Identification and characterization of disease suppressive soils in the Western Region

The main aim of this project was to identify, confirm and characterise cereal disease suppressive sites in Western Australia (WA) to rhizoctonia root rot (Rhizoctonia solani AG8), take-all (Gaeumannomyces graminis var. tritici), crown rot (Fusarium pseudograminearum) or root lesion nematodes (RLNs). Eleven sites were identified as having suppression to either rhizoctonia root rot or fusarium crown rot. Disease suppression to rhizoctonia root rot was identified to have a biological basis. Suppression to rhizoctonia root rot was observed to occur in up to three consecutive years for one site. While the management practices were not able to be identified, this project confirmed that disease suppression occurs in WA soils and environments

Yield loss from crown rot of wheat, barley and oat varieties at two sowing dates - National Crown Rot Program, Wongan Hills 2018 - Local Research and Development Results 2018/2019

No significant yield losses to applied crown rot inoculum were measured in the milling oat varieties considered, while wheat and barley varieties showed up to 24% and 11% yield losses, respectively. While sowing date affected the grain yield of some wheat and barley varieties, the oat varieties considered showed no significant response to sowing date in this experiment. The application of crown rot inoculum reduced the yield of all crop types in both sowing dates, with the magnitude of losses exacerbated with delayed planting. To minimise the level of yield loss from crown rot, determine the levels of inoculum present prior to sowing and if required, choose a wheat or barley variety that has lower yield loss to crown rot if sowing back into cereal

Integrated disease management options to control Rhizoctonia bare-patch in wheat

. Rhizoctonia bare-patch (Rhizoctonia solani AG8) is a major problem across Western Australia’s cereal growing regions. Additional disease management options are needed as the current do not offer adequate control in severe paddocks. Three field trials were conducted: 1) cultivation below the seed and Dividend® seed treatment resulted in the lowest R. solani inoculum level at anthesis compared to either treatment alone; 2) a new fungicide injected below the seed increased yield significantly when applied at the highest rate, although there were no differences in disease on roots; and 3) a test of rotation crops showed the soil inoculum levels of R. solani were elevated by barley and wheat, but canola and fallow plots resulted in an overall decline. The results support the recommendation to farmers that in paddocks with a history of Rhizoctonia bare-patch, use cultivation below the seed and a registered fungicide. Also, it is suggested that a break crop of canola or fallow may be useful preceding cereals, although the disease level in the following wheat crops is yet to be assessed. Reduced disease and yield improvements were demonstrated with the new fungicide, but work on this and other new fungicides is continuing

Postharvest blown-arc plasma treatment did not reduce Fusarium graminearum or its mycotoxins in field-infested wheat grain

The increasing prevalence of Fusarium graminearum, a major causative pathogen of Fusarium head blight in cereal crops, leads to contamination of grain with mycotoxins, which necessitates the development of effective management strategies. This study investigated whether postharvest Blown-Arc plasma treatment could reduce F. graminearum and associated mycotoxins in field-infested grain. Postharvest Blown-Arc plasma treatment for 60 or 180 s was trialled to reduce Fusarium graminearum and deoxynivalenol (DON) mycotoxins in field-infested wheat grain. Changes in fungal components of the grain microbiome following the treatment were assessed using metabarcoding analysis of the nuclear ribosomal internal transcribed spacer gene region, and liquid chromatography mass spectrophotometry was used to measure changes in concentrations of the mycotoxins deoxynivalenol (DON), DON-3-glucoside (DON3-G) and 3-acetyl-DON (3-ADON). Fusarium spp. were the most common taxa in the grain over two seasons, with the relative abundance being higher in 2020 (72%) compared to 2021 (45%). Postharvest plasma treatment of field-infested grain for 60 or 180 s did not significantly lower Fusarium abundance. Alpha and beta diversity of the natural mycobiota in the grain were also unaffected. The concentrations of mycotoxins were not significantly different after the treatments, except that in the 2021 trial, the 180 s treatment caused a significant increase in DON concentration. We concluded that the postharvest plasma treatment used in this study did not reduce Fusarium contamination or the concentration of mycotoxins, DON, DON3-G and 3-ADON in field-infested grain. The results highlight the importance of using field-infested grain in experiments, as opposed to grain inoculated under laboratory conditions, which provides only superficial infection. This approach is crucial for accurately understanding the dynamics of treatment efficacy

Fungi and oomycetes in open irrigation systems: knowledge gaps and biosecurity implications

Water used for the irrigation of plants has the potential to harbour and spread plant pathogens yet little research is conducted within this field. This review was undertaken to critically review our understanding of water-borne fungal and oomycete plant pathogens in open irrigation systems, particularly in the context of plant biosecurity. It was determined that very limited data exists on these plant pathogens, with the majority of previous studies only recording pathogen presence. There are significant gaps in our knowledge of pathogen survival and spread, and very limited information on their ability to cause disease when contaminated irrigation water is applied to crops. This review has highlighted the need for new research on the epidemiology and pathogenicity of putative plant pathogens isolated from water, in order to determine their risk to crops. The importance of regular monitoring of irrigation systems for the early detection of plant pathogens is also discussed

Targeted liquid delivery of fungicides: a new tool for Rhizoctonia root rot control - Eyre Peninsula Farming Systems Summary 2014

This three year trial program contributed to Uniform being registered in late 2014 for liquid application in-furrow and on the soil surface to control Rhizoctonia root rot. Uniform banding treatments had better efficacy than Vibrance seed treatment. Banding treatments were associated with more significant and bigger yield responses, with dual banding of Uniform in-furrow 3-4 cm below the seed and on the surface behind the press wheel giving the most consistent yield and root health responses across seasons. Efficacy data was also generated to support registration for the liquid application of coded fungicide BYF14182 in-furrow to control Rhizoctonia. Registration is pending and expected in early April. • Yield responses achieved by banding BYF14182 in furrow were not significantly different from EverGol Prime seed treatments. However, banding in-furrow combined with seed treatment significantly improved root health compared to banding in-furrow or seed treatment alone. Fungicide responses did vary from season to season suggesting there is an environmental component affecting efficacy. Yield responses were generally bigger in the better seasons. Growers now have greater flexibility in choosing a method of fungicide application for Rhizoctonia control, which can also offer improved efficacy. Importantly, fungicides still need to be used as part of an integrated management package. Banding will reduce patch incidence and severity but not eliminate patching altogether

Fishing for Phytophthora from Western Australia’s waterways: a distribution and diversity survey

During one spring season, 12 Phytophthora species, two Phytophthora hybrids, three Halophytophthora species and three Phytopythium species, were isolated from 48 waterways across Western Australia. The waterways were sampled using nylon mesh bags containing leaf baits of up to six different plant species and were isolated by plating necrotic lesions on these onto Phytophthora-selective agar media. Phytophthora species were isolated from all except one waterway. Of the Phytophthora species isolated, eight are known while the remaining four are undescribed taxa. Six of the Phytophthora species and the two hybrids are from clade 6. The two hybrids and P. inundata were the predominant species recovered. Recoveries from different plant leaf baits varied with the best two baits being Pittosporum undulatum and Banksia attentuata; and from these two combined all Phytophthora species were isolated. There was a marked difference in the Phytophthora diversity in the waterways from different regions. This is the first comprehensive study from Australia to examine the Phytophthora communities in waterways, and advances our understanding of the role of these oomycetes in natural and anthropized ecosystems

Potential susceptibility of Australian flora to a NA2 isolate of Phytophthora ramorum and pathogen sporulation potential

Phytophthora ramorum is an invasive plant pathogen and the cause of considerable and widespread damage in nurseries, gardens and natural woodland ecosystems of the USA and Europe. It is considered to be a significant plant disease as it could cause biodiversity loss and severe economic losses in plant industries in areas where it is not yet known to exist, such as Australasia. Foliar susceptibility and sporulation potential were tested using detached-leaf assays for 70 Australian native plant species sourced from established gardens and arboreta in California using a NA2 isolate of P. ramorum. Correa‘Sister Dawn’, Eucalyptus regnans, Isopogon cuneatus, I. formosus, Leptospermum scoparium, L. lanigerum and Melaleuca squamea were identified as potentially highly susceptible host species. Hedycarya angustifolia, Olearia argophylla, Phyllocladus aspleniifolius, Pittosporum undulatum and Podocarpus lawrencei were identified as potentially resistant. All 70 species were able to be infected with P. ramorum, as confirmed by reisolation. Putative sporulating hosts include five members of the Myrtaceae, Agonis flexuosa, Corymbia ficifolia, Eucalyptus haemastoma, E. delegatensis and E. viminalis. As a part of a precautionary strategy, the potentially highly susceptible species found in this study are suitable candidates for targeted surveillance programmes in high-risk incursion areas of Australia and within the global horticultural trade