Damping-off and root-rot diseases in bean caused by Rhizoctonia solani Kuhn are considered the most destructive diseases. Rhizoctonia solani isolates were pathogenic and varied in their virulence on bean plants (Nebraska cv.) in vivo. The isolate No. 7 of R. solani obtained from Sakha was the most aggressive one, which gave the highest percentages of pre-and post-emergence damping-off (66.7 and 26.7%), respectively. All Bioagents viz. Trichoderma harzianum, T. aureoviride, Bacillus subtilis and B. amyloliquefaciens, plant extracts of garlic, onion and neem, biocides viz. Bio-Arc and Bio-Zeid in addition to chemical fungicide (Rizolex-T as positive control) were evaluated against bean damping-off and root-rot diseases in vitro and in vivo. All tested antagonistic fungal and bacterial bioagents and plant extracts at different concentrations significantly reduced the linear growth of R. solani in vitro and decreased the incidence of R. solani damping-off and root-rot diseases under greenhouse and field conditions. Trichoderma harzianum, T. aureoviride and B. subtilis were the most effective bio-agent, while garlic and onion at 5 and 7% concentration were the most effective plant extracts against damping-off and root-rot diseases meanwhile, B. amyloliquefaciens and neem extract were the lowest effective treatments compared to the control treatment. Under field conditions during the 2019 and 2020 growing seasons, all tested treatments significantly reduced damping-off, root-rot diseases and increased the percentage of survived plants as well as improved bean plant growth parameters (plant height, number of branches/plant), yield and yield components (No. of pods/plant, weight of pods/plant and 100 seed weight) compared to the control treatment. Also, the effects of antagonistic bioagents, plant extracts at 5%, biocides and chemical fungicide on the activity of lytic enzymes (β-1,3-glucanase and protease) and oxidative enzymes (peroxidase and polyphenoloxidase) were determined in the leaves of bean plant.
One of the important Integrated Pest Management Strategies (IPM) against economic pests in Egypt is the use of biological control methods.The use of entomopathogenic bacteria is one of these methods. The authors achieved four isolates of bacteria from the naturally infected P. gossypiella in cotton fields at Assuit and Kafr El-Sheikh Governorates, Egypt. Isolates were characterized based on morphological properties. Morphological analyses were carried out based on Bergey's Manual of Systematic Bacteriology. The identification of the isolated bacteria was confirmed by using Biolog-System as, Staphyloccus sciuri, Micrococcus luteus, Brevibacterium lines & Brevibacterium casei. In addition, their larvicidal effect was evaluated. The results revealed that, S. sciuri and M. luteus were the most effective against 1 st instar larvae of PBW. Furthermore, their latent effect caused the lowest pupation % resulted from treated PBW larvae. S. sciuri was the most promising bacterial isolate to be developed as a biological control agent against P.gossypiella. The antagonists of bacterial strain against the mycelial growth of the pathogenic fungi (Rhizoctonia solani, Fusarium solani and Macrophomia phaseolina), was experimently tested to evaluate growth reduction of all pathogenic fungi.
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