Resolving confusions about jarrah dieback - don’t forget the plants

The name jarrah dieback has been used for two different disorders, leading to considerable confusion. It was coined in the 1940s to describe the sudden death of groups of jarrah (Eucalyptus marginata) trees in south western Western Australia, which occurred on poorly drained sites, following exceptionally heavy rainfall. In the 1960s these sites were shown to be infested by Phytophthora cinnamomi and jarrah deaths were attributed to it, even though it was only isolated from 5 % of sampled trees. Also the definition of jarrah dieback was expanded to include deaths of many other plants on infested sites, from which P. cinnamomi was more readily isolated. Jarrah trees die from severe water deficiency, indicating problems with water conduction through roots. Xylem vessel diameters vary along roots, being narrow at the root collar, while distally they are larger, providing water storage. Jarrah transpires vigorously during summer, accessing water at depth on sites with deep soil, but being more dependent on internally stored water when root systems are shallower. Following waterlogging, sapwood vessels become blocked with tyloses, reducing both conductivity and potential water storage; such trees may have insufficient water reserves for summer survival. In jarrah P. cinnamomi is unlikely to cause water deficiency because sapwood invasion is rapidly contained in healthy roots. Recent investigations into P. cinnamomi invasion and host responses in other plants show that it can potentially cause a vascular wilt in Banksia spp. and chronic, symptomless infections in herbaceous plants. Susceptibility to waterlogging damage, and/or mortality resulting from infection by P. cinnamomi can only be clarified by detailed knowledge of the hosts and their vulnerabilities. This is essential for making diagnoses, devising management strategies, and avoiding the confusions of the past

Determinants of emergency response willingness in the local public health workforce by jurisdictional and scenario patterns: a cross-sectional survey

<p>Abstract</p> <p>Background</p> <p>The all-hazards willingness to respond (WTR) of local public health personnel is critical to emergency preparedness. This study applied a threat-and efficacy-centered framework to characterize these workers' scenario and jurisdictional response willingness patterns toward a range of naturally-occurring and terrorism-related emergency scenarios.</p> <p>Methods</p> <p>Eight geographically diverse local health department (LHD) clusters (four urban and four rural) across the U.S. were recruited and administered an online survey about response willingness and related attitudes/beliefs toward four different public health emergency scenarios between April 2009 and June 2010 (66% response rate). Responses were dichotomized and analyzed using generalized linear multilevel mixed model analyses that also account for within-cluster and within-LHD correlations.</p> <p>Results</p> <p>Comparisons of rural to urban LHD workers showed statistically significant odds ratios (ORs) for WTR context across scenarios ranging from 1.5 to 2.4. When employees over 40 years old were compared to their younger counterparts, the ORs of WTR ranged from 1.27 to 1.58, and when females were compared to males, the ORs of WTR ranged from 0.57 to 0.61. Across the eight clusters, the percentage of workers indicating they would be unwilling to respond regardless of severity ranged from 14-28% for a weather event; 9-27% for pandemic influenza; 30-56% for a radiological 'dirty' bomb event; and 22-48% for an inhalational anthrax bioterrorism event. Efficacy was consistently identified as an important independent predictor of WTR.</p> <p>Conclusions</p> <p>Response willingness deficits in the local public health workforce pose a threat to all-hazards response capacity and health security. Local public health agencies and their stakeholders may incorporate key findings, including identified scenario-based willingness gaps and the importance of efficacy, as targets of preparedness curriculum development efforts and policies for enhancing response willingness. Reasons for an increased willingness in rural cohorts compared to urban cohorts should be further investigated in order to understand and develop methods for improving their overall response.</p

Relative importance of site, weather and Phytophthora cinnamomi in the decline and death of Eucalyptus marginata – jarrah dieback investigations in the 1970s to 1990s

Jarrah dieback was the name given to the sudden death of Eucalyptus marginata in the southwest ofWestern Australia, a serious economic problem. Although deaths were attributed to Phytophthora cinnamomi in the 1960s, the supporting evidence was weak; these deficiencies were not realised until 1980. Renewed interest in jarrah pathology showed that the incidence and severity of root lesions caused by P. cinnamomi in live trees was low, but in recent deaths it could be isolated from the root collar and large roots of some, but not all trees. Jarrah deaths result from hydraulic failure, implying extensive sapwood damage. This is unlikely to result from P. cinnamomi infection, which preferentially invades phloem, but could result from waterlogging, which causes tyloses to form in xylem vessels so they no longer conduct water. Tylosed root sapwood has been reported from investigations into jarrah deaths. An interpretation of past deaths based on stress factors better fits where and when deaths occur. This is within 3 years of exceptionally heavy rainfall, an inciting factor. Predisposing conditions are sites with some form of poor drainage, such as water-gaining sites, or those with impeded sub-soil drainage. Recent logging further increases site wetness. Phytophthora cinnamomi should be seen as a contributing factor, which is normally compartmentalised by the host, but can spread extensively in dying trees