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Effects of Rhizoctonia and Pythium spp. on Cotton Stand Establishment in Mississippi

Gabriel L. Sciumbato, Bonnie B. Cook, and J. Anna Blessitt

ABSTRACT

In 2002 and 2003, three studies were conducted at the Delta Research and Extension Center, Stoneville, MS, to compare seedling survival after inoculation with Pythium, Rhizoctonia, none, or both. These studies included the 2002 Beltwide Seed Treatment Trial, 2003 Beltwide Seed Treatment Trial, and the 2003 Cotton Extension Demonstration Trial. Significant differences were seen in all trials and varied between seed treatment. In 2002, the disease pressure was significantly higher than in 2003. Over all results, Pythium alone produced results closest to the untreated plots, indicating lower injury. Rhizoctonia and the mix of Pythium/Rhizoctonia significantly decreased stand counts. In some instances, the mix of Pythium/Rhizoctonia showed a slightly antagonistic relationship compared to Rhizoctonia alone. Rhizoctonia was the main cause of seedling disease loss. In the 2003 Cotton Extension Demonstration Trial, the lowest seedling stand counts were observed with Rhizoctonia treated plots. Those inoculated with Rhizoctonia and Pythium were similar to those inoculated with Rhizoctonia alone. Plots inoculated with Pythium alone had slightly reduced seedling stand counts over the untreated non-inoculated plots. In the 2003 Beltwide Seed Treatment Trial, the highest seedling survival for non-inoculated controls was obtained with RTU-PCNB (14.5 oz/cwt) at two weeks and with Vitavax PCNB (6.0 oz/cwt) +Allegiance (0.75/cwt) at four weeks. For Pythium infested seedlings, best stand counts were obtained from treatment with Apron XL-TL (1.0 oz/cwt) + Nu-Flow M HF (2.5 oz/cwt) + Nu-Flow ND (7.5oz/cwt) at two weeks and Dynasty (3.9 oz/cwt) at four weeks. Rhizoctonia infested seedling stand counts were highest with Apron XL-TL (1.0 oz/cwt) + Nu-Flow M HF (2.5 oz/cwt) + Nu-Flow ND (14.5 oz/cwt) at two weeks and L0020 (0.75 oz/cwt) + L0288 (0.2 oz/cwt) + L0189 (3.0 oz/cwt) at four weeks. The seedlings infested with both gave highest seedling survival with Apron XL-TL (1.0 oz/cwt) + Nu-Flow M HF (2.5oz/cwt) + Nu-Flow ND (14.5 oz/cwt) at two weeks and again at four weeks. In the 2002 Beltwide Seed Treatment Trial, the highest seedling survival for non-inoculated controls was obtained with RTU-PCNB (14.5 oz/cwt) at two weeks and with RTU Baytan Thiram (3.0 oz/cwt) + Allegiance LS (1.2 oz/cwt) + L1006 (0.6 oz/cwt) + L1080 (0.5 oz/cwt) at four weeks. For Pythium infested seedlings, best stand counts were obtained from treatment with RTU Baytan Thiram (3.0 oz/cwt) + Allegiance LS (1.2 oz/cwt) + L1006 (0.6/cwt) + L1080 (0.5 oz/cwt) at two weeks and Apron XL-TL (1.0 oz/cwt) + Nu-Coat (7.5 oz/cwt) + Weco 0257 (0.5 oz/cwt) at four weeks. Rhizoctonia infested seedling stand counts were highest with RTU Baytan Thiram (3.0 oz/cwt) + Allegiance LS (1.2 oz/cwt) + L1006 (0.6 oz/cwt) + L1080 (0.5 oz/cwt) at two weeks and four weeks. The seedlings infested with both gave highest seedling survival with RTU Baytan Thiram (3.0 oz/cwt) + Allegiance LS (1.2 oz/cwt) + L1006 (0.6 oz/cwt) + L1080 (0.5 oz/cwt) at two weeks and again at four weeks. All data was combined on inoculation type. The results showed no significant differences between the Rhizoctonia inoculation and inoculation with the Pythium-Rhizoctonia mixture. These two treatments had the most depressed seedling counts overall. The Pythium inoculation showed slight depression in stand counts over the non-inoculated group.





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Document last modified 04/27/04