Abstract
Background: Blast is a devastating disease in rice production. The current research tested the efficacy of biologicals and fungicides against blast. Aqueous extracts of Azadirachta indica, Ocimum basalicum, Cymbopogan flexousus, Thymus vulgaris, Aloe vera, Tagetes patula, Cordia curassavica, Aegle marmelos, Allium fistulosum, Syzygium aromaticum, and Calotropis gigantea were tested in vitro at 5, 10, and 15% concentrations against Magnaporthe oryzae. Also, two isolates, Bacillus cereus OG2L and B. subtilis OG2A, and one isolate, Azotobacter SAG19, and, similarly, five new generation fungicides were evaluated at three different doses against blast pathogen M. oryzae in vitro. The treatments that exhibited the best performance in vitro were further evaluated against blast disease under field conditions.Results: Extracts of T. patula (5%), C. gigantea (5%), C. curassavica (10%), A. fistulosum (10%), and A. marmelos (15%) showed greater than 81% inhibition to M. oryzae in vitro. Likewise, all three biocontrol agents, viz. B. cereus OG2L, B. subtilis OG2A, and Azotobacter SAG19, demonstrated more than 50% inhibition of mycelial growth of pathogen in vitro, and the commercial formulations of fungicides Propineb, Trifloxystrobin+Tebuconazole, Tebuconazol+Triadimenol, Bacillus subtilis Strain QST 713, and Cinnamon Oil 8%+Clove Oil 2% also significantly inhibited M. oryzae. Under field conditions, C. curassavica (10%), A. marmelos (15%), C. gigantea (5%); B.cereus OG2L; B.subtilis OG2A; Proineb and Trifloxystrobin+Tebuconazole were effective in reducing disease in addition to yield enhancement.Conclusion: Overall, the plant extracts (C. curassavica at 10%, A. marmelos at 15%, C. gigantea at 5%); bio-agents (B. cereus OG2L, B. subtilis OG2A both at 2g/l), and new generation fungicides Antracol 70WP (Proineb) at 2.5 g/l and Nativo 75 WG (Trifloxystrobin+Tebuconazole) at 0.5 g/l provided effective control against blast disease and superior plant growth and yield compared with other treatments and untreated control.
Highlights
Blast is a devastating disease in rice production
The testing of B. cereus OG2L, B. subtilis OG2A, and Azotobacter SAG19 exhibited more than 50% inhibition to mycelial growth of M. oryzae over control in vitro (Figure 1)
The application of plant extracts, viz. black sage at 10%, bael extract at 15%, and madar plant at 5%, demonstrated superior blast disease control, higher plant growth, and grain yield compared with untreated control in two field trials
Summary
Blast is a devastating disease in rice production. Blast disease is a serious constraint in rice production at the global level (Swodesh and Yuvraj, 2020; Simkhada and Thapa, 2021). It has been reported from more than 80 countries worldwide (Ou, 1985; CABI, 2018). Roy-Barman and Chattoo (2005) state that blast disease is capable of inflicting loss in rice production equivalent to feeding more than “60 million people” annually. The use of resistance and agrochemicals have been employed as strategies for the management of blast disease over 50 years. Farmers certainly need alternative management strategies to combat blast disease in the event of the breakdown of resistance
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