Since no cure exists for citrus greening-diseased plants, Brazilian researchers are developing ways to modify orange trees and the environment around groves to make it harder for greening-spreading psyllids to thrive.
LOCATION AND LAYOUT
The ideal grove envisioned by Fundecitrus researchers, in collaboration with the Spanish National Research Council/Polytechnic University of Valencia and Durham University (England), starts with a careful selection of the planting location. An isolated area 5 to 10 kilometers from urban areas and other citrus producers can drastically reduce psyllid populations.
The next steps are defining the layout of plots, the trap plant cultivation lines, the use of semi-dwarfing rootstocks and the cultivation of genetically modified orange trees to repel psyllid attacks.
“Biotechnology will greatly change the configuration of groves,” said Fundecitrus General Manager Juliano Ayres. “The new layout will include an attraction area, with species aimed (at keeping) psyllids away from the rest of the grove … Instead of the insect dispersing throughout the property with no control … the citrus grower will sacrifice the first meters of the grove in a planned manner.”
The new grove format will integrate a barrier planting system. All efforts will be directed at making it difficult for the insect to enter the grove. The first barrier is a “refuge and sacrifice area” formed by orange trees on vigorous rootstocks and by curry trees that attract the psyllid. “This creates favorable conditions for attracting the insect and concentrating populations, which can be eliminated by insecticide application before entering the grove,” said Fundecitrus researcher Marcelo Miranda.
The orange trees in this area will suffer from the effects of the disease. The curry trees, which are excellent hosts for the psyllids, do not multiply the bacteria that causes greening. The psyllid does not acquire the greening bacteria; therefore, psyllids that don’t die while feeding on the trap plant will not transmit the disease.
REPELLING PSYLLIDS
Biotechnology research is committed to developing a genetically modified plant for the production of peptide, a natural toxin lethal to the psyllid, thus reducing the use of insecticides. “This way, in the future, we will be able to count on a plant that attracts and kills the psyllid,” said Fundecitrus researcher Nelson Wulff.
The design of the grove will be an ally in the configuration of this new format of orange tree cultivation. This will depend on the development of genetically modified orange trees capable of repelling the psyllid.
Researchers believe that combining repellency with fewer new shoots will lead to a lower incidence of greening in groves. “The new grove must be composed of repellent orange trees combined with semi-dwarfing rootstocks,” Wulff said.
The new grove format also includes the use of processed kaolin. “When applied to plants, kaolin forms a white film that may disrupt the psyllid’s ability to find the host plants, thus reducing the number of adult insects landing on them. In addition, kaolin can further reduce psyllid feeding and oviposition,” said Miranda.
Learn more about the ideal grove of the future in Fundecitrus’ Citricultor magazine – Number 60.
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