Studies on the epidemiology of peach rosette and decline disease in Victoria

Abstract

The spread of peach rosette and decline dlsease (PRD) was studied in two clingstone peach orchards, located 24 km apart in the Goulburn Valley of Victoria. Over 11 years the incidence of diseased trees in an orchard of cv. Golden Queen increased from 0.9 to 91.5%, while in an orchard of cv. Pullar's Cling the proportion of diseased trees rose from 1.5 to 29.6% over 5 years. The apparent infection rates were identical in both orchards over the first 5 years of the two epidemics.

In both orchards, a significantly higher proportion of healthy trees growing adjacent to previously diseased trees became infected in subsequent seasons. This pattern of spread of the disease is discussed in relation to pollen transmission of the viruses and the foraging habits of bees.

The spread of PRD was reduced by 29.4% over 2 years by the grubbing of all visibly diseased trees before flowering in a planting of cv. Golden Queen. Removing the flowers from diseased trees at the 'pink bud' stage also reduced the rate of spread of the disease by 13.8% in 1 year. Removing newly diseased limbs at the crotch of the tree within 4 weeks of flowering, however, did not prevent the spread of the disease into the rest of the tree.