Reduction of incidence and severity of Septoria lycopersici leaf spot of tomato with bacteria and yeasts

Septoria leaf spot, caused by Septoria lycopersici, is an important disease of tomato (Lycopersicon esculentum) which is mainly controlled by fungicide sprays. One of the alternatives to reduce fungicide applications is the use of leaf antagonists such as yeast and bacterium. This study was conducted from 1994 through 1995 in Auburn, AL, USA. The pathogen and one antagonist were isolated from field plants. In greenhouse, six yeast and one bacterial isolates were tested, in a set of seven experiments. The experiments were conducted in a completely randomized design with four to eight treatments and six replications. The antagonists (1-3 × 10(8) colony forming units ml-1) were inoculated 48h before the inoculation of the pathogen (1-2 × 10(5) conidia ml-1), under conditions of intermittent misting. The yeast isolate Y236 (Cryptococcus laurentii) and the bacterial isolate BTL (Pseudomonas putida) significantly (P <= 0.05) reduced the incidence or the severity of the disease in most experiments.