A Brazilian study has shown that planting citrus plots parallel to the property boundary reduced HLB-spreading psyllids 12% to 23% compared to plots planted perpendicular to the property boundary. Fundecitrus conducted the study. The São Paulo Research Foundation co-financed it in partnership with Embrapa.
Another study conclusion is related to the impact of planting density on border plots. Fundecitrus researcher Renato Bassanezi and Embrapa Cassava and Fruits researcher Eduardo Girardi observed that higher plant density results in a lower proportional incidence of HLB (percentage of infected plants). However, the absolute number of diseased plants remained similar between the different densities. This suggests that increasing density may be an interesting strategy to reduce production losses, as more healthy plants remain available to compensate for the loss of some infected ones.
According to Bassanezi, the study was based on two main hypotheses. In the case of planting direction, the study investigated whether planting parallel or perpendicular to the orchard boundary would influence the barrier against psyllids.
“Our hypothesis was that plants placed parallel would close together more quickly, making it difficult for insects to penetrate,” said Bassanezi. “And indeed, after a few years, we observed a reduction in the incidence of diseased plants in parallel plots compared to perpendicular ones.”
In relation to planting density, the objective was to test whether density would influence the entry of psyllids into the plots. Bassanezi explained that plots with greater density, despite having the same number of infected plants in absolute numbers, have a lower proportional incidence.
“This occurs because the number of healthy plants dilutes the percentage of infected plants, which reduces the economic and productive impact of the disease,” Bassanezi said. “Furthermore, with greater density, the loss of production per hectare is smaller, since there are more plants to compensate for those that need to be eliminated.”
Still, Bassanezi emphasized that HLB control requires multiple strategies, including integrated management and vector control.
“Higher density or planting direction are just complementary tools,” Bassanezi said. “Success in HLB management depends on well-coordinated practices to prevent contamination from outside the orchard from reaching high levels.”
Source: Fundecitrus
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