Half of the citrus park has a high incidence of greening

The regions of Limeira – the birthplace of oranges in São Paulo –, Brotas and Porto Ferreira, located in the center-south of the state, have very high incidences of greening, the most worrying disease in the global citrus industry today, according to an annual survey carried out by Fundecitrus – Citrus Defense Fund.

While the average in the citrus park is 22,37%, in Limeira the disease already affects 61,75% of the plants; in Brotas, 50,40%; and in Porto Ferreira, 37,84%. In the regions of Avaré and Duartina, in the southwest of the state, incidences are considered high, 29,41% and 26,15%, respectively. These five regions bring together 51% of the orange trees in the citrus belt of São Paulo and Triângulo/Southwest Minas Gerais, the main orange and orange juice producing area in the world.

Loss of plants, decline and deterioration in fruit quality and contamination of young orchards

The strong presence of the disease is reflected in damage to production and harm to citrus growers: of the approximately 8,5 million plants eliminated in 2020 due to greening throughout the park, 92% were in these five regions. Other negative impacts are the reduction in production due to the premature fall of fruits and the worsening of their quality.

“In places that have low greening rates, the disease's participation in the fruit drop rate is less than 2%”, points out Fundecitrus researcher Renato Bassanezi. “However, in these regions, the disease already has a very significant participation, having been responsible for 46,7% of fruit loss in Limeira, 39% in Brotas, 30,4% in Porto Ferreira, 24,3% in Duartina and 7,8% in Avaré”, he details.

The most worrying thing is that high incidences of greening also make control difficult in young orchards, which represent the continuity of the culture – a significant part of the orange trees up to five years old planted in these regions are already sick: 32% in Limeira, 27,9% in Brotas , 18,7% in Porto Ferreira, 11,6% in Avaré and 6,1% in Duartina, while in the other regions of the belt the percentage does not exceed 10%.

The researcher explains that young plants are more susceptible to new infections because they sprout frequently and that when there are many sick adult plants and insufficient control of the psyllid [greening vector insect] it becomes more difficult to prevent the disease from spreading to new plantings. 

“The situation is even more serious, however, due to the large number of young plants present in these five regions: they account for 50,8% of orchards up to five years old”, points out Bassanezi. “In regions or locations with high incidence, the success of orchard renewal and its future are at risk if all management measures are not adopted,” she says.

Strict control inside and outside the properties

To change the scenario, the general manager of Fundecitrus, Juliano Ayres, draws attention to the need to intensify management actions, in and around the properties.

Internally, increase the rigor in controlling the psyllid and eliminating diseased plants, since, as there is no cure for contaminated trees, maintenance increases dependence on chemical control of the insect vector.

Nearby, it is also necessary to adopt greater rigor in replacing citrus and myrtle plants in backyards and eliminating poorly managed or abandoned orchards – when this is not possible, carry out psyllid control.

“The moment is worrying and requires radical decision-making by the sector to reverse the situation. The only alternative is for citrus growers to adopt management in an integrated manner and with extreme rigor”, points out Ayres.

In the regions of Limeira, Brotas, Porto Ferreira, Avaré and Duartina, where high or very high incidences of greening represent a great risk of contamination of new plantings, the advice is to avoid them or pay attention to the surroundings, looking for isolated places or with neighbors that really adopt strict management of the disease and the vector, as the insect can migrate and compromise internal management.

“Often, in high-risk situations, the best strategy is to postpone planting and adopt a 'sanitary void', that is, wait for the elimination of contaminated orchards and, consequently, the reduction of the disease's inoculum sources before planting again. ,” says Ayres. “This strategy was adopted in the Matão region in the recent past and it worked. It is an example to be followed in critical circumstances”, he adds.

The Matão region, in the center of the state, is where greening was identified for the first time in Brazil, in 2004. Despite already having high rates, the disease has been declining in recent years (9,77%).

“Internal and external management actions have proven to be effective and highly cost-effective. They have already led to a reduction in greening on farms in several regions of the citrus belt, including where the climate is highly favorable to the disease”, says researcher Renato Bassanezi. “The decrease in greening rates is directly linked to citrus growers’ adherence to really rigorous management,” he states.