Wheat crop surveys in southern NSW. 3. The incidence of take-all

Abstract

Heavy take-all (Ophiobolus graminis Sacc.) infection was observed in 24 per cent of the 463 wheat crops surveyed in southern New South Wales in 1963. Simple tests of independence showed that the occurrence of heavy take-all infection was positively associated with weed density and cropping intensity. Clover ley history, nature of the previous crop, length of fallow period, sowing time, and weed type did not appear to be significantly associated with the occurrence of take-all. When the possibility of interactions was considered, heavy take-all was found most commonly in the early sown, heavily weed infested second crops after wheat or barley. Sixty per cent of these crops were heavily infected. The results of this survey suggest that a number of hypotheses developed under controlled experimental conditions do not hold widely in the field