Fundecitrus research identifies periods of greater susceptibility of fruits to early blight

From November onwards, rains are more intense and frequent in São Paulo, a time when oranges are more susceptible to early blight. To clarify how long fruits can be infected by the fungus that causes the disease, Fundecitrus, in partnership with Esalq/USP and Citrus Research International (CRI), carried out work during two harvests in orange orchards in the central region of the state.

The doctoral student at Esalq/USP, Régis Fialho, explains that, in both harvests, a sample of fruits received the fungus only in October, after the petals had fallen, and other samples received the fungus monthly until July, a period in which the fruits had already they were ripe. For control, a fruit sample did not receive the fungus and another sample received it ten times, monthly from October to July.

“The results show that the symptoms of black spot were more intense when the fungus was applied ten times to the fruits [from October to July] and when the application was made only in November or only in December, months in which the fruits were 1,5 and three centimeters in diameter, respectively, proving more susceptible to infection”, he comments.

“The fruits from January and February, with diameters between four and five centimeters, showed considerable intensity of the disease, showing that these periods also demand attention from the citrus grower in controlling the disease. The oranges that received the fungus in October, after the petals fell, in the pellet phase, or after March, with a diameter greater than six centimeters, showed fewer symptoms compared to other months”, highlights Fialho.

The research also involves quantifying the fungus in the orchard and the effect of fungicides throughout the different months of fruit development. In the next steps, climatic variables will be correlated with the susceptibility of the fruit, the quantity of the fungus and the effect of fungicides in the different months, in order to understand how the climate affects the intensity of black spot in the orchard.

For Fundecitrus researcher and research advisor Geraldo Silva Jr., the results reinforce that, from November onwards, when the rainy season usually begins, the fruits must be protected, mainly, with strobilurins.

“This group of fungicides is very efficient and provides up to 95% control while copper has, at most, 70% efficiency. Therefore, it is from the penultimate month of the year that attention must be redoubled so that early blight does not cause considerable damage to plant production,” he states.