A survey of barley yellow dwarf virus in Australia 1963

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Abstract
A survey of barley yellow dwarf virus (BYDV) in cereal crops in Queensland, New South Wales, Victoria, and Tasmania was carried out between 18 September and 4 October 1963. BYDV was identified by symptolllli in the field and confirmed in New Zealand by transmission tests with Rhopalosiphum padi (L.) fed on the leaf and stem samples of cereals and grasses collected during the survey. It was correctly identified in all samples except oats affected by drought in Queensland and by excessive soil moisture in Tasmania. BYDV caused an average loss of about 2 per cent over the 52 cereal crops examined, but only 10 per cent of crops had losses above 10 per cent. The low incidence of BYDV in many crops in Queensland, even where there were large numbers of cereal aphids (R. padi) was probably due to the relative absence of perennial pasture as a source of BYDV, and also because of the high field populations of coccinellid adults and larvae (Verania frenata Erichson). The low incidence of BYDV in Tasmania was associated with a low level of cereal aphid (R. padi) in cereal crops, as a possible consequence of small autumn flights and a cold wet winter. R. padi was undoubtedly the main vector of BYDV in Australia because it was the most abundant species and successfully transmitted the majority of samples tested in New Zealand. It occurred mainly at and below ground level on the stem bases and leaf sheaths of between 20 per cent and 100 per cent of cereal plants at the tillering stage, seen in Victoria, New South Wales, and Queensland on this survey. Rhopalosiphum maidis (Fitch.) was found in large numbers only once on a barley crop—at late jointing stage at Narrabri. Macrosiphum avenae, miscanthi (Takahashi) was abundant on seed heads of wheat and oats at two localities at Sydney and at Thulimbah (Queensland).

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