Fungitoxicity of systemic fungicides on control efficacy againts root rot and foot rot diseases (Phytophthora parasitica Dastur.) of black pepper
1994
Chawalert Treekarunasawat
The causal organism of pepper foot and root rot disease was isolated from a diseased plant and various biological properties e.g. morphology, physiology. etc. Regarding chemical control measure, various systemic fungicides were brought for evaluation on their effectiveness to control the fungal pathogen by demonstrating the ED50, slope value, and their performances when applied through drenching and spraying on diseased leaves, seedlings, cuttings and diseased plants in the field, all experimental data were analyzed through a Duncan's multiple range test methods that provided a precised explanation of the result. Experimental result indicated that the isolated fungus was catagorized as Phytophthora parasitica when grown on PDA+BNPRH which shown an irrigular rosette pattern of white cottony and fine mycelium that patially submerged into medium. Zoosposangium, 28-34 * 20-28 micro m., L-B ratio 1.31 (1.23-1.43), with papilla opening and without pedicel. Zoospore produced in zoosporangia without vesicle and released out through papilla opening. Effectiveness of fungitoxic chemicals revealed that, a laboratory result was reversed from in vivo test, ED50 of many fungicides e.g. Aliette, Foli-R-Fos 400, Tachikaren and Sandofan MZ were poor but when tested on diseased leaves, seedlings, cuttings and diseased plants provided an effective control. Infected leaf-dippings in Apron, Aliette, Sandofan MZ, dimethomorph, HALT and Tachikaren provided a complete disease control. On the otherthand, seedlings grown in P. parasitica infested soil and recieved a chemical sprays indicated that Aliette, Foil-R-Fos 400 and dimethomorph were the best fungicide to protect seedlings. The similar results also obtained from stem cuttings trials. Spray trial on diseased plants in the field revealed that, Aliette, Ridomil MZ72, dimethmorph and Terrazole were the best compounds, where as Foli-R-Fos 400, injection formular, was poor to used as spray.
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