Gray mold disease caused by Botrytis cinerea is an important postharvest disease of cucumber and many other
horticultural products. Effectiveness of acetic acid, two essential oils (thyme and clove) and two species of Trichoderma
(T. harzianum and T. viride) against gray mold fungus, Botrytis cinerea infected cucumber fruits, were evaluated under
laboratory conditions. Five isolates of B. cinerea were isolated from 85 cucumber samples collected from local markets of
Jazan governorate. Only B. cinerea 4th isolate was the most virulent than the other isolates. Treatments with 7.5 % of
acetic acid, 500 μl/ml of either clove and thyme essential oils and 108 spores/ml of T. harzianum showed the most
significant inhibitions (65.6- 83.3%) on B. cinerea 4th isolate growth. Also, same treatments under artificial infection
resulted in the most significant reductions in gray mold disease severity of tested cucumber fruits comparing with other
treatments as well as check treatment. All treatments resulted in conspicuous decrease in the activity of peroxidase
enzyme and affected negatively on activity of polyphenoloxidase enzyme. Obtained results, lead to suggest that
application of acetic acid, T. harzianum or essential oils are considered an applicable, safe and cost-effective method for
controlling grey mould disease on cucumber fruits.