Preharvest Management Measures for the Control of Bitter Rot in Citrus

Citrus production in Uruguay is mainly oriented toward the export of fresh fruit; therefore, the competitiveness of the sector largely depends on the sanitary quality of fruit during the postharvest stage. Increasing international requirements regarding food safety and pesticide use have reduced both the number of authorized active ingredients and maximum residue limits, restricting the use of conventional fungicides. As a result, the sector currently has limited effective tools for the control of postharvest diseases, such as sour rot caused by Geotrichum citri-aurantii (G. citri-aurantii), one of the most economically important postharvest pathologies.

As an alternative, low–environmental-impact strategies have been developed; however, their effectiveness is often limited and mainly fungistatic, which hinders their use as a sole control measure. In this context, the Non-polluting Integrated Control of Postharvest Diseases (CINCEP) proposes a comprehensive approach that integrates preharvest, harvest, and postharvest factors through the combination of sustainable practices.

Within this framework, the present study evaluated two non-chemical management tools aimed at reducing G. citri-aurantii inoculum under field conditions: the use of organic mulch as a physical barrier and preharvest fruit washing to promote spore removal. The application of mulch beneath citrus trees, assessed using a randomized complete block design, resulted in a 51 % reduction in spore presence compared to the control treatment. Additionally, three independent trials evaluated the effect of preharvest washing with water or a detergent solution, showing reductions in spore abundance of 63.7 % with water and 40.5 % with a 0.05 % detergent solution, while a direct comparison between both treatments showed a 17.4 % reduction with detergent compared to water.

Overall, these results support the incorporation of organic mulch and preharvest washing with a soapy solution as complementary practices within a CINCEP program, contributing to the reduction of G. citri-aurantii abundance and promoting a more sustainable citrus production system aligned with international market requirements.