Variation in severity of target spot, caused by Aulographina eucalypti, in a eucalypt species and provenance trial in Victoria

Angus J. Carnegie and Philip J. Keane

Abstract

Target spot caused by the fungus Aulographina eucalypti was assessed from spring 1990 to summer 1991 on 44 provenances of 14 Eucalyptus species to determine the variation in susceptibility to the pathogen. A disease assessment scale for target spot was developed specifically for this study based on the development of lesions caused by A. eucalypti and the proportion of leaf area affected. Significant variation was observed among the 44 provenances in both spring and summer, with provenances from E. globulus (all provenances except Eden), E. nitens, E. cypellocarpa, E. oreades, E. sieberi and E. viminalis scoring the highest for target spot. Provenances from E. quadrangulata, E. saligna, E. botryoides and E. elata all scored low for target spot, as did E. globulus provenance Eden. Variation within species for E. botryoides, E. globulus, E. nitens, E. saligna and E. viminalis was also significant. In general, variation between provenances within species was much less than variation between species. Severity of target spot on E. globulus (also assessed in winter 1990) increased from winter to spring and again from spring to summer. The pathogen was recorded on all 14 species in the trial, including two new host records. This paper also reports new host records from field collections by the first author over the past 12 years, and from examination of herbarium specimens, adding 35 new host records for A. eucalypti and five new host records for Australia.

Keywords: Eucalyptus, leaf pathogen, disease assessment scale, new host records.

Australasian Plant Pathology 32(3) 393 - 402 (2003) doi:10.1071/AP03043