Effect of alternative strategies for the disinfection of tomato seed infected with bacterial canker (Clavibacter michiganensis subsp michiganensis)

Currently there is a lack of effective seed treatments for bacterial pathogens, with Cu-based compounds (the only chemical treatments permitted under organic farming standards) only providing partial control. The aim of this study was to quantify the effect of alternative treatments for the control of bacterial canker (Clayibacter michiganensis subsp. michiganensis), a major seed-borne bacterial disease in tomato. Treatments assessed were acidified nitrite (a treatment previously shown to control the seed-borne fungal disease Didymella lycopersici), antagonistic strains of Bacillus spp. and compost extracts, which were not previously evaluated as treatments for seed-borne diseases. Efficacy of treatments was determined in a seed disinfection assay. Ten-minute immersion of seed in 300 mmol l(-1) acidified nitrite resulted in 98% being pathogen free. Copper hydroxide, certain strains of Bacillus spp. and all compost extracts resulted in 100% pathogen free seed. (C) 2011 Royal Netherlands Society for Agricultural Sciences. Published by Elsevier B.V. All rights reserved.