Studies on bean yellow mosaic virus in pasture species and lupins.

Trial 90PE11 Location: South Perth. A survey was conducted to determine the extent of Bean Yellow Mosaic Virus (BYMV) infection in subterranean clover pastures. The pastures were sampled in October by officers from each of the country districts and from south Perth. 100 samples were collected from each pasture, 1 sample every 5 paces , and sent to south Perth. The ELISA test and the Gibbs and Gower formula were used to determine a percentage BYMV infection for each infected pasture. Barley yellow dwarf virus in wheat Location: Badgingarra, Wongan Hills, Goomalling-Dowerin, Northam, Katanning, Jerramungup. In 1990, very large populations of cereal aphids were found in August/September on wheat and barley crops throughout the wheat belt (including low rainfall areas), the one exception being the Geraldton region where high aphid populations were not reported. These high aphid populations were mostly the consequence of an exceptionally large aphid dispersion flight in autumn, which established many colonies in crops, and of good conditions for aphid buildup within crops during the growing season. The large autumn flight itself was the result of exceptionally high summer rains which permitted profuse growth of grasses over summer/early autumn, on which the cereal aphids built up before flying to cereal crops. Three aphid species were involved, the cereal aphid (Rhopalosiphum padi), the corn leaf aphid (R.maidis) and the rice root aphid (R.rufiabdominalis) with R.padi being the predominant species. Grasses on which cereal aphids oversummer are also the reservoir via which BYDV persists between growing seasons. Thus, the reservoir of BYDV was also exceptionally large. This coupled with the abundance of cereal aphids resulted in an unprecedented BYDV epidemic with BYDV symptoms being found widespread even in cereal crops in parts of the central and northern wheat belt in which the virus has never been reported before. BYDV serotypes PAV, RPV were detected in cereal crops and grasses. The MAV serotype was detected in grasse