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Puccinia psidii has long been considered a significant threat to Australian plant industries and ecosystems. In April 2010, P. psidii was detected for the first time in Australia on the central coast of New South Wales (NSW). The fungus spread rapidly along the east coast and in December 2010 was found in Queensland (Qld) followed by Victoria a year later. Puccinia psidii was initially restricted to the southeastern part of Qld but spread as far north as Mossman. In Qld, 48 species of Myrtaceae are considered highly or extremely susceptible to the disease. The impact of P. psidii on individual trees and shrubs has ranged from minor leaf spots, foliage, stem and branch dieback to reduced fecundity. Tree death, as a result of repeated infection, has been recorded for Rhodomyrtus psidioides. Rust infection has also been recorded on flower buds, flowers and fruits of 28 host species. Morphological and molecular characteristics were used to confirm the identification of P. psidii from a range of Myrtaceae in Qld and compared with isolates from NSW and overseas. A reconstructed phylogeny based on the LSU and SSU regions of rDNA did not resolve the familial placement of P. psidii, but indicated that it does not belong to the Pucciniaceae. Uredo rangelii was found to be con-specific with all isolates of P. psidii in morphology, ITS and LSU sequence data, and host range. [ABSTRACT FROM AUTHOR]

Calonectria ilicicola, Gliocladiopsis sp. and Ilyonectria liriodendri were isolated from diseased roots of young avocado trees. Pathogenicity studies with seedlings of three avocado cultivars, Velvick, Hass and Reed, demonstrated that Calonectria ilicicola is a severe root rot pathogen, reducing the biomass of healthy roots, and reducing plant height over time. Calonectria ilicicola was re-isolated from diseased roots. Ilyonectria liriodendri and Gliocladiopsis sp. were not pathogenic and plant height was increased after Gliocladiopsis sp. amendment compared to all other treatments in trials with cvs Velvick and Hass. [ABSTRACT FROM AUTHOR]

The isolation frequency of Microsphaeropsis sp. in spring in association with necrotic lesions on leaves in Tasmanian pyrethrum ( Tanacetum cinerariifolium) fields has increased substantially since first identification in 2001. Examination of morphological features and sequencing of the internal transcribed spacer region (ITS) resulted in the identification of a new species, herein described as Microsphaeropsis tanaceti sp. nov. The pathogenicity of three M. tanaceti isolates to two pyrethrum cultivars was confirmed by inoculating glasshouse-grown plants in three experiments. No significant differences in the susceptibility of the two cultivars to infection by M. tanaceti were found. Symptoms were tan-coloured spots which coalesced around the margins of the leaves. Therefore, the name ‘tan spot’ is proposed for this new disease of pyrethrum. The sensitivity of seven M. tanaceti isolates to difenoconazole and azoxystrobin, commonly used fungicides for the management of foliar diseases in spring, was assessed under in vitro conditions. Sensitivity testing for difenoconazole was conducted using a mycelial growth assay on potato dextrose agar, whilst testing for sensitivity to azoxystrobin used a conidial germination assay on water agar. Microsphaeropsis tanaceti was found to be more sensitive to azoxystrobin than difenoconazole, with complete inhibition of conidial germination at concentrations above 0·625 µg a.i. mL−1. By comparison, concentrations of 50 µg a.i. difenoconazole mL−1 or greater were required for significant inhibition of mycelial growth. It therefore appears likely that there is currently some control of tan spot as a result of the use of azoxystrobin and to a lesser extent, difenoconazole, for the control of other diseases. [ABSTRACT FROM AUTHOR]

Australian wheat consigned for export from Australian ports was surveyed in March 2004 using a national diagnostic protocol for detection and identification ofTilletia indica. No ustilospores ofT. indicawere detected, confirming previous surveys which have failed to detectT. indicain Australia. However, the survey detected moderate levels of the common smutsTilletia caries(syn.Tilletia tritici),Tilletia laevisandUrocystis agropyri, and very low levels (average fewer than six ustilospores per 150 g sample) of an unidentified dark, tuberculate-sporedTilletiain≈ 60% of samples tested. Comparison with herbarium specimens enabled identification of the majority of the tuberculate ustilospores asTilletia ehrhartae, a smut fungus known to infect onlyEhrharta calycina(perennial veldt grass) and which is common in southern Australia. A smaller number of tuberculate smut ustilospores were identified asTilletia walkeri, a smut ofLoliumspp. recorded in Australia but apparently uncommon. BothT. ehrhartaeandT. walkeribear sufficient resemblance toT. indicafor misidentifications to be possible where only a very few ustilospores are seen, althoughT. ehrhartaeustilospores are always<25  µm in diameter. The frequent presence of ustilospores of bothT. ehrhartaeandT. walkerias contaminants of Australian wheat grain exports has significance for diagnosticians testing Australian export wheat, as it demonstrates the potential for tuberculate ustilospores of species other than those covered in existing diagnostic protocols to be misidentified asT. indica. This paper describesT. ehrhartaein detail, and provides criteria for its differentiation fromT. indica,T. walkeriand some other species. [ABSTRACT FROM AUTHOR]

The effect of temperature, dew period, inoculum concentration and host maturity on the growth and development of Emex australis after inoculation with Phoinopsis emicis was studied in controlled environments. Disease was assessed by recording changes in the length of stems, number of fully expanded leaves, dry weights, number of fruits and disease severity index. Disease was as severe at 18°C as it was at 28°C. There was a trend of increased disease with longer dew period. Inoculum concentrations of 1 &time; 106 and 1 &time; 107 conidia per ml resulted in a significant net reduction in stem growth compared with lower concentrations. Progressively higher disease ratings occurred as the inoculum concentration increased to 1 &time; 107 conidia per ml. There were no significant effects of inoculation with P. emicis on either seedlings, rosettes or flowering rosettes, but 10-week-old plants were highly susceptible to infection and stem collapse. The implications of these results for the potential development of P. emicis as a mycoherbicide are discussed. [ABSTRACT FROM AUTHOR]