Plant Disease (1999) 83, 186-188

R. Silva-Acuña, L.A. Maffia, L. Zambolim and R.D. Berger (1999)
Incidence-severity relationships in the pathosystem Coffea arabica-Hemileia vastatrix
Plant Disease 83 (2), 186-188
Abstract: Incidence-severity relationships for coffee rust were studied to determine if the easily assessed incidence could be used to evaluate host resistance and fungicide treatment. At two locations in each of 3 years, the incidence of rust on 300 leaves was compared with two assessments of severity: (i) the average number of sporulating pustules per leaf, and (ii) the estimated leaf area with rust. For nine or 10 assessments in time at one location and pooled over 3 years, the average number of sporulating pustules per leaf (Y(sp)) was well related with the incidence of leaves with rust (X) as Y(sp) = 0.02982+ 0.017035X +0.000573X2; R2 = 0.87. The leaf area with rust (Y(la)) was also well related with incidence of leaves with rust as Y(la) = 0.001 - 0.01076X +0.008376X2; R2 = 0.92. For two independent data sets from a second location obtained over two seasons, the above models satisfactorily fit the relationships for the average sporulating pustules per leaf (R2 = 0.97 and 0.96) and for the estimated leaf area with rust (R2 = 0.95 and 0.98). Therefore, the readily determined incidence can be used to estimate both measures of disease severity of coffee rust.
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Database assignments for author(s): Luiz A. Maffia

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Hemileia vastatrix	Coffee (Coffea)	Brazil (south)