Evaluation of a proprietary plant extract to suppress bacterial canker and improve yield in hydroponic tomatoes

Abstract

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 (OMRI)-listed proprietary blend of plant extracts, in suppressing bacterial canker and improving yield and shelf life in hydroponic tomato trials over two 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 bi-weekly, but not weekly, with AOMMA-Agro than non-treated, non-inoculated plants in one of two trials. Similar results were observed in C. michiganensis incidence determined using qPCR. Marketable yield was 29% and 44% higher from inoculated plants treated bi-weekly with AOMMA-Agro than from non-treated, non-inoculated 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.