Efficacy of Bacillus-fortified organic fertiliser in controlling bacterial wilt of tomato in the field

Ralstonia solanacearum (Smith) has been a severe pathogen on tomato worldwide and no effective control measure is available yet. To develop a new bio-product for controlling this disease, antagonistic Bacillus amyloliquefaciens strains QL-5 and QL-18 were isolated from rhizosphere soil of tomato and used separately or together to fortify organic fertilisers to control bacterial wilt of tomato (BWT), both in the greenhouse and in the field. The bio-organic fertiliser (BOF) fortified with a mixed inoculation of QL-5 and QL-18 effectively decreased R. solanacearum disease incidence in both greenhouse and field conditions. However, the suppressive efficacy in the field depended on the season. Disease incidence in the spring crop season in 2009 and 2010 was significantly reduced, while a low suppressive effect was observed in the autumn crop season in 2008 and 2009. The initial R. solanacearum population in the soil was nearly three times lower in the spring before transplanting seedlings than in the autumn crop season. The pathogen population in the field was positively and significantly correlated with air temperature but was not correlated with relative humidity. The interaction between BOF and other soil and climatic factors that affect pathogen density in the field should be clarified.