Climate-driven disease puts Brazil’s citrus production at risk

Brazilian citrus growers are increasingly worried about the spread of branch rot, also known as peduncular rot or branch gummosis. This disease has become more common due to high temperatures, prolonged drought, and stress from other infections like greening, according to Brazilian media.

The rot is caused by fungi from the Botryosphaeriaceae family, particularly Lasiodiplodia and Dothiorella. These fungi can live quietly in the plant but become harmful when the tree is under stress, leading to rotting branches, bark cracks, and even the drying of entire crowns. Sticky gum often appears on younger branches, a defensive reaction from the plant.

Experts explain that the fungi exist in two forms — harmless inside plant tissues, or destructive when triggered by stress. Recent heatwaves and water shortages in São Paulo left citrus trees highly vulnerable. When the rains returned, the increased humidity allowed the fungi to spread, causing visible symptoms.

This pattern has been seen before, with outbreaks also common in September and October.

Proper diagnosis is essential for effective control. Managing branch rot requires a mix of cultural practices, stress reduction (such as shading trees), and targeted chemical or biological treatments. Keeping other diseases in check is equally important.

Although research under Brazilian conditions is limited, fungicides like triazoles, strobilurins, carboxamides, and some multisite products have shown success in other crops. Preventive treatment is especially important during stressful periods followed by rain.

A citrus research group in Brazil is now studying which species of these fungi are present in local orchards. They are also investigating how branch rot relates to other stress factors, including greening, and are testing the effectiveness of various treatments under regional conditions.

source: citrusindustry.net

photo: cropscience.bayer.co