BIOFUMIGATION WITH ESSENTIAL OILS FOR MANAGING BACTERIAL WILT OF SWEET PEPPERS

Abstract

Bacterial wilt of sweet pepper, caused by Ralstonia solanacearum (Rs), is an important disease in Brazil. The effectiveness of bergamot, blue gum, cinnamon, clary sage, copal, fennel, lemon, lemongrass, lemon-scented eucalyptus, mint, palmarosa and sweet orange essential oils was evaluated for disease control via biofumigation. Soil infested by Rs CGM-8 was biofumigated with all oils (0.14%, v:v) in the greenhouse, and with bergamot, sweet orange and palmarosa oils in the field for four days. Variables evaluated were: latency period (LP50), incidence, bacterial wilt index (BWI), area under the disease progress curve (AUDPC), plant development, Rs population in the soil, soil characteristics and the in vitro growth of Rs. Palmarosa, bergamot and sweet orange oils increased LP50 (15%), reduced BWI (60%) and AUDPC (64.4%), in the greenhouse. In the field, only the palmarosa oil increased LP50 (38%), reduced BWI (36%) and AUDPC (38%), and increased the number of fruits per plant. Only greenhouse soils biofumigated with bergamot and sweet orange oils presented significant high sodium levels. The in vitro growth of Rs was reduced in 66.9% by palmarosa oil. These results indicate that palmarosa essential oil is a potential alternative for the management of bacterial wilt of sweet peppers.