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Go to Table of Contents CONTAINMENT AND ERADICATION OF PHYTOPHTHORA CINNAMOMI IN NATURAL ECOSYSTEMS C. Dunne A , R. Hartley A , W. Dunstan B , C. Crane A and B. Shearer A A Dept. Environment and Conservation, Perth. Email: Chris.Dunne@dec.wa.gov.au B Murdoch University, Perth ABSTRACT. Phytophthora cinnamomi is an introduced soil-borne plant pathogen and one of the greatest threats to the biodiversity of south-west Western Australia (WA). It spreads between plants by root-to-root contact, in surface and subsurface water flow and by movement of soil and plant material, primarily on vehicles, footwear and animals. Approximately 40% of WA’s flora are susceptible to the disease caused by P. cinnamomi. Once it has been introduced to an area, it persists, resulting in a permanent decline in ecosystem function. Infestations in native plant communities lead to canopy cover loss, hydrology changes, and increased soil temperature and moisture. The disease also alters the composition, diversity, structure and biomass within these communities. A research-based program is underway to protect vulnerable priority areas from the threat of P. cinnamomi. The program aims to identify new infestations and either contain or eradicate them before the pathogen spreads across the landscape into high biodiversity value areas. The program has successfully eradicated one infestation and contained another two within Cape Arid and Fitzgerald River National Parks. This integrated management approach involves: strict hygiene and access protocols; systematic mapping of pathogen occurrence; installation of hydrological engineering controls; vegetation destruction; herbicide, fungicide and fumigant treatments; and detailed monitoring. These techniques have broad application in other P. cinnamomi management projects or the control of other soil borne plant pathogens. INTRODUCTION The introduced soil-borne plant pathogen Phytophthora cinnamomi poses a real threat to biodiversity across Australia. To date, mitigation efforts have concentrated on reducing the rate of spread from infested areas or introduction of the pathogen into new areas. Since 2006, the Department of Environment and Conservation has been using applied research to develop techniques for managing the pathogen once introduced into natural areas. Previous work showed that fumigants such as metham sodium have been shown to eradicate the pathogen from infested areas (Dunstan et al. 2010). MATERIALS AND METHODS Site selection and analysis A number of infestations, considered being less than 12 months post-introduction, were assessed for suitability. Two sites with differing soil and landscape characteristics were selected, as well as one site already under close management (Dunne et al. 2012). Intensive sampling was conducted around their sites to define disease boundaries. Hydrological analysis was conducted to predict pathogen movement and inform engineering solutions. Soil analysis informed actions for chemical application and physical works. Weather stations were installed and high definition digital elevation modelling was conducted to provide accurate localised data. Containment Fencing was installed around the two infestations with signs of significant faunal movement. The chemical phosphite has for many years been used to inhibit the pathogen and stimulate plants’ defence systems to prolong survival. It was used at each site with a significant buffer outside the experimental areas. Impermeable plastic bunds were used to reduce the volume of water entering the site and to stop infested water leaving the containment areas. Semi-permeable membranes were tested in laboratory conditions and shown to stop pathogen movement under neutral pressure conditions. These membranes were installed on site to filter the pathogen from surface and subsurface water flow. Eradication Herbicide was applied to the infested areas to remove the host plants. In the one site with deep sand, a soil fumigant, metham sodium, was applied at depth (500 – 600 mm) and to the top soil. RESULTS Containment Fencing has been found to reduce animal movement though was not successful in complete removal of this vector. The impermeable bunds were effective in reducing the level of soil moisture within, as well as controlling water flow away from, the containment areas, even after significant rainfall events. To date, the semipermeable membranes appear to have been effective in filtering P. cinnamomi inoculum, with intensive sampling outside the infestations not isolating the pathogen despite favourable conditions. Eradication Effective herbicide application was challenging due to the desire to minimise non-target impacts. The herbicide did not result in the complete removal of living vegetation. However, this was achieved through soil fumigant application. Targeted and thorough sampling shows that the pathogen has not been able to persist. Figure 1. Application of metham sodium to eradicate a P. cinnamomi spot infestation in Cape Arid National Park. DISCUSSION This research demonstrates that the pathogen P. cinnamomi can be eradicated from natural systems post-introduction with favourable site conditions. This has great implications for the management of the plant disease and the protection of high conservation value areas. REFERENCES 1. Dunstan, W. A., Rudman, T., Shearer, B. L., Moore, N. A., Paap, T., Calver, M. C., Dell, B. and Hardy, G. (2010). Biological Invasions 12: 913-925. 2. Dunne, C. P., Crane, C. E., Lee, M., Massenbauer, T., Barrett, S., Comer, S., Freebury, G. J., Utber, D. J., Grant, M. J., Shearer, B. L. (2011). New Zealand Journal of Forestry Science 41S: S121–S132. 7th <strong>Australasian</strong> Soilborne Diseases Symposium 19
Go to Table of Contents CROP SELECTION AND TRICHODERMA TR905 INOCULATION SUPPRESSES PYTHIUM IRREGULARE ROOT DISEASE INCIDENCE AND SHIFT THE GENETIC STRUCTURE OF PATHOGEN POPULATIONS P.R. Harvey AB , B.E. Stummer A , R.A. Warren A and H. Yang B A CSIRO Ecosystem Sciences and Sustainable Agriculture Research Flagship, Waite Campus, PMB2, Glen Osmond, 5064, SA B Biology Research Institute, Shandong Academy of Sciences, Jinan, Shandong, P.R. China. Email: Paul.Harvey@csiro.au ABSTRACT. Crop selection, metalaxyl-M seed treatment and Trichoderma Tr905 inoculation were used to assess disease suppression of Pythium irregulare. Treatment efficacies were determined by quantifying soil-borne pathogen inoculum levels and root isolation frequencies. Peas were defined as the most susceptible crop, followed by canola, wheat and barley. Tr905 significantly reduced P. irregulare wheat root infection and was comparable to metalaxyl-M seed treatment. Population genetic analyses resolved significant inter- geographical and host-based differentiation within P. irregulare, indicating hostbased selection of pathogen genotypes. Crop selection, chemical and inoculant treatments shift the population dynamics, genetic structure and disease incidence of P. irregulare, providing opportunities for more effective, integrated disease management. INTRODUCTION Pythium irregulare is common in agricultural soils, reported to cause pre-emergent blight & root rot of crops & pastures (1). P. irregulare infects a broad range of hosts & inoculum carryover is hypothesised to increase disease incidence & reduce grain yields (1). Rotations are therefore, thought to be ineffective in suppressing disease. Host species have however, been reported to effect the genetic structure of P. irregulare populations (1). Determining impacts of host-mediated selection on the dynamics of P. irregulare genotypes and the relationships to disease incidence may avoid planting highly susceptible crops. Integrating crop selection, chemical and inoculants treatments will assist development of novel disease suppression strategies for P. irregulare. MATERIALS AND METHODS Crop selection (barley, canola, peas & wheat) & Pythiumselective chemical (metalaxyl-M 0.35 g ai Kg -1 seed) trials were established at Clare & Paskeville (SA). A wheat disease suppressive inoculant (Trichoderma Tr905) trial was established at Paskeville. Soil samples were collected at sowing (T0) & 12 weeks post-emergence (T1). Root samples were taken at T1. Inoculum & root isolation frequencies were quantified as described previously (1). DNA from 20 P. irregulare isolates per crop was purified and host-based populations were subjected to population genetic analyses with RFLP (1) & AFLP markers (2). Table 2. P. irregulare soil-borne inoculum & root infection frequencies resulting from Trichoderma Tr905 inoculation & metalaxyl-M (LSD inoculum = 44, LSD roots = 0.167). Treatment Inoculum 3 (g -1 soil) Isolation frequency Sowing 12 weeks 12 weeks Paskeville Untreated 240 bc 290 a 0.380 a Metalaxyl-M 230 c 280 ab 0.168 b Trichoderma 240 bc 270 abc 0.191 b Genetic structure of P. irregulare populations. Significant (P
Page 2 and 3: The following organisations sponsor
Page 4 and 5: Welcome to the Seventh Australasian
Page 6 and 7: 7 th Australasian Soilborne Disease
Page 8 and 9: THURSDAY 20 SEPTEMBER 08:30 Chair -
Page 10 and 11: TABLE OF CONTENTS KEYNOTE SPEAKERS
Page 12 and 13: ANTI-FUNGAL METABOLITES PRODUCED BY
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Page 64 and 65: Go to Table of Contents APPLICATION
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