Epidemiological studies on cercospora leaf spot of sugar beet

Abstract

In the glasshouse, inoculation of sugar beet with Cercospora beticola followed by 16 h of high humidity produced visible disease only with at least four conidia per cm2 of leaf area. Disease became more severe after increasing periods of high humidity in the range of 0–24 h. In the field, spraying plants with water enhanced disease spread from a focus. Disease progress curves were sigmoid. Apparent infection rate declined towards the end of the season, possibly because of high temperature. In approximate agreement with prediction, epidemic development was delayed when initial inoculum was reduced. Reduced infection, resulting from either reduced initial inoculum or delayed inoculation, decreased the adverse effect of disease on sugar yield.

Distribution and Epidemic Pattern of Cercospora Leaf Spot Disease of Sugar Beet in Egypt.

“…Disease progress curves were sigmoid and the infection rate tends to declined towards the end of the season, possibly due to an unfavorable environmental conditions. (Pundhir & Mukhopadhyay, 1987).…”

Estimation of a Time-varying Apparent Infection Rate from Plant Disease Progress Curves: A Particle Filter Approach

“…It is well known that the dynamics of field epidemics are disturbed by within-season continuous variations in weather at short (hourly) time scales which affect processes of the disease cycle, mainly the apparent infection rate. For instance, a decline in obtained from three assessments in time in Cercospora leaf spot (t) r ( Cercospora beticola ) epidemics in sugar beet was associated with variations of temperature that turned less favorable for new infections later in the season (Pundhir and Mukhopadhyay, 1987). Waggoner (1986) assembled mathematical equations to account for parabolic and sinusoidal patterns around an optimum (t) r in order to reflect the effect of climatic variations on late blight epidemics.…”

Development of a field biotest using artificial inoculation to evaluate resistance and yield effects in sugar beet cultivars against Cercospora beticola

“…Pfleiderer and Schäufele (2000) proposed that the inoculum density obtained using the method of Adams et al (1995) should be reduced for a widespread testing system. Pundhir and Mukhopadhyay (1987) showed that (i) in greenhouse infection experiments, a minimum inoculum concentration was required to cause visible lesions and (ii) that inoculum concentration, final disease index and sugar yield reduction were positively related.…”