Determination of the efficacies of different phosphites in the management of tomato bacterial speck disease caused by Pseudomonas syringae pv. tomato

Abstract

This study tested the efficacy of five different phosphites (calcium, copper, magnesium, potassium and zinc/manganese phosphites) and a fungicide Fosetyl-Aluminum to inhibit bacterial speck disease severity caused by Pseudomonas syringae pv. tomato (Pst) on tomato leaves. The phosphites were applied at the recommended doses to the Pst inoculated plants in pots by foliar spraying at one-week intervals for a total of 4 weeks. The plants were kept in a controlled greenhouse under relative humidity (%75-90) and temperature (22-24 °C) until disease symptoms appeared in the control plants. Phosphites and Fosetyl-Aluminum inhibited the Pst symptoms on tomato leaves by 42.1-75.0% in the first and 22.8-90.3% in the second experiments. This study demonstrated the direct influence of phosphites on tomato bacterial speck. The study suggested that phosphites can be an effective alternative for the chemical control of tomato bacterial disease. The bacterial agent, Pst, causes bacterial speck disease in tomatoes. The initial symptoms of the disease are water-soaked, small dark brown spots surrounded by a yellow halo on tomato leaves. Since the pathogen is seed-borne, control of the disease is difficult.