Abstract
<title>Abstract</title> <p> Background. Verticillium wilt, caused by <italic>Verticillium dahliae</italic> Kleb., is the most destructive disease of olive orchards in the Mediterranean basin. No curative treatment is currently recognized, and management relies exclusively on preventive measures. Here we present 28 years of field data from a commercial olive orchard treated with a novel chemical formulation. Results. The orchard (cv. Picual, planted in 1994, 8 × 4 m frame, flood-irrigated) was severely affected by verticillium wilt, with 80% of trees showing partial or total wilt by 2002. A six-component chemical formulation was applied by direct tree inoculation starting in the 2006–2007 campaign on diseased trees only, and extended to all trees from 2010–2011 onward. Treatments ceased after the 2020–2021 campaign. Yield increased from a pre-treatment baseline of 292–3,765 kg/ha (mean of campaigns 1998–1999 to 2005–2006: 2,198 kg/ha) to a post-treatment maximum of 12,481 kg/ha in 2015–2016. Mean yield during the full-treatment period (2010–2011 to 2020–2021) was 6,315 kg/ha, compared to 2,198 kg/ha before treatment (2.87-fold increase). After treatment cessation, yields stabilized at 2,498–9,402 kg/ha (mean of post-treatment campaigns 2021–2022 to 2025–2026: 5,347 kg/ha), remaining substantially above pre-treatment levels. Tree ring analysis revealed up to 13 consecutive years of healthy growth following necrotic bands corresponding to the disease period. Only 0.25% of treated trees showed relapse. Adjacent untreated orchards under identical edaphoclimatic conditions display persistent damage with bare patches and repeated replanting failures. No leaf residues were detected 30 days post-treatment. Conclusions. The treatment demonstrated curative and immunizing effects against verticillium wilt in a commercial olive orchard over 28 years, with a sustained yield increase that persisted after treatment cessation. The formulation, composed of five EU-approved or inert substances plus one optional component, presents a favorable regulatory profile. Independent controlled trials are warranted to validate these findings. </p>