Exploring Spatiotemporal Patterns of Phoma Black Stem in Sunflower

摘要

Field experiments were conducted over two growing seasons with three sunflower cultivars to explore the spatiotemporal dynamics of phoma black stem epidemics and to test hypotheses pertaining to (i) disease spread from a known inoculum source; (ii) spatial patterns of the disease; (iii) disease spatiotemporal association; and (iv) association between disease intensity and sunflower defoliation. The spatial patterns of disease were random in most of epidemics, and disease gradients were not detected. Our results suggest absence of secondary infections, that is, that the studied phoma black stem epidemics were monocyclic under the experimental conditions reported here. Significant associations between the number of dead leaves per plant and the number of phoma black stem lesions per plant were detected towards the end of epidemics.