Epidemiology of Cercospora Leaf Spot on Sugar Beet: Modeling Disease Dynamics Within and Between Individual Plants

Abstract

Disease dynamics of Cercospora leaf spot (CLS) of sugar beet was analyzed at two hierarchical scales: as vertical profiles within individual plants and in relation to disease on neighboring plants. The relative contribution of different leaf layers to increase in CLS was analyzed using a simple continuous-time model. The model was fitted to data from two field trials in the Netherlands: one in an area with a long history of CLS, the other in an area where CLS has only recently established; in each case these were unsprayed and twice-sprayed treatments. There were differences in the relative contribution of different leaf layers to disease increase on the target leaf layer according to the CLS history and whether the plants were sprayed or unsprayed. In both field trials, parameter estimates giving the relative contribution of the target leaf layer to disease increase at that leaf layer were higher than those for the lower leaf layer. On only a few occasions the contribution of an upper leaf layer to disease increase at the target leaf layer was significant. Thus, CLS increase at the target leaf layer was determined mainly by disease severity at that leaf layer and to a lesser extent by disease at the lower leaf layer. Our continuous-time model was also used to analyze CLS increase on an individual sugar beet plant in relation to its own and its neighbor's level of disease in field trials at five locations in the two CLS areas over two years. In all field trials, the contribution of the target plant itself to disease increase (auto-infection) was larger than that of its neighboring plants (allo-infection). The overall analysis in the two CLS areas also indicated a larger contribution of the target plant to its disease increase than of neighboring plants, and this pattern was also apparent in a pooled analysis across all sites. Thus, CLS increase on a sugar beet plant was mainly determined by the disease severity on that plant and to a lesser extent by its within-row neighboring plants.

Temporal and Spatial Development of Cercospora Leaf Spot of Faba Bean Influenced by In Situ Inoculum

“…An alternative explanation, that a limited amount of inoculum may have been present in the negative soil zone, is unlikely because the time of disease onset would have been similar in both soil zones (Madden et al 2007;Vereijssen et al 2006). The fact that the incidence of Cercospora leaf spot increased rapidly in the negative soil zone after 77 DAS reflects secondary infections (Vereijssen et al 2007).…”

Challenges and Prospects for Building Resilient Disease Management Strategies and Tactics for the New York Table Beet Industry

“…Conidia produced within the lesions enable multiple infection cycles to occur within one growing season and result in polycyclic disease epidemics [38]. The dispersal of conidia by rain splash and wind-blown rain infers short dispersal distances from 'local' inoculum within the field of interest [46][47][48]. Spread resulting from diseased, alternative hosts or infested crop residues within a field may also be a likely explanation for initiation of CLS epidemics as randomly distributed foci.…”

A General Model for the Effect of Crop Management on Plant Disease Epidemics at Different Scales of Complexity

“…In this work, we operated the model using plausible parameter values for Cercoscopa beticola, causing Cercospora Leaf Spot (CLS) on sugar beet, as an example. Parametrization was based on the literature [25][26][27][28][29][30]. The initial disease level was set at 0.3% of affected leaf area (i.e., y 0 = 0.003).…”