Link to home

Characterization of the Spatiotemporal Attributes of Sclerotinia Flower Blight Epidemics in a Perennial Pyrethrum Pathosystem

November 2010 , Volume 94 , Number  11
Pages  1,305 - 1,313

Sarah J. Pethybridge, Botanical Resources Australia–Agricultural Services Pty. Ltd., Ulverstone, Tasmania, 7315, Australia; Frank S. Hay, Tasmanian Institute of Agricultural Research (TIAR), University of Tasmania–Cradle Coast Campus, Burnie, Tasmania, 7320, Australia; and David H. Gent, United States Department of Agriculture–Agricultural Research Service, Forage Seed and Cereal Research Unit, Oregon State University, Department of Botany and Plant Pathology, Corvallis 97331



Go to article:
Accepted for publication 22 June 2010.
ABSTRACT

Sclerotinia flower blight, caused by Sclerotinia sclerotiorum, causes substantial losses in Australian pyrethrum fields. The spatiotemporal characteristics of epidemics were characterized in five fields over 3 years. Log likelihood tests indicated that the β-binomial distribution fit better than the binomial distribution for 92% of the data sets. The index of dispersion, D, was significantly greater than 1 in 97% of the data sets. The estimated parameters of the slope and intercept terms of the binary power law were 1.631 (standard error [SE] = 0.059) and 0.678 (SE = 0.099), indicating a high degree of aggregation at the individual sampling unit scale. In 69% of the data sets, the magnitude of the first-order autocorrelation coefficient , was significantly greater than 0. In 11 of the 12 epidemics, the monomolecular model provided the best fit, indicative of monocyclic processes. A significant spatial association between apothecia and incidence of Sclerotinia flower blight within the lag of one sampling unit was also quantified. This study suggests that S. sclerotiorum apothecia emergence was closely synchronized with flower development, and epidemics were dominated by localized sources of ascosporic inoculums. This research provides the basis for improved management strategies for Sclerotinia flower blight in pyrethrum.



© 2010 The American Phytopathological Society