Downy mildew, caused by Peronospora arborescens, has become the major disease affecting oilseed poppy (Papaver somniferum) since its first record in Tasmania in 1996. Two field trials conducted in 2000 and 2001 studied the progression and spatial distribution of downy mildew epiphytotics. The logistic and exponential models best described the progression of disease incidence and severity, respectively. Incidence and severity increased rapidly following canopy closure. In 2001, incidence increased from 0.16%, prior to canopy closure, to 100% at late flowering (40 days). Spatial analyses of epiphytotics were conducted by fitting the beta-binomial and binomial distributions, median runs analysis, and the spatial analysis by distance indices. All analyses demonstrated that the distribution of incidence and severity was strongly spatially aggregated from canopy closure until at least late flowering. These results suggest that secondary spread from a few primary infections is the major factor in epiphytotics.

Item Type:	Refereed Article
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Crop and pasture production
Research Field:	Crop and pasture protection (incl. pests, diseases and weeds)
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Other plant production and plant primary products
Objective Field:	Other plant production and plant primary products not elsewhere classified
UTAS Author:	Scott, JB (Dr Jason Scott)
UTAS Author:	Hay, FS (Dr Frank Hay)
UTAS Author:	Wilson, CR (Professor Calum Wilson)
ID Code:	23920
Year Published:	2003
Web of Science® Times Cited:	21
Deposited By:	Agricultural Science
Deposited On:	2003-08-01
Last Modified:	2004-04-21
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