Effect of crop age on primary gradients of late leaf spot (Cercosporidium personatum) on groundnut     

S. SAVARY  G. VAN  SANTEN 《Plant pathology》1992,41(3):265-273

Artificial sources of late leaf spot were established by inoculation of one plant at the centre of several groundnut plots differing in age. First-generation dispersal and resulting primary gradients of disease were then compared. The gradients were corrected for source strength, spontaneous infection (primary gradient), and interplot interference (first-generation dispersal). The shapes of the gradients for spore dispersal and of the gradients of disease corresponded for each age of groundnut plot, but differed between the ages. The slopes of gradients were steeper in the older plots. Spore dispersal and the resulting disease gradients were not isodiametric, gradients being most protracted in a north-to-north westerly direction. The results suggest that the strength of the sources was reduced by abscission of infected leaves in the sources of the younger plots, whereas accessibility of the canopy to the transported spores was reduced by increasing canopy density in the older ones.  相似文献   

A dynamic model simulating infection of apple leaves by Venturia inaequalis   总被引：2，自引：0，他引：2  

X.-M. XU  D. J. BUTT  G. VAN  SANTEN 《Plant pathology》1995,44(5):865-876

A new dynamic model of the infection of apple leaves by Venturia inaequalis is described. The model begins with the release of spores by rain and incorporates the effect of light on the discharge of ascospores from pseudothecia. The model then simulates infection through the sub-processes of germination, appressorium formation and penetration, separately for ascospores and conidia landed concurrently on wet leaves. The rate of the infection process is determined using different equations for ascospores and conidia. Spore mortality when leaves dry is determined by the stage of infection and RH in the dry period. The infection process is driven by surface wetness, temperature and RH. The progress of each infection period is measured as infection efficiency (IE), namely the percentage of landed spores which have penetrated and thereby infected leaves. The final IE quantifies the favourability of weather in each infection period. In orchard tests in each of three years, the new model detected crucial infection periods in spring and early summer which accounted for outbreaks of leaf scab. These periods were not detected by a static model based on Mills'criteria. The models performed similarly in detecting infection periods later in summer.  相似文献