Analysis of Epidemics of Rhizoctonia Aerial Blight of Soybean in Louisiana

Yang, Xiang

doi:10.1094/phyto-80-386

Cited by 25 publications

(23 citation statements)

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“…Belmar et al ., 1987). As in other Rhizoctonia diseases (such as soybean web blight; Yang et al ., 1990), the nature of the primary inoculum sources in sheath blight, and their relative importance, need confirmation.…”

Section: Discussionmentioning

confidence: 99%

“…However, several diseases caused by Rhizoctonia solani primarily affect the above‐ground parts of their host plants (e.g. Yang et al ., 1990; Sneh et al ., 1996). In the case of rice sheath blight two pathozones can be distinguished (Savary et al ., 1997): (i) the base of the plants, and (ii) the sheaths and leaves of the upper part of the plant canopy.…”

Section: Introductionmentioning

confidence: 99%

“…This first phase may be considered monocyclic (Savary et al ., 1997). When primary infections are established at the base of the crop canopy, a ‘leafborne’ (Yang et al , 1990; Savary et al , 1995), polycyclic phase can then develop and superimpose itself on the first (Savary et al , 1997) in the second pathozone, that is, the upper part of the canopy. The primary lesions expand and often coalesce, and give rise to strands of mycelium that run on the surface of healthy sheaths and leaves where they establish new lesions.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the spatiotemporal structure of rice sheath blight epidemics in a farmer's field

2001

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The spatiotemporal structures of two rice sheath blight epidemics were studied during two consecutive (rainy and dry) rice cropping seasons in a farmer's field in the Philippines. The amount of primary inoculum in the soil measured at transplanting was higher during the dry than during the rainy season, and showed nonaggregated spatial patterns in both seasons. Disease incidence (percentage tillers infected per hill) was monitored at weekly intervals on a (14 £ 17) grid of rice hills 1 m apart, at the centre of adjacent, nonoverlapping elementary quadrats of 5 £ 5 hills. The rate of disease increase at the onset of the epidemics was higher in the dry than in the rainy season, but was afterwards higher in the rainy than in the dry season. A C(a) test was used to test for overdispersion, and the betabinomial parameter u was used to assess disease aggregation in quadrats consisting of one, two, four, eight and 16 elementary quadrats. Aggregation was detectable at all quadrat sizes throughout the epidemic, according to the C(a) test. u was highest at epidemic onset and at the smallest (elementary) quadrat size, indicating a very strong aggregation of disease at the individual hill scale. u increased until disease incidence reached 40%, then declined over time. u values were generally smaller in the dry season. Semivariograms for both epidemics showed strong initial discontinuities, that is, large variance of disease incidence at the elementary quadrat scale. Some aggregation in the spatial distribution of disease incidence was indicated at higher scales in the rainy season, coinciding with the highest rate of disease increase. Semivariograms did not suggest any structure in the dry season, except for one date in the early epidemic stage. Spatiotemporal autocorrelation of disease incidence at 45 days after transplanting yielded very few variables that contributed significantly to describing the disease incidence and its increase in a given hill. In the rainy season these variables were disease incidence (or increase) in the nearest sampled neighbours, and disease incidence (or increase) observed 1 week earlier in the same hill. In the dry season only disease incidence (or increase) observed 1 week earlier in the same hill was significantly correlated with the current incidence (or its increase). The development of a spatial structure in distribution of disease is hypothesized to coincide with the spread of the pathogen from one hill to another, and with the shift from monocyclic to predominantly polycyclic processes in sheath blight epidemics. These results concur with previous reports in suggesting that management of rice sheath blight should first be directed against the leafborne, polycyclic phase of epidemics, rather than their initial phase.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of the spatiotemporal structure of rice sheath blight epidemics in a farmer's field

2001

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“…In contrast, endemic pathogens may be more rapidly deployed. Rhizoctonia solani has been reported on leafy spurge in the northern Plains (5,18 (9,20) and turfgrasses (3), but foliar infection requires prolonged leaf wetness and high humidity (1,3,21). R. solani more commonly infects subterranean and soil-line plant parts (13).…”

Section: Introductionmentioning

confidence: 99%

Moisture Requirements and Host Specificity ofRhizoctonia solaniFrom Leafy Spurge (Euphorbia esula) in Nebraska

Yuen¹,

Masters²

1995

Weed technol.

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Abstract:R230, an isolate of Rhizoctonia solani anastomosis group 5 from leafy spurge, caused root and crown rots on leafy spurge when inoculated via soil in greenhouse experiments. The fungus grew through soil over a wide range of matric potentials (-0.01 to -1 MPa). When applied to leafy spurge foliage, the fungus blighted young adventitious shoots, but not mature stems. Foliar infection required high relative humidity. Mycelial growth on plant surfaces stopped at below 92% relative humidity. Pathogenicity of R230 was not limited to leafy spurge. The fungus caused stem and foliar lesions on all crops tested (alfalfa, smooth bromegrass, corn, Kentucky bluegrass, soybean, tall fescue, and wheat) when plants were kept under high humidity. It reduced seedling emergence and survival in soybean, Kentucky bluegrass, and tall fescue. R230 also caused a foliar blight on spotted spurge. The potential for R230 to damage crops will limit application of the fungus to noncultivated areas and to sites where it is endemic.

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“…Weather conditions conducive for Rhizoctonia web blight have been reported on soybean (3,28,29), maize (1), and perennial ryegrass turf (12,15). Fidanza et al (12) developed a warning m od el that used the mean daily relative humidity and minim um daily air tem perature to accumulate daily points.…”

mentioning

confidence: 99%

Weather-Based Forecasting of Rhizoctonia Web Blight Development on Container-Grown Azalea

Copes¹

2015

Plant Disease

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Copes, W. E. 2015. Weather-based forecasting of Rhizoctonia web blight development on container-grown azalea. Plant Dis. 99:100-105.The most reliable approach for timing fungicides to control Rhi zoctonia web blight on container-grown azalea has been a fixed calen dar date. The purpose of this study was to model periods when a pre ventive control could be applied in advance of significant increases in leaf blight intensity (LBI) in response to a daily accumulated risk value indicating conducive conditions of temperature (18 or more hours between 20 and 30°C when maximum temperature is less than 35°C), leaf wetness (16 or more hours), and/or rainfall (greater than 6.7 mm above the maximum daily irrigation). Analysis used weather measure ments taken every 30 minutes from 11 site-year datasets from 2006 to 2011, and weekly or biweekly LBI assessments. Six developmental site-year datasets were analyzed using receiver operating characteristic (ROC) curve procedures to evaluate models. Only a single model pre dicted true positives and negatives significantly greater than a 50:50 probability. Subsequently, five site-year validation datasets were evalu ated. Similar results were obtained from both the developmental and validation datasets, which produced ROC areas of 0.7715 (P = 0.0120) and 0.8393 (P = 0.0034), respectively. The practical application of weather-based forecasting for management of web blight in nurseries is discussed.

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Analysis of Epidemics of Rhizoctonia Aerial Blight of Soybean in Louisiana

Cited by 25 publications

References 0 publications

Analysis of the spatiotemporal structure of rice sheath blight epidemics in a farmer's field

Analysis of the spatiotemporal structure of rice sheath blight epidemics in a farmer's field

Moisture Requirements and Host Specificity ofRhizoctonia solaniFrom Leafy Spurge (Euphorbia esula) in Nebraska

Weather-Based Forecasting of Rhizoctonia Web Blight Development on Container-Grown Azalea

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