control of the psyllid, among other measures, in an integrated manner. However, in addition to acting within the property, it is necessary for the citrus grower to carry out external actions, which consist of replacing the psyllid's host plants [citrus and myrtle] with other non-host plants and also controlling the insect around the farms. And it is this last point that includes the use of the T. radiata wasp, a natural enemy of the psyllid,” he says. “This new biological control concept was developed with the aim of preventing the increase in the population of this pest in places such as abandoned orchards, farms, farms and urban areas where there are citrus and myrtle plants, helping to prevent the migration of the plant vector insect without management for commercial orchards”, says the researcher.
It is worth explaining that management with Tamarixia radiata cannot occur in areas with chemical control, as it is susceptible to the use of pesticides. Therefore, the strategy is to use it in external areas where this care is not taken. The frequency of releases is linked to the psyllid population in the area, climate and time of year.
“The wasps can feed on 1st instar [first stage of development] psyllid eggs and nymphs and parasitize nymphs from the 3rd to 5th instars. A female T. radiata can parasitize up to 300 nymphs and the joint action between predation and parasitism can eliminate up to 500 nymphs”, says Miranda. “Biological control is a complementary and sustainable alternative for controlling greening, which does not cause any ecological imbalance, since the wasp does not act on other species of insects or plants”, she adds.
Studies by Fundecitrus and Esalq/USP have already shown that the wasp can parasitize up to 75% of psyllid nymphs, and recent work by Fundecitrus has demonstrated that the correct number of wasps to be released per hectare is 3.200 insects. In areas where there are not many plants together (such as farms and backyards), management is carried out per plant, with the release of up to 60 wasps.
The first laboratory for creating wasps emerged in 2005, within Esalq/USP, for studies and dissemination of knowledge. In 2015, a partnership between Bayer's agricultural division and Fundecitrus led to the installation of a new laboratory, with the capacity to raise 100 wasps per month, which enabled the improvement of techniques for their multiplication.
“Today, we have materials and booklets to help producers who are interested in doing this. But anyone who thinks it is something easy is mistaken, as the insect is extremely difficult to breed. To do this, we need to produce myrtle plants, create the psyllid in them, and only then produce the wasps”, says Marcelo Miranda.
According to Fábio Maia, portfolio manager for Fruits and Vegetables at Bayer, the idea of the laboratory is not to solve the problems caused by greening with wasps, but to contribute to a sustainable method of supporting external control and disseminating knowledge among interested companies and farms. in producing it.
“The decision to encourage a biofactory to produce these wasps is a collaborative process and needs to be connected to current demands. That is why Bayer has encouraged and operated through the open innovation model to establish partnerships in search of sustainable solutions to agribusiness challenges and problems. There are already some farms and cooperatives creating wasps and this is our intention: to raise the flag of sustainability, improve the model, as we are already doing, and pass it on to interested parties”, says Maia.
Fundecitrus free-releases the wasps produced in its biofactory throughout the citrus park, benefiting many citrus growers and commercial orchards.
“Orange is the third main agricultural product produced by São Paulo in terms of production value, totaling more than R$5 billion. External control is a fundamental management measure against the disease, and Tamarixia is a sustainable and innovative component within integrated greening management. Therefore, the importance of promoting sustainable solutions that can contribute to the problem”, concludes the Fundecitrus researcher.
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