Rocha pear, a well-known Portuguese fruit, faces significant pre- and post-harvest challenges due to fungal infections. Stemphylium vesicarium is a phytopathogenic fungus that causes brown spot disease and has been responsible for significant economic losses. The available synthetic treatments are not fully effective and can negatively impact the environment, highlighting the need for sustainable alternatives. Several seaweeds are known for their antimicrobial properties, showing potential in this context. Pre-harvest trials investigated the effects of Fucus vesiculosus and Sargassum muticum extracts on pear trees. The seaweed extracts were applied both before and after inoculation with the pathogen S. vesicarium. The continuous application of S. muticum extract effectively prevented disease symptoms, possibly due to bioactive compounds including phytohormones, fatty acids, among others, suggesting the potential of seaweeds as natural priming agents to boost plant defenses.

Following the value-chain process of Rocha pear, post-harvest fungal infections, caused by pathogens such as Alternaria alternata, Botrytis cinerea, Fusarium oxysporum, and Penicillium expansum, also result in substantial losses, ranging from 20 to 25% of total fruit industry output. Seaweed extracts from Asparagopsis armata, Codium sp., F. vesiculosus, and S. muticum were evaluated for their antifungal properties. In vitro tests revealed that A. armata extracts strongly inhibited fungal growth, and promising in vivo results against B. cinerea were obtained using S. muticum.

These studies highlight the potential of seaweed-derived compounds in managing both pre- and post-harvest fungal diseases in Rocha pear, offering a more sustainable and ecofriendly approach to agricultural practices and fostering a bioeconomy that links the sea to the farm.