Potential for application time of Pseudomonas fluorescens SP007s and biofertilizer for Alternaria leaf spot management of Chinese Kale

Application timing of Pseudomonas fluorescens SPOO7s based on plant growth stage of planting date, seedling development, and leaf stage with seed treatment, and two (at 17 and 31-day-old plants) and three-foliar spray intervals (at 14, 28 and 42-day-old plants) were evaluated in natural endemicity of commercial Chinese kale field at Suphanburi [Thailand] with a history of Alternaria leaf spot caused by A. brassicae. The effect of 1 x 10 sup 6 cfu/ml P. fluorescens SP007s in either formulations of 6-month shelf life powder or its pure culture suspension, and with or without algae biofertilizer (Goemar BM86) combined foliar spray intervals compared with conventional grower and all alone synthetic chemical plots, were also determined. Alternaria leaf spot incidence and severity were assessed every week, growth promotion and total yield were assessed, and plant growth promotion and total yield were recorded at seedling development and harvesting time, respectively. The experiment was laid out during March-May, 2008 as RCBD [randomized complete block design] of total 13 treatments in 3 x 7 in plot size with 3 replications. All treatments applied with SP007s provided significant disease reduction and yield increase better than conventional grower and alone synthetic chemical plots under 19-21% trace level of natural disease endemic (P=0.05). Overall, the application timing of SP007s with two- or three-foliar spray intervals, a combination of SP007s and algae biofertilizer foliar spray or SP007s alone, and SP007s powder formulation on its pure culture suspension had no significant effect on total yield obtained although there were treatment differences in the promoting of plant growth at seedling development and incidence of alternaria leaf spot of Chinese kale. These findings suggest the importance of disease trace level and timing for application that naturally occurring product like SP007s could be used successfully to reduce synthetic chemical use on Chinese kale.