Alternaria sp., a new pathogen causing leaf spot in broccoli, and its management with Monarda citriodora essential oil (MEO) and isoeugenol combination

Infected leaves were collected from the field, and the causative pathogen was isolated. The pathogen was identified through morphological studies and ITS of rRNA sequencing as Alternaria sp. Monarda citriodora essential oil (MEO) and isoeugenol showed a minimum inhibitory concentration of 312.5 μg/mL and 156.25 μg/mL, respectively, against the isolated pathogen. Synergistic interaction was observed in the combination of MEO-isoeugenol with a fractional inhibitory concentration index of 0.49. The MEO-isoeugenol combination showed a significant curative and protective effect against the isolated pathogen in the glasshouse pot study.