Comparison of single-point alfalfa yield models based on visual disease intensity and remote sensing assessments

Guan, Jie; Nutter, Forrest W.

doi:10.1080/07060660409507149

Cited by 11 publications

(6 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, this method proved to be noninvasive, nondestructive, and easier to perform compared with visual methods that require entering and damaging the pyrethrum canopy while attempting to follow a systematic sampling design to select and remove stems for visual assessment. Moreover, measurements of reflectance obtained from a handheld radiometer have been shown to be faster and easier to obtain than visual methods of assessment in several other pathosystems (18,24,32,34,35). In our study, we found radiometric assessment of plots to be approximately three times faster than visual disease assessments, without the need to physically remove stems for visual assessments.…”

Section: Discussionmentioning

confidence: 50%

“…However, radiometric methods do account for reductions in GLAI because there is a high correlation between percent reflectance values and GLAI. Plant growth has been demonstrated to be proportional to the amount of radiation intercepted by plant canopies, especially at crucial stages of plant development (13,17,18). Previous research on the temporal dynamics in foliar disease intensity and stem growth of the P. ligulicola-pyrethrum pathosystem indicate that August and September were the most likely critical infection period, with maximum disease intensity occurring around mid-October (36,38).…”

Section: Discussionmentioning

confidence: 99%

“…Visual disease intensity assessments are often difficult to perform and do not account for reductions in green leaf area index (GLAI) due to plant growth that is slowed or even stopped in response to disease or stress (18,23,30). However, radiometric methods do account for reductions in GLAI because there is a high correlation between percent reflectance values and GLAI.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Use of a Multispectral Radiometer for Noninvasive Assessments of Foliar Disease Caused by Ray Blight in Pyrethrum

et al. 2007

Self Cite

View full text Add to dashboard Cite

. Use of a multispectral radiometer for noninvasive assessments of foliar disease caused by ray blight in pyrethrum. Plant Dis. 91:1397-1406.Foliar disease due to ray blight (Phoma ligulicola) in pyrethrum was quantified at three locations over 2 years in Tasmania, Australia. To obtain a range of ray blight disease intensities, replicated plots were treated with fungicides that varied in efficacy to control ray blight. Visual disease assessments and measurement of canopy reflectance were made at least once during spring (September through December). Visual assessments involved removal of flowering stems at ground level from which measurements of defoliation severity and the incidence of stems with ray blight were obtained. Reflectance of sunlight from pyrethrum canopies was measured at 485, 560, 660, 830, and 1,650 nm using a handheld multispectral radiometer. Measurements from these wavelengths also were used to calculate all possible reflectance ratios, as well as four vegetative indices. Relationships between wavelength bands, reflectance ratios, vegetative indices, and disease intensity measures were described by linear regression analyses. Several wavelength bands, ratios, and vegetative indices were significantly related in a linear fashion to visual measures of disease intensity. The most consistent relationships, with high R 2 and low coefficients of variation values, varied with crop growth stage over time. The ratio 830/560 was identified as the best predictor of stem height, defoliation severity, and number of flowers produced on each stem in October. However, reflectance within the near-infrared range (830 nm) and the difference vegetative index was superior in November. The use of radiometric assessment of disease was noninvasive and provided savings in disease assessment time, which is critical where visual assessment is difficult and requires destructive sampling, as with pyrethrum.

show abstract

Section: Discussionmentioning

confidence: 50%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Use of a Multispectral Radiometer for Noninvasive Assessments of Foliar Disease Caused by Ray Blight in Pyrethrum

et al. 2007

Self Cite

View full text Add to dashboard Cite

show abstract

“…Improvements were apparent as both systematic and constant bias were reduced. regression to evaluate and compare the accuracy and precision of: (i) colour disease assessment protocols (e.g., use of a linear scale versus a logarithmic disease assessment scale) (Nutter and Esker, 2005), (ii) disease assessment instruments (e.g., image analysis or remote sensing sensors and instruments) (Nutter, 1990;Guan and Nutter, 2004), and/or (iii) disease raters, can provide researchers with statistical methods to determine the accuracy and precision of disease assessment data (Nutter et al, 1993;Nutter and Littrell, 1996;Nutter, 1997a;Guan and Nutter, 2003). Thus, researchers can and should place greater focus upon evaluating, comparing, and selecting the best disease assessment protocols, instruments, and/or raters that best meet the goals of the research.…”

Section: Discussionmentioning

confidence: 99%

Disease Assessment Concepts and the Advancements Made in Improving the Accuracy and Precision of Plant Disease Data

2006

Self Cite

View full text Add to dashboard Cite

show abstract

“…For example, assessments that will be used to quantify the relationship between disease intensity (X) and yield loss (Y) will require greater accuracy and precision than assessments used to determine the relative levels of cultivar resistance (low, moderate, high) in a plant breeding programme Guan and Nutter, 2004). In more advanced breeding lines, however, more accurate and precise information may be needed to quantify levels of rate-reducing resistance (Nutter and Gaunt, 1996;Nutter and Parker, 1997).…”

Section: Choosing a Scale Of Measurement And Types Of Scalesmentioning

confidence: 99%

The Role of Psychophysics in Phytopathology: The Weber–Fechner Law Revisited

Nutter

Esker

2006

Eur J Plant Pathol

Self Cite

View full text Add to dashboard Cite

The accuracy and precision of disease severity assessment data might be improved if there was a better understanding of how the laws of psychophysics actually relate to the theory and practice of phytopathometry. In this regard, we utilized a classical method developed in the field of psychophysics (the method of comparison stimuli) to test Horsfall and Barratt's claim that raters cannot accurately discriminate disease severity levels between 25% and 50% because, according to the Weber-Fechner law, visual acuity is proportional to the logarithm of the intensity of the stimulus. We show for two pathosystems, wheat leaf rust and grapevine downy mildew, that raters can accurately discriminate disease severity levels between 25% and 50%, and that although Weber's law appears to hold true, Fechner's law does not. Furthermore, based upon our results, the relationship between actual (true) disease severity (X) and disease severity estimated by raters (Y) is linear, not logarithmic as proposed by Horsfall and Barratt.

show abstract

Comparison of single-point alfalfa yield models based on visual disease intensity and remote sensing assessments

Cited by 11 publications

References 22 publications

Use of a Multispectral Radiometer for Noninvasive Assessments of Foliar Disease Caused by Ray Blight in Pyrethrum

Use of a Multispectral Radiometer for Noninvasive Assessments of Foliar Disease Caused by Ray Blight in Pyrethrum

Disease Assessment Concepts and the Advancements Made in Improving the Accuracy and Precision of Plant Disease Data

The Role of Psychophysics in Phytopathology: The Weber–Fechner Law Revisited

Contact Info

Product

Resources

About