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SUMMARYThe pupae of Erioischia brassicae (Bouché) overwinter in diapause, which extends for 105–126 days at a constant temperature of 41° F. (5° C.) and terminates, in the field, between the end of January and the beginning of February. Morphogenesis is completed at constant temperature after an accumulation of about 368 day degrees above 42° F., and in the field at Wellesbourne the first flies usually emerge during April.Phenological relationships of emergence and beginning of oviposition with accumulated day degrees and the flowering of Anthriscus sylvestris appear to provide reliable methods for the prediction of the emergence of the first flies and for the determination of the appearance of the first eggs in the field.

Most of the causal agents were polyphagous species that infect many other host plants both overseas and in Australia. All powdery mildews infecting native plants in Australia were phylogenetically closely related to species known overseas. The data indicate that Australia is a continent without native powdery mildews, and most, if not all, species have been introduced since the European colonization of the continent.