Postharvest diseases such as green mold (Penicillium digitatum), blue mold (P. italicum) and sour rot (Geotrichum citri-aurantii) cause heavy losses in citrus crops. These fungi thrive in warm, humid regions and have developed resistance to common fungicides such as imazalil, thiabendazole and pyrimethanil, driving up costs and raising environmental and regulatory concerns.
A new study offers hope using a simple, sustainable solution derived from agricultural waste. Researchers from institutions in Tucumán, Argentina tested a strawberry leaf aqueous extract (SLAE) against local isolates of these major citrus pathogens, including fungicide-resistant strains.
In lab tests published in the journal Horticulturae, SLAE at 0.05 grams per milliliter (g/mL) completely stopped mycelial (fungal thread) growth on agar plates for all tested pathogens after five days. At 0.1 g/mL, it fully prevented conidia (spore) germination and killed the spores within eight to 48 hours, depending on the fungus. Microscopy showed that SLAE damages fungal cell membranes and leads to cell death.
The extract worked well on both sensitive and resistant strains. In real-world tests on wounded lemons, applying SLAE significantly reduced green mold incidence (down to about 52% compared to nearly 100% in untreated fruit), though not quite as completely as the commercial fungicide imazalil.
SLAE is made from strawberry leaves — abundant waste from regional production in northwest Argentina — using a low-cost water extraction process. It offers a broad-spectrum, multi-target mode of action that lowers the risk of resistance development compared to single-site synthetic fungicides.
As consumer demand grows for residue-reduced and organic-friendly produce, such plant-based options help meet sustainability goals while potentially cutting reliance on restricted chemicals. This is important for growers.
The research highlights the value of turning local crop by-products into effective bio-tools. While further field optimization and formulation work are needed, SLAE shows strong potential as part of an integrated postharvest strategy.
Read the full research: “Antifungal Efficacy of Strawberry Leaf Extract and Its Effects on Conidia Cell Integrity of Postharvest Citrus Pathogens.”
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