Integrated management of tomato gray mold disease using selective plant extracts and rhizobacteria

Botrytis cinerea is one of the most significant plant pathogens globally, causing extensive damage to fruits and vegetables. Botrycides remain a widely used method of plant protection; however, the introduction of plant-beneficial bacteria offers a promising and agroecologically sustainable alternative. The current study evaluated the effectiveness of plant extracts and rhizobacteria in controlling diseases caused by B. cinerea in tomatoes. Neem (Azadirachta indica), garlic (Allium sativum), and turmeric (Curcuma longa) extracts were tested alongside rhizobacterial strains (Bacillus subtilis, Pseudomonas fluorescens, and Trichoderma harzianum). In vitro experiments showed that, at a 15% extract concentration, neem and garlic inhibited fungal growth by 78% and 72%, respectively, while B. subtilis suppressed mycelial growth by 62%. Synergistic treatments, particularly neem combined with B. subtilis, exhibited the highest inhibition zone (22 mm) and an 85% synergy effect. Greenhouse trials demonstrated that neem extract combined with B. subtilis significantly reduced disease severity, achieving a disease severity index (DSI) of 1.3 and a 75% disease reduction compared to controls, which had a DSI of 4.8. Neem extract and B. subtilis alone reduced disease by 52.1% and 58.3%, respectively. The combination of neem extract and B. subtilis proved more effective in managing grey mold, promoting healthier plants, and providing a potential chemical-free alternative to fungicides. Further field trials are recommended to develop scalable, eco-friendly solutions for sustainable tomato disease management.