Onion (Allium cepa L.) is one of the major vegetable crops in Egypt that are damaged and lost by Botrytis neck rot. The aim of this study was to determine the efficacy of silica gel, acetic acid, fulvic acid and charcoal as protective agents against Botrytis allii under both in vitro and in greenhouse and field conditions. In vitro, the maximum disease reduction was observed by 1%, 0.8% and 0.5% acetic acid (73.7%, 63.7%, and 61.2%, respectively), followed by 2% of charcoal (52%) and 3% of silica gel (47.5%). In the greenhouse and field conditions, silica gel (3%) and acetic acid (1%) were the best treatments and were shown to inhibit the disease up to 85.7% in green house and up to 70.4% and 69% in field, respectively compared to untreated control, therefore, we considered that the two treatments would be suitable applications as a safe and cheap alternative to fungicides.