Achievement of induced systemic resistance in greenhouse cucumber against Bemisia tabaci using humic acid, salicylic acid and Trichoderma harzianum

Cucumber ( Cucumis sativus L.) is a globally significant crop, valued for both its nutritional and economic contributions. Its production, however, is heavily compromised by insect pests such as whiteflies ( Bemisia tabaci ), which cause substantial yield reductions. The overreliance on chemical pesticides raises environmental and health concerns, underscoring the need for sustainable pest management strategies. This study assessed the potential of biological and organic agents namely, Trichoderma harzianum ., humic acid, and salicylic acid in activating plant defenses and mitigating pest impacts. Multiple treatments were applied to cucumber plants, with evaluations of pest suppression, plant growth parameters, and biochemical defense responses. Results demonstrated that plants treated with T. harzianum , and organic agents exhibited a remarkable decline in pest populations. Importantly, these treatments significantly improved plant growth parameters, including plant height, stem diameter, and biomass, compared to infested but untreated plants. The application of these beneficial agents also stimulated systemic resistance, as evidenced by increased activities of antioxidant enzymes such as superoxide dismutase (SOD) up to 3.41-fold, catalase (CAT) up to 2.97-fold, peroxidase (POX) up to 3.29-fold, phenylalanine ammonia lyase (PAL) up to 2.99-fold, and polyphenol oxidase (PPO) up to 2.73-fold, alongside elevated levels of phenols and total proteins that contributed to enhanced defense capacity. Integrating T. harzianum , humic acid, and salicylic acid presents an effective, eco-friendly approach for controlling pests and promoting growth in cucumber plants. These findings emphasize the importance of biological treatments in sustainable agriculture, leading to healthier plants with improved productivity compared to those subjected only to pest attacks.