Phytosanitary management of bacterial (Ralstonia solanacearum E.F. Smith) wilt of tomato (Lycopersicon esculentum Mill)

Abstract

The research was carried out from February to October 2015 in the nursery of the Faculty of Agronomic Sciences of the University of El Salvador, at 700 meters above sea level, between 13°43’6”N, 89°12’11”W, annual precipitation of 1751 mm and mean annual temperature of 23.1°C. The study comprised two phases: The first consisted of the collection of diseased tissue, isolation and identification of the bacterium Ralstonia solanacearum E.F. Smith. Sodium hypochlorite was evaluated in vitro, to determine the minimum inhibitory dose for the development of R. solanacearum E.F. Smith. The second phase began with inoculation of 200 ml of bacterial suspension (3x108 cfu/ml) per individual 22.5 lb bag containing soil. The experimental design was completely randomized, with nine treatments and ten repetitions. The treatments applied were 0.25% sodium hypochlorite, bocashi, mountain microorganisms in liquid phase (MML), soil solarization, salicylic acid, ash, and Trichoderma harzianum. The controls were: relative (Agri-Gent® antibiotic) and absolute (no control). The tomato plants were transplanted 15 days after applying the treatments. The effect of treatments, as well as the incidence and severity of the wilt were recorded beginning one week after transplantation until the ninth week. The incidence of the wilt was used to calculate the area under the disease progress curve (AUDPC) and the severity to observe the effect of the treatment on the development of the disease in the plant. The AUDPCs’ were statistically similar to the relative treatment (Agri-Gent®), according to Dunnett’s test (5%), excepting for the MML treatment. The ash treatment (4 ounces of ash per plant) was the most efficient treatment for controlling the incidence of wilt (90% effectiveness) and the severity (0.4 scale) of the disease. The results of this investigation show that there are alternative treatments to the use of antibiotics for the control of bacterial wilt in tomato, equal to or better, in economic and ecological terms.