Greening advances in the citrus belt and demands effective actions from the sector to reduce incidence in orchards

The annual survey of the incidence of greening (huanglongbing/HLB) carried out by Fundecitrus indicates that the disease rose from 24,42%, in 2022, to 38,06% in 2023 throughout the citrus belt of São Paulo and Triângulo/Southwest Mineiro. A growth of 56% which corresponds to approximately 77,22 million diseased trees out of a total of 202,88 million orange trees throughout the park. The moment continues to require more effort and strategy from citrus growers to more effectively control the disease. This is the sixth consecutive year of growth in the incidence of the disease, but it was the largest increase in percentage points in the entire historical series since 0.

The incidence increased considerably in all regions and property sizes. “It is a very delicate moment. We are in a situation where correct management will be decisive in reducing the incidence”, advises the general manager of Fundecitrus, Juliano Ayres.

Regions

The regions with the highest incidence continue to be Limeira (73,87%), Brotas (68,53%), Porto Ferreira (59,65%), Duartina (55,66%) and Avaré (54,79%). However, this year the Altinópolis region became part of this group with a high incidence of greening (40,60%). Of these regions, Duartina, Altinópolis, Avaré and Brotas showed the largest increases in percentage points in relation to the 2022 incidence (30,29; 24,64; 22,99 and 19,12 points, respectively).

In the intermediate range, the regions of São José do Rio Preto (20,54%), Bebedouro (20,37%), Matão (17,42%) and Itapetininga (11,47%) remain. The considerable increase in percentage points in the regions of Bebedouro and Matão (respectively, 12,94 and 8,90) in relation to 2022 is noteworthy, as in these regions the disease was remaining stable or decreasing in the last five years. In São José do Rio Preto and Itapetininga, the increase was 6,04 and 4,32 percentage points, respectively. The regions of Votuporanga (1,77%) and Triângulo Mineiro (0,35%) remain with lower incidences, however in both regions an increase in the disease was observed (1,72 and 0,34 percentage points in Votuporanga and Frutal, respectively ).

Growth

As warned in previous reports prepared by Fundecitrus, one of the main causes of the advance of greening has been the practice of keeping sick trees in commercial orchards, especially trees in production, with insufficient control of the psyllid. “This has led, year after year, to an increase in the population of infectious psyllids also within commercial orchards and, consequently, an increase in the incidence of greening”, says Fundecitrus researcher Renato Bassanezi. In 2022, recalls the researcher, the psyllid population monitored by the Fundecitrus Phytosanitary Alert system was double the population in 2021, which had already been a record since 2009. “This record increase in the psyllid population, associated with the maintenance of diseased plants in orchards, culminated in an alarming increase in the disease in 2023”, he says.

Resistance and climate

Among the four fundamental pillars of psyllid control (use of insecticides and effective doses, rotation of insecticides with different modes of action, intervals between applications of less than or equal to 7 days during budding periods and quality applications in all parts of the plant) , what contributed most to the inefficiency of psyllid control and, consequently, to the increase in the incidence of greening, was the intensive and repeated use of insecticides from the pyrethroid and neonicotinoid groups, which showed a proven occurrence of resistant psyllids. “The lack of adequate rotation of insecticides with different modes of action, adopted by most citrus growers, led to the rapid selection of psyllid populations resistant to these two groups of insecticides and, the consequent loss of effectiveness of these products in the field", explains To reverse this situation, it is necessary to interrupt the use of these insecticides by all citrus growers in regions with control problems for at least three months and to adopt a rotation of insecticides from other chemical groups with 3 to 4 different modes of action .

The climate also helps to understand the scenario of increased incidence of the disease. In this last harvest, the climatic conditions in the extreme north and northwest regions included more frequent rains and less hot temperatures during spring and summer, favoring an increase in the psyllid and the spread of the bacteria. In the extreme south (Itapetininga region) the more frequent and abundant rains did not represent a limiting factor for the sprouts, which serve as food for the insect, nor for the multiplication of the bacteria, however the lower temperatures in autumn and winter slow down the in a certain way the development of the psyllid. In the central and southern regions, in general, rainfall was better distributed and temperatures were favorable for the psyllid and bacteria.

Cancer and CVC

The survey prepared by Fundecitrus also points to an increase in the incidence of cancer in orchards. According to the new survey, the disease is present in 19,97% of plants, an increase of 6,4% in the incidence of the disease in the São Paulo citrus park and Triângulo Mineiro compared to the previous year. The current index resumes the upward trend of the disease interrupted in 2021 due to the lack of rain.

The incidence of CVC (citrus variegated chlorosis) remains low throughout the citrus area. The percentage of plants with disease symptoms in 2023 (0,56%) was lower than that seen in 2022 (0,80%). In 2023, the incidence corresponds to approximately 1,14 million of a total of 202,88 million orange trees.