A Quantal Method for Determining Numbers of Erwinia carotovora var. carotovora and E. carotovora var. atroseptica in Soils and Plant Material

SUMMARY: A quantal method is described, based on the maximum likelihood method, which was found especially suitable for quantitatively estimating small populations of Erwinia carotovora in soils and plant material. Drops from serial dilutions of the test material are placed on replicated defined areas of a solid, semiselective medium with a pectate overlayer. The presence or absence of one or more of the characteristic, deep cavities formed by E. carotovora colonies in the pectate layer is the basis of the quantal count from which estimates of the population size can be derived.