Evaluation of a Proprietary Plant Extract to Suppress Bacterial Canker and Improve Yield in Hydroponic Tomatoes

Bacterial canker of tomato, caused by the systemic bacterial phytopathogen Clavibacter michiganensis, can result in significant economic losses in hydroponic tomato production systems. Lacking effective bactericides, the disease is managed primarily by clean seed procedures, sanitation, and quarantine. Plant extracts have been shown to display antimicrobial activity and/or induce plant resistance to disease. We tested the efficacy of AOMMA-Agro, an Organic Materials Review Institute-listed proprietary blend of plant extracts, in suppressing bacterial canker and improving yield and shelf life in hydroponic tomato trials over 2 years. Experiments were conducted in a greenhouse with 'Campari' tomatoes transplanted into coconut coir blocks and grown under hydroponic conditions. Plants were trellised, pruned, and harvested according to commercial standards. AOMMA-Agro was applied weekly or biweekly as a foliar spray and inoculated with C. michiganensis. Plants treated with water and inoculated or not inoculated served as controls. Disease severity was relatively low in both years; however, disease progress was significantly lower for plants inoculated and treated biweekly, but not weekly, with AOMMA-Agro than for nontreated, noninoculated plants in one of two trials. Similar results were observed for C. michiganensis incidence determined using qPCR. Marketable yield was 29 and 44% higher from inoculated plants treated biweekly with AOMMA-Agro than from nontreated, noninoculated plants in the two experiments. These results support the use of AOMMA-Agro as a potential option for bacterial canker management and yield enhancement in hydroponic tomato greenhouse production systems.