Scientists have discovered that carob and pomegranate extracts may offer olive trees natural protection against anthracnose. Credit: Shutterstock

A new international study has revealed that plant extracts from carob leaves and pomegranate husks could help protect olive trees against anthracnose, one of the most destructive diseases in olive cultivation.

Anthracnose ranks among the most damaging diseases to olive trees. Often called “soapy olive” because of the fruit’s greasy appearance when infected, this condition is caused by several fungal species within the Colletotrichum genus. It can drastically cut yields and lower olive oil quality, particularly during severe outbreaks.

In a new international study, researchers have pinpointed two natural substances that may help curb the impact of this disease: plant extracts taken from carob leaves and pomegranate husks. Once considered waste from agricultural and food processing industries, these materials are now being recognized as potential eco-friendly substitutes for conventional fungicides, supporting a more sustainable biocircular economy.

The research, carried out by the Department of Agronomy at the University of Cordoba (DAUCO) in partnership with the Polytechnic Institute of Bragança (Portugal), found that both extracts greatly reduced the production and germination of the fungus’s conidia and blocked the formation of appressoria, “two key structures the fungus uses to disperse and initiate infection in the plant,” explained Begoña Antón, the study’s lead author.

Image of two of the researchers who developed the study. Credit: University of Córdoba

Furthermore, the study’s findings highlight that the preventive foliar application of both extracts—especially carob—activates the plant’s defense mechanisms linked to its antioxidant response. This application also increases the production of certain phenolic compounds that help strengthen the plant’s natural resistance to the pathogen.

A study conducted under controlled conditions that opens new doors

To achieve these results, the research team conducted in vitro tests and bioassays on both individual olives and olive seedlings in controlled environment chambers. In fact, in this latest trial, researchers confirmed that carob leaf extract can reduce the disease’s incidence by 35%.

“Although this percentage is lower than that achieved with a traditional copper-based fungicide, it represents an important step forward in optimizing the effectiveness of these compounds,” stated Carlos Agustí, the principal investigator on the study.

This study opens up new avenues for the development of sustainable anthracnose control strategies using bioprotectants, which could reduce the need for fungicides, as their use is increasingly restricted by the European Union. However, several important steps still need to be taken to achieve this, including testing how these bioprotectors perform in field conditions, where environmental and biological factors are more variable and complex, and studying the feasibility of scaling them up industrially if their effectiveness is confirmed.

Reference: “Carob and pomegranate extracts enhance plant defence mechanisms against olive anthracnose through antioxidant activity and phenolic compounds production” by Begoña I. Antón-Domínguez, Luiza Sánchez-Pereira, Sandra Lamas, Nuno Rodrigues, Paula Baptista and Carlos Agustí-Brisach, 6 August 2025, Industrial Crops and Products. DOI: 10.1016/j.indcrop.2025.121653

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