Abstract This paper discusses the role of a pothecia of Pyrenopeziza brassicae Sutton & Rawlinson in the disease cycle of light leaf spot of brassicas. Apothecia survived for up to 27 weeks on the soil surface under a weed canopy but for less than 4 weeks when buried in the soil. Apothecia stored for up to 50 weeks on dry cauliflower residues in the laboratory discharged ascospores when wetted. Ascospores discharged on to glass slides remained viable for up to 8 weeks at about 20°C and 70% RH. Less than 1% of conidia incorporated into unsterilised volcanic loam remained viable after 10 days as determined by direct counts, but bioassay showed that some conidia remained viable for up to 10 weeks. Seeds from severely diseased cauliflower seedheads contained the pathogen but tests indicated that the disease was not seed-transmitted. P. brassicae was not found on any of the common cruciferous weeds present in vegetable brassica crops in the Pukekohe district. Only summer-grown plants of oilseed rape were susce...
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