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University of Gezira (2015)

Efficacy of Five Fungicides and Neem Seed Kernel Extract on the Control of Covered Kernel Smut Disease (Sporisorium sorghi (L.) Clinton) of Sorghum (Sorghum bicolor (L.) Moench)

Frah, Noraldein Suliman Nasor

Titre : Efficacy of Five Fungicides and Neem Seed Kernel Extract on the Control of Covered Kernel Smut Disease (Sporisorium sorghi (L.) Clinton) of Sorghum (Sorghum bicolor (L.) Moench)

Auteur : Frah, Noraldein Suliman Nasor

Université de soutenance : University of Gezira

Grade : Master of Science (MS) in Pesticides and Toxicology 2015

Résumé
Sorghum ranks fifth among world food cereal crops used as food, feed and for biofuel (ethanol) production. It is infected by several diseases ; the devastating one in the Sudan is the covered kernel smut (CKS), which is caused by the fungus Sporisorium sorghi. The present study was based on field observations of the high infection level of CKS in sorghum in season 2007-2008 at Hamadna Allah Block in the Blue Nile Agricultural Schemes. Farmers in that area used to grow seeds without disinfection, sometimes use expired seed dressing, or use a dose lower than the recommended. This study was an attempt to evaluate the efficacy of five synthetic fungicides and Neem seed kernel ethanolic-extract (NSK-Et.OH-extr.) for controlling covered kernel smut disease (CKS) of sorghum. Experiments were conducted both in the field (season 2008-2009) and in the laboratory. Five fungicides, viz. : Thiram® (tetramethylthiuram disulfide), and its counterpart Shiram®, Raxil® (tebuconazole), Apron Star® (thiamethoxam + mefenoxam + difenoconazole), Vincit® (Flutriafol + Thiabendazole), in addition to Neem seed kernel ethanolic-extract (NSK-Et.OH-extr.) were evaluated for inhibiting spore germination of the fungus Sporisorium sorghi in the laboratory and the field. Two susceptible varieties of sorghum, viz. Wad Ahmad and Abusabaeen were grown to investigate their performance against CKS ; RCBD was used with three replicates. The recommended dose for each product was tested together with another lower dose. NSK-Et.OH-extr. tested concentrations were 2.5%,5%, and 10%. Slide germination test (SGT) and inhibition zone techniques (IZT) were carried out in the laboratory. The recommended doses showed complete control of the pathogen on both varieties, while the reduced dose resulted in 0.72% - 1.45% disease incidence on Wad Ahmad variety, and 1.06% - 2.15% for Abusabaeen. NSK-Et.OH-extr. showed disease incidence of 10.4%, 8.28% and 5.35% on Wad Ahmad, and 9.2%, 5.19% and 1.87% for Abusabaeen in the three tested concentrations, respectively. The control results were 14.68% and 15.94% for Wad Ahmad and Abusabaeen, respectively. Laboratory tests showed no spore germination when Apron Star® and Vincit® at the concentration of 50 ppm were used, while Shiram® at the same concentration showed the highest spore germination (6.57%). Neem-extract showed 45.5% spore germination at 2,000 ppm, whereas the control exhibited 100% spore germination. Vincit® at 150 ppm showed the largest inhibition zone 41.0 mm (high efficiency) of all tested products. Inhibition zone of NSK-Et.OH-extr. for concentration of 1,000 and 2,000 ppm were 22.6 mm and 26.0 mm and for the undiluted oil (crude oil) was 40.0 mm. According to the study results, all the tested chemicals are recommended for use as seed dresser against CKS. Neem extract needs more studies to select the appropriate concentration for the control of the fungus Sporisorum sorghi without affecting sorghum seeds viability

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