Advanced Nanoencapsulated Essential Oil Materials as Novel Antimicrobials for the Control of Fire Blight in Apple

Fire blight, caused by Erwinia amylovora, can cause yield losses of up to 95% in apple and pear orchards. Management commonly relies on antibiotic applications during bloom, which may promote antibiotic resistance. Here, bentonite nanoclay (BNT) composites loaded with clove, thymol, or oregano essential oils (EOs) were evaluated as antibiotic-free materials for fire blight control. In vitro assays showed that BNT-EO formulations inhibited E. amylovora growth, with the minimum inhibitory concentration (MIC) of oregano EO and BNT-oregano (O) estimated at 5 g·L-1. Field trials showed that BNT-EO formulations reduced pathogen populations and flower infection over two seasons. In 2023, BNT-O achieved 76% disease reduction, approaching streptomycin efficacy (81%), although efficacy declined in 2024. Elemental analysis confirmed significant enrichment of BNT-derived Al, Na, and Si on BNT-O-treated flowers 9 days postapplication (p < 0.001). These findings support EO-loaded nanoclays as promising delivery systems for sustainable fire blight management.