Application of the logistic-normal-binomial distribution to the analysis of Eutypa dieback disease incidence

The analysis of disease incidence data when diseased plants are aggregated in clusters is discussed. The logistic-normal-binomial distribution provides a basis both for analysing experiments according to their factor structure and for describing the observed frequency distribution of affected plants per sampling unit. These analyses are illustrated with data from disease assessments of Eutypa dieback of grapevine in Californian vineyards. A comparison of the results of this study with those of a previous one suggests that clustering of Eutypa dieback may occur on different scales, dependent on the presence of perithecia of the causal organism, Eutypa lata, in a vineyard.