Increased incidence of greening in Brazilian citrus farming worries producers

The annual survey of the incidence of greening (huanglongbing/HLB), produced by Fundecitrus, indicates that the disease rose from 38,06% in 2023 to 44,35% in 2024 throughout the citrus belt of São Paulo and Triângulo/Sudoeste Mineiro. This is the seventh consecutive year of growth of the worst disease in the world's citrus industry. The incidence corresponds to approximately 90,36 million trees affected. In total, there are 203,74 million orange trees throughout the citrus park. 

The advance of the disease is a reflection of the highest historical population record of the insect that transmits the disease that occurred in 2023, when the average capture per trap increased by 54% compared to 2022. On the other hand, even with the increase, the increase of 6,29 percentage points in incidence this year was significantly lower than the increase of 13,66 points from 2022 to 2023. 

According to the survey, this is a good indication that the disease is slowing down, but the scenario is still cause for concern and continues to require citrus growers to adopt effective measures to mitigate the disease in their orchards, especially with adequate control of the psyllid and elimination of diseased plants. “The advance of greening has been a reality in our citrus park for seven years. That has not changed! Citrus growers and professionals in the sector, who work in the orchards on a daily basis, need to continue the work that has been done to mitigate the disease and effectively control the psyllid. In this battle against the worst disease in citrus farming, there is no room for relaxation. All guidelines offered by Fundecitrus must continue to be implemented throughout the belt,” says Fundecitrus general manager Juliano Ayres. 

Related factors 

One of the possible factors related to the slowdown in the disease's progression from one year to the next is that for much of the second half of 2023 and early 2024, temperatures were higher than normal throughout the citrus belt. In the North and Northwest regions, where the disease was at a low incidence in 2023, a greater number of days were recorded in which maximum temperatures were above 35 °C. For Fundecitrus researcher Renato Bassanezi, this may have discouraged the occurrence of new infections. 

“Although these heat waves were not enough to reduce the psyllid population, they may have accelerated the growth of the buds and affected the multiplication of the bacteria in them, negatively interfering with the acquisition and transmission of the bacteria by the psyllid,” he explains. 

In addition to these factors, improvement actions recommended by Fundecitrus and put into practice by citrus growers in psyllid control measures were also observed. These observed practices are related to the use of more efficient products, adoption of rotation of insecticides with different modes of action, reduction of the application interval and better spraying quality, adopted with the same rigor in both young and adult groves.

The elimination of diseased plants in regions with low incidence of the disease was also maintained, and the elimination of severely affected orchards was increased. In addition, the selection of the planting area for new orchards, with the aim of finding places where disease pressure is low, favored the reduction of the incidence of the disease in the belt. 

Regions 

Of the 12 regions in the citrus belt, five have an incidence above 60%, two have an incidence between 40 and 50%, three have an incidence between 15 and 25% and only two have an incidence below 5%. The regions with the highest incidence in 2024 continue to be Limeira (79,38%), Brotas (77,06%), Porto Ferreira (71,77%), Duartina (63,93%) and Avaré (63,41%). The Altinópolis region remained in the group with a high incidence of greening (42,93%), closely followed by the Bebedouro region (39,17%), which was the region with the highest growth in percentage points. 

The regions of Matão (18,91%), São José do Rio Preto (17,57%) and Itapetininga (15,19%) remain in an intermediate range. The regions of Votuporanga (3,14%) and Triângulo Mineiro (0,11%) continue to have the lowest incidences. However, in Votuporanga, a significant increase in the disease was observed in relation to the previous year (77,4%), while in Triângulo Mineiro a reduction in incidence was observed (68,6%). 

The battle cannot stop 

Fundecitrus recommends that greening management be adjusted according to the incidence of the disease in the region where the property is located. In regions and properties with a higher incidence of the disease, it is recommended to intensify greening control measures within commercial orchards. “It is essential to maintain strict control of the psyllid, with quality applications, with a maximum interval between applications of 10 days, and rotating effective insecticides so that diseased plants do not serve as a source of inoculum and accelerate the spread and severity of the disease within the orchard and in neighboring orchards, anticipating the loss of productive longevity of the orchards”, reinforces Bassanezi. 

In regions and properties with low incidence of greening, it is essential to continue eliminating diseased plants within the orchard, in addition to measures to control psyllids and reduce external sources of inoculum. “It is highly recommended that before new planting, external actions to eliminate diseased plants in neighboring orchards, rural and urban backyards and pastures are carried out, within a radius of up to 5 km around the property, in partnership with Fundecitrus. The more isolated the property, the lower the risks will be”, he concludes.