Research indicates that nutritional and hormonal programs do not reduce the severity of greening

A three-year field study conducted in partnership with Fundecitrus compared the effect of several enhanced nutritional programs (PNA) and exogenous auxin (phytohormone) sprays on the progress of greening severity and fruit drop and production of asymptomatic and with symptoms of the disease. Furthermore, it estimated the cost-benefit ratio of the treatments.

As a result, over time, none of the evaluated programs contributed to reducing the evolution of greening severity (which increased from 10% to 60%), decreasing the percentage of fruit drop (remained above 40% on branches symptomatic) or to maintain or increase fruit production from symptomatic trees.

In this way, the best cost-benefit ratio was obtained for the citrus grower's standard nutritional program, without adding more nutrients and 2,4-D. For every R$ 1,00 spent on the producer's conventional nutritional program, there was a revenue of R$ 84,68 in production on diseased plants, while, for PNA with or without 2,4-D, the revenue varied between R$ $7,75 and R$38,02.

According to Fundecitrus researcher Renato Bassanezi, these observations indicate that PNA and 2,4-D sprays are not important in controlling greening or mitigating its damage and that their use, instead of removing diseased trees, can accumulate inoculum on the property and increase the spread of the disease throughout the region.

“The work showed that these treatments do not bring any benefit, they only increase production costs”, he comments.

Diseased trees are a source of inoculum where the psyllid can acquire the bacteria that causes greening and transmit it to a healthy tree, thus spreading the disease. “Strict control of the insect vector and the elimination of diseased plants on and off farms are still the best way to control greening in the long term,” says Bassanezi.

The guideline is that producers should be cautious when using new products that promise benefits against greening, although there is still no cure. “Before using a new product on the entire farm, the ideal is to initially test it on just one part of the plot and compare the results with the other part that did not receive the treatment to check whether there will be benefit and financial return”, says Bassanezi.

To read the article “Effect of enhanced nutritional programs and exogenous auxin spraying on huanglongbing severity, fruit drop, yield and economic profitability of orange orchards” and find out all the details of the research, access here.