Development of Rhizoctonia solani on Stems, Stolons and Tubers of Potato II. Efficacy of Chemical Applications

Abstract

Fungicide treatments have proven successful in reducing Rhizoctonia solani lesions on stems and stolons; as well as black scurf on tubers. Field studies in Parma and Aberdeen, Idaho, were conducted in 2004 and 2005 to compare the relative effectiveness of in-furrow and seed treatments for disease control on stems, stolons and tubers. The effectiveness of each fungicide placement was evaluated for control of seed-borne and soil-borne inoculum. The systemic fungicide azoxystrobin was used as the in-furrow fungicide treatment and fludioxonil was used as the seed treatment. A combination of seed treatment with an in-furrow treatment was also evaluated. All fungicide treatments had significantly lower stem and stolon disease ratings than did the non-treated control. The seed plus in-furrow treatment tended to reduce stem and stolon disease ratings more than in-furrow treatment alone. Black scurf ratings on daughter tubers were significantly reduced by fungicide applications compared to the non-treated control in two of three trials. The combination treatment had lower black scurf ratings than the in-furrow treatment alone. There were more significant differences among fungicide treatments in Rhizoctonia solani lesions on stems, stolons and tubers when seed inoculum was moderate to high compared to low seed inoculum. In-furrow treatment was relatively more effective in reducing disease on stems, stolons and tubers when soil was the primary source of inoculum, while seed treatment was relatively more effective when seed was the primary inoculum source.Resumen Los tratamientos con fungicidas han probado ser exitosos en la reducción de las lesiones en tallos y estolones por Rhizoctonia solani; así como de las costras negras en tubérculos. En 2004 y 2005 se condujeron estudios en Parma y Aberdeen, Idaho, para comparar la efectividad relativa de tratamientos a la semilla y al surco para el control de la enfermedad en tallos, estolones y tubérculos. Se evaluó la efectividad de cada colocación del fungicida para controlar el inóculo proveniente de semilla y suelo. El fungicida sistémico azoxystrobin se usó como tratamiento de fungicida al surco y fludioxonil como tratamiento a la semilla. También se evaluó un tratamiento que combinó la aplicación a la semilla y al surco. Todos los tratamientos fungicidas tuvieron niveles de enfermedad en tallo y estolón significativamente más bajos que el testigo sin tratamiento. El tratamiento a la semilla y al surco tuvo la tendencia de reducir los niveles de enfermedad en tallo y estolón más que el del surco solamente. Las categorías de la costra negra en los tubérculos hijos se redujo significativamente con las aplicaciones del fungicida en comparación con el testigo sin tratar en dos de los tres ensayos. El tratamiento combinado tuvo niveles más bajos de costra negra que el tratamiento solo al surco. Hubo más diferencias significativas entre los tratamientos de fungicidas en las lesiones de tallos, estolones y tubérculos por Rhizoctonia solani con moderado a alto inóculo en la semilla, c...

Rhizosphere Competence and Biocontrol Effect of Pseudomonas sp. RU47 Independent from Plant Species and Soil Type at the Field Scale

“…However, we found that the inoculant RU47 was not able to compensate the negative effect of the pathogen on MTY of potato. Compared to R. solani AG1-IB on lettuce which does not colonize the roots, R. solani AG3 was previously reported to affect all belowground parts of potato including the roots during the growth period ( Atkinson et al, 2011 ; Genzel et al, 2018 ). Thus, it was not surprising that R. solani AG3 had a more pronounced effect on the composition of the bacterial community in the rhizosphere of potato as indicated by the higher d- values than R. solani AG1-IB on the rhizosphere bacterial community in lettuce.…”

Foliar Application of Fungicides Registered Against Late Blight Influences Main Potato Tuber Diseases and Key Quantitative Characteristics of Tubers

“…Wilson et al (1999) reported effectiveness of seed dressing treatments on the severity of common scab using fluazinam, mancozeb and other active ingredients. Similarly, Atkinson et al (2011) verified that seed potato treatments by mancozeb combined with fludioxonil and in-furrow application of azoxystrobin are measures that significantly reduce symptoms of Rhizoctonia stem canker and black scurf. However, more reliable strategies for direct protection than the two mentioned above are currently unavailable.…”

“…The incidence and severity of black scurf were not modified. Especially mancozeb, being relatively effective against black scurf (Atkinson et al 2011), was not effective against the disease in any tested foliar applications of the five commercial fungicides in which it was an ingredient. The foliar application comes probably too late and the chemical is more dispersed in the soil in comparison with cited seed dressing treatment, which principally reduces the initial growth of the fungus by effective concentration of active ingredient.…”