Pasture ecology of barley yellow dwarf viruses at Sandford, Tasmania

Samples of cocksfoot ( Dactylis glomerata ), fescue ( Festuca arundinacea ), phalaris ( Phalaris aquatica ) and ryegrass ( Lolium perenne ) were collected every 4-6 weeks for 2.5 years from two sets of replicated plots, one on a heavy soil and the other on a light soil 200 m away. Rhopalosiphum padi was the predominant aphid species; it was more frequent at the heavy soil site. Sitobion fragariae and Metopolophium dirhodum occurred infrequently during the last 12 months of the survey.
Only PAV (57%), RPV (26%) and mixed infections (17%) of these barley yellow dwarf viruses were detected in the 4100 tillers sampled. Virus incidence increased over the sampling period and was consistently higher at the heavy soil site. RPV only became frequent during the last 12 months.
Virus incidence was higher in fescue (21%) and ryegrass (27%), in which PAV predominated, than in cocksfoot (6%) and phalaris (7%), in which RPV finally predominated.