Evaluation of some biocontrol agents and copper compounds in controlling halo blight disease of beans caused by Pseudomonas syringae pv. phaseolicola

摘要

The present investigation was undertaken to study the effect of different antagonistic bioagents i.e. Bacillus subtilis, Pseudomonas fluorescens, Pseudomonas putida and Streptomyces aureofaciens as well as the bactericides Kocide 2000 and Tri-MiltoxFort on the incidence of halo blight disease in bean. Pot experiments were conducted in greenhouse with different cultivars of bean namely Bronco, Paulista, Narina and Nebraska. These different antagonists varied in their effects against P. syringae pv.phaseolicola of bean, the results showed that all treatments significantly reduced the blight spots on leaves of plants comparing with the check treatment. P. fluorescens and P. putida were highly effective in controlling the disease, while the moderateeffect was appeared when used B. subtilis. On the other hand, Streptomyces aureofaciens showed less effect in reducing blight spots, but it was better than control treatment. Kocide 2000 (Copper hydroxide 53.8%) at rates of 0.21%, 0.18% and 0.15% and Tri-Miltox Fort (copper sulphate oxychloride carbonate 21%) at rates of 0.28%, 0.25% and 0.22% showed significant effect on the disease severity compared with the check. The chemical compounds gave slight protection in comparison to that obtained with thebioagents. Varietal susceptibility was observed among the four varieties used, when Narina cultivar showed high susceptibility to halo blight on leaves while Paulista cultivar has a moderate susceptibility. On the other hand, Bronco and Nebraska cultivars showed less susceptibility against the disease. The disease severity on leaves decreased with the increase of plant age as a resultant of the application of antagonistic bacteria and spraying of copper compounds compared with control treatment.