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 aggreg ated in clusters is discussed. The logistic-normal-binomial distributi on provides a basis both for analysing experiments according to their factor structure and for describing the observed frequency distributio n 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.