Incidence of Leaf Blight Disease of Mulberry Plant and Assessment of Changes in Amino Acids and Photosynthetic Pigments of Infected Leaf

A discussion on disease severity index values. Part I: warning on inherent errors and suggestions to maximise accuracy

“…Here, we define a ‘quantitative’ ordinal scale as one that comprises a number of categories of known, specified ranges of numeric values, as described by Hartung & Piepho () – for plant disease assessment purposes these ordinal scales are generally based on the percent ratio scale relating to area with symptoms, including the Horsfall–Barratt (H–B) scale (Horsfall & Barratt, ). But other scales subdividing the percent scale into different sized intervals designated by continuous numbers might also be used (Horsfall & Heuberger, ; Hunter & Roberts, ; Hunter, ; Stovold & Smith, ; Salamati & Tronsmo, ; Kolkman & Kelly, ; Koitabashi, ; Kora et al ., ; Lazarovits et al ., ; Nitzan et al ., ; Ghose et al ., ; Vieira et al ., , ). Because of resolution, precise data on the 0–100% scale are almost always going to be more informative compared with that from an ordinal scale (Hartung & Piepho, ), but the latter has the advantage of being easier for raters to learn, and quicker and cheaper to implement.…”

“…Thus, the requirement to convert each grade measurement back to a percentage (thereby reasserting heterogeneity of variance) was necessary’. Although the procedure of calculating a DSI has been applied quite widely in studies assessing disease severity (Chester, ; Hunter & Roberts, ; Hunter, ; Kobriger & Hagedorn, ; Chaube & Singh, ; Stovold & Smith, ; Salamati & Tronsmo, ; Kolkman & Kelly, ; Koitabashi, ; Kora et al ., ; Lazarovits et al ., ; Nitzan et al ., ; Ghose et al ., ; Vieira et al ., , ; Gafni et al ., ), there have been no studies that have addressed the impact of converting data to a DSI, and the effects of the process on the accuracy of the mean value resulting from applying different methods of calculation for the DSI based on ordinal scale data.…”

“…The disease severity index (DSI), or disease index (DI), is a single index number for summarising a large amount of information on disease severity (Chester, ; Chaube & Singh, ). Disease severity indices might be used to indicate the performance of a cultivar in regard to disease resistance at one location under a given set of conditions, to determine the effectiveness of fungicides or to compare other treatments for disease control (Hunter & Roberts, ; Kobriger & Hagedorn, ; Kolkman & Kelly, ; Koitabashi, ; Kora et al ., ; Ghose et al ., ; Nsabiyera et al ., ; Gafni et al ., ). Thus, DSIs have been widely used in studies in the fields of plant pathology and plant breeding.…”

Effect of Various Factors on the Development of Leaf Spot Disease in Mulberry

“…Feeding of the diseased leaves affects the health of the silkworm adversely and cocoon yield in terms of quality and quantity (Datta, 2010). The lack of regular and systematic studies on the leaf spot disease and epidemics is responsible for the loss in leaf yield (Ghoes et al, 2010).…”

“…Among them leaf spot disease due to Cercospora moricola Cooke is the most serious disease during the month of July to September in Bangladesh (Ghoes et al, 2010). Severe defoliation and most of the commercial varieties are reported to be susceptible to this disease (Sikder and Krisnaswami, 1980).…”