Sigastus weevil - an emerging pest of macadamias in north Queensland

A large weevil was found infesting macadamia nuts on the Atherton Tableland during the 1994/95 season. It was unrepresented in various Australian insect collections but thought to belong to the genus Sigastus. This paper reports some preliminary studies on its biology, pest status and control. From 4-6 weeks after first nut-set adult females commence laying single eggs through the husk, after first scarifying an oviposition site. The nut stalk is then cleaved leading to rapid abscission. Nuts were generally attacked up until hard shell formation. Weevil larvae consumed whole kernels, with % survival higher and larval duration shorter in larger nuts. Infestation rates increased with increasing nut diameter, reaching 72.8% of fallen nuts by mid-October. A crop loss of 30% could be attributed to weevils in an unsprayed orchard. However, adult weevils are very susceptible to both carbaryl and methidathion sprays. In addition, exposure of infested nuts to full sunlight over several weeks kills 100% of larvae. Crops should be surveyed for weevil damage from the 5-10 mm diameter stage until mid-December. Methidathion used as an initial spray for fruitspotting bugs should provide control. Organic growers are advised to sweep infested nuts into mown interrows where solarisation will kill larvae.

Emerging henipaviruses and flying foxes - Conservation and management perspectives

Wildlife populations are affected by a series of emerging diseases, some of which pose a significant threat to their conservation. They can also be reservoirs of pathogens that threaten domestic animal and human health. In this paper, we review the ecology of two viruses that have caused significant disease in domestic animals and humans and are carried by wild fruit bats in Asia and Australia. The first, Hendra virus, has caused disease in horses and/or humans in Australia every five years since it first emerged in 1994. Nipah virus has caused a major outbreak of disease in pigs and humans in Malaysia in the late 1990s and has also caused human mortalities in Bangladesh annually since 2001. Increased knowledge of fruit bat population dynamics and disease ecology will help improve our understanding of processes driving the emergence of diseases from bats. For this, a transdisciplinary approach is required to develop appropriate host management strategies that both maximise the conservation of bat populations as well as minimise the risk of disease outbreaks in domestic animals and humans.

Henipaviruses: Emerging Paramyxoviruses Associated with Fruit Bats

Two related, novel, zoonotic paramyxoviruses have been described recently. Hendra virus was first reported in horses and thence humans in Australia in 1994; Nipah virus was first reported in pigs and thence humans in Malaysia in 1998. Human cases of Nipah virus infection, apparently unassociated with infection in livestock, have been reported in Bangladesh since 2001. Species of fruit bats (genus Pteropus ) have been identified as natural hosts of both agents. Anthropogenic changes (habitat loss, hunting) that have impacted the population dynamics of Pteropus species across much of their range are hypothesised to have facilitated emergence. Current strategies for the management of henipaviruses are directed at minimising contact with the natural hosts, monitoring identified intermediate hosts, improving biosecurity on farms, and better disease recognition and diagnosis. Investigation of the emergence and ecology of henipaviruses warrants a broad, cross-disciplinary ecosystem health approach that recognises the critical linkages between human activity, ecological change, and livestock and human health.

Bats: Important reservoir hosts of emerging viruses

Bats (order Chiroptera, suborders Megachiroptera and Microchiroptera) are abundant, diverse, and geographically widespread. These mammals provide us with resources, but their importance is minimized and many of their populations and species are at risk, even threatened or endangered. Some of their characteristics (food choices, colonial or solitary nature, population structure, ability to fly, seasonal migration and daily movement patterns, torpor and hibernation, life span, roosting behaviors, ability to echolocate, virus susceptibility) make them exquisitely suitable hosts of viruses and other disease agents. Bats of certain species are well recognized as being capable of transmitting rabies virus, but recent observations of outbreaks and epidemics of newly recognized human and livestock diseases caused by viruses transmitted by various megachiropteran and microchiropteran bats have drawn attention anew to these remarkable mammals. This paper summarizes information regarding chiropteran characteristics and information regarding 66 viruses that have been isolated from bats. From these summaries, it is clear that we do not know enough about bat biology, that we are doing too little in terms of bat conservation, and that there remain a multitude of questions regarding the role of bats in disease emergence.

Emerging Viruses: Coming in on a Wrinkled Wing and a Prayer

The role that bats have played in the emergence of several new infectious diseases has been under review. Bats have been identified as the reservoir hosts of newly emergent viruses such as Nipah virus, Hendra virus, and severe acute respiratory syndrome–like coronaviruses. This article expands on recent findings about bats and viruses and their relevance to human infections. It briefly reviews the history of chiropteran viruses and discusses their emergence in the context of geography, phylogeny, and ecology. The public health and trade impacts of several outbreaks are also discussed. Finally, we attempt to predict where, when, and why we may see the emergence of new chiropteran viruses.

Scenario analysis of alternative vegetation management options on the greenhouse gas budget of two grazing businesses in north-eastern Australia

The emerging carbon economy will have a major impact on grazing businesses because of significant livestock methane and land-use change emissions. Livestock methane emissions alone account for similar to 11% of Australia's reported greenhouse gas emissions. Grazing businesses need to develop an understanding of their greenhouse gas impact and be able to assess the impact of alternative management options. This paper attempts to generate a greenhouse gas budget for two scenarios using a spread sheet model. The first scenario was based on one land-type '20-year-old brigalow regrowth' in the brigalow bioregion of southern-central Queensland. The 50 year analysis demonstrated the substantially different greenhouse gas outcomes and livestock carrying capacity for three alternative regrowth management options: retain regrowth (sequester 71.5 t carbon dioxide equivalents per hectare, CO2-e/ha), clear all regrowth (emit 42.8 t CO2-e/ha) and clear regrowth strips (emit 5.8 t CO2-e/ha). The second scenario was based on a 'remnant eucalypt savanna-woodland' land type in the Einasleigh Uplands bioregion of north Queensland. The four alternative vegetation management options were: retain current woodland structure (emit 7.4 t CO2-e/ha), allow woodland to thicken increasing tree basal area (sequester 20.7 t CO2-e/ha), thin trees less than 10 cm diameter (emit 8.9 t CO2-e/ha), and thin trees <20 cm diameter (emit 12.4 t CO2-e/ha). Significant assumptions were required to complete the budgets due to gaps in current knowledge on the response of woody vegetation, soil carbon and non-CO2 soil emissions to management options and land-type at the property scale. The analyses indicate that there is scope for grazing businesses to choose alternative management options to influence their greenhouse gas budget. However, a key assumption is that accumulation of carbon or avoidance of emissions somewhere on a grazing business (e.g. in woody vegetation or soil) will be recognised as an offset for emissions elsewhere in the business (e.g. livestock methane). This issue will be a challenge for livestock industries and policy makers to work through in the coming years.

Tadpole mouthpart depigmentation as an accurate indicator of chytridiomycosis, an emerging disease of amphibians

Chytridiomycosis is an emerging infectious disease of amphibians caused by the fungal pathogen Batrachochytrium dendrobatidis, and its role in causing population declines and species extinctions worldwide has created an urgent need for methods to detect it. Several reports indicate that in anurans chytridiomycosis can cause the depigmentation of tadpole tnouthparts, but the accuracy of using depigmentation to determine disease status remains uncertain. Our objective was to determine for the Mountain Yellow-legged Frog (Rana muscosa) whether visual inspections of the extent of tadpole mouthpart depigmentation could be used to accurately categorize individual tadpoles or R. muscosa populations as B. dendrobatidis-positive or negative. This was accomplished by assessing the degree of mouthpart depigmentation in tadpoles of known disease status (based on PCR assays). The depigmentation of R. muscosa tadpole mouthparts was associated with the presence of B. dendrobatidis, and this association was particularly strong for upper jaw sheaths. Using a rule that classifies tadpoles with upper jaw sheaths that are 100% pigmented as uninfected and those with jaw sheaths that are <100% pigmented as infected resulted in the infection status of 86% of the tadpoles being correctly classified. By applying this rule to jaw sheath pigmentation scores averaged across all tadpoles inspected per site, we were able to correctly categorize the infection status of 92% of the study populations. Similar research on additional anurans is critically needed to determine how broadly applicable our results for R. muscosa are to other species.

Bats and Emerging Zoonoses: Henipaviruses and SARS.

Nearly 75% of all emerging infectious diseases (EIDs) that impact or threaten human health are zoonotic. The majority have spilled from wildlife reservoirs, either directly to humans or via domestic animals. The emergence of many can be attributed to predisposing factors such as global travel, trade, agricultural expansion, deforestation habitat fragmentation, and urbanization; such factors increase the interface and or the rate of contact between human, domestic animal, and wildlife populations, thereby creating increased opportunities for spillover events to occur. Infectious disease emergence can be regarded as primarily an ecological process. The epidemiological investigation of EIDs associated with wildlife requires a trans-disciplinary approach that includes an understanding of the ecology of the wildlife species, and an understanding of human behaviours that increase risk of exposure. Investigations of the emergence of Nipah virus in Malaysia in 1999 and severe acute respiratory syndrome (SARS) in China in 2003 provide useful case studies. The emergence of Nipah virus was associated with the increased size and density of commercial pig farms and their encroachment into forested areas. The movement of pigs for sale and slaughter in turn led to the rapid spread of infection to southern peninsular Malaysia, where the high-density, largely urban pig populations facilitated transmission to humans. Identifying the factors associated with the emergence of SARS in southern China requires an understanding of the ecology of infection both in the natural reservoir and in secondary market reservoir species. A necessary extension of understanding the ecology of the reservoir is an understanding of the trade, and of the social and cultural context of wildlife consumption. Emerging infectious diseases originating from wildlife populations will continue to threaten public health. Mitigating and managing the risk requires an appreciation of the connectedness between human, livestock and wildlife health, and of the factors and processes that disrupt the balance.

Eradication of invasive species: progress and emerging issues in the 21st century

At an international conference on the eradication of invasive species, held in 2001, Simberloff (2002) noted some past successes in eradication—from the global eradication of smallpox (Fenner et al. 1988) to the many successful eradications of populations (mostly mammals) from small islands (e.g. Veitch and Bell 1990; Burbidge and Morris 2002). However, he cautioned that we needed to be more ambitious and aim higher if we are to prevent and reverse the growing threat of the homogenization of global biodiversity. In this chapter we review how the management strategy of eradication—the permanent removal of entire discrete populations—has contributed to the stretch in goals advocated by Simberloff. We also discuss impediments to eradication success, and summarize how some of the lessons learnt during this process have contributed to the other strategies (prevention and sustained control) that are required to manage the wider threat posed by invasive alien species. We concentrate on terrestrial vertebrates and weeds (our areas of expertise), but touch on terrestrial invertebrates and marine and freshwater species in the discussion on emerging issues, to illustrate some of the different constraints these taxa and habitats impose on the feasibility of eradication.

Variation in ecophysiology and carbon economy of invasive and native woody vines of riparian zones in south-eastern Queensland

Exotic and invasive woody vines are major environmental weeds of riparian areas, rainforest communities and remnant natural vegetation in coastal eastern Australia, where they smother standing vegetation, including large trees, and cause canopy collapse. We investigated, through glasshouse resource manipulative experiments, the ecophysiological traits that might facilitate faster growth, better resource acquisition and/or utilization and thus dominance of four exotic and invasive vines of South East Queensland, Australia, compared with their native counterparts. Relative growth rate was not significantly different between the two groups but water use efficiency (WUE) was higher in the native species while the converse was observed for light use efficiency (quantum efficiency, AQE) and maximum photosynthesis on a mass basis (Amax mass). The invasive species, as a group, also exhibited higher respiration load, higher light compensation point and higher specific leaf area. There were stronger correlations of leaf traits and greater structural (but not physiological) plasticity in invasive species than in their native counterparts. The scaling coefficients of resource use efficiencies (WUE, AQE and respiration efficiency) as well as those of fitness (biomass accumulated) versus many of the performance traits examined did not differ between the two species-origin groups, but there were indications of significant shifts in elevation (intercept values) and shifts along common slopes in many of these relationships – signalling differences in carbon economy (revenue returned per unit energy invested) and/or resource usage. Using ordination and based on 14 ecophysiological attributes, a fair level of separation between the two groups was achieved (51.5% explanatory power), with AQE, light compensation point, respiration load, WUE, specific leaf area and leaf area ratio, in decreasing order, being the main drivers. This study suggests similarity in trait plasticity, especially for physiological traits, but there appear to be fundamental differences in carbon economy and resource conservation between native and invasive vine species.

DAQ00096 - Emerging Foliar Wheat Disease Issues in the Northern Region

The emerging disease program seeks to gain information on the distribution of cereal pathogens\pathotypes and potential for outbreaks across the norther region and options for their control. It is looking for an improved understanding of varietal (APR) reaction to stripe rust (YR) in prevailing weather conditions and in the face of climate change. Replicated field trials are used in the evaluation of varietal, cultural and chemical management of YR. Best management practice packages are disseminated to stake holders, including a YR predictive tool.

Current and emerging screening methods to identify post-head-emergence frost adaptation in wheat and barley

Cereal crops can suffer substantial damage if frosts occur at heading. Identification of post-head-emergence frost (PHEF) resistance in cereals poses a number of unique and difficult challenges. Many decades of research have failed to identify genotypes with PHEF resistance that could offer economically significant benefit to growers. Research and breeding gains have been limited by the available screening systems. Using traditional frost screening systems, genotypes that escape frost injury in trials due to spatial temperature differences and/or small differences in phenology can be misidentified as resistant. We believe that by improving techniques to minimize frost escapes, such ofalse-positive' results can be confidently identified and eliminated. Artificial freezing chambers or manipulated natural frost treatments offer many potential advantages but are not yet at the stage where they can be reliably used for frost screening in breeding programmes. Here we describe the development of a novel photoperiod gradient method (PGM) that facilitates screening of genotypes of different phenology under natural field frosts at matched developmental stages. By identifying frost escapes and increasing the efficiency of field screening, the PGM ensures that research effort can be focused on finding genotypes with improved PHEF resistance. To maximize the likelihood of identifying PHEF resistance, we propose that the PGM form part of an integrated strategy to (i) source germplasm;(ii) facilitate high throughput screening; and (iii) permit detailed validation. PGM may also be useful in other studies where either a range of developmental stages and/or synchronized development are desired.

Eriophyid mites on spotted gums: population and histological damage studies of an emerging pest

A suite of co-occurring eriophyid mite species are significant pests in subtropical Australia, causing severe discolouration, blistering, necrosis and leaf loss to one of the region's most important hardwood species, Corymbia citriodora subsp. variegata (F. Muell.) K. D. Hill & L. A. S. Johnson (Myrtaceae). In this study, we examined mite population dynamics and leaf damage over a 1-year period in a commercial plantation of C. citriodora subsp. variegata. Our aims were to link the incidence and severity of mite damage, and mite numbers, to leaf physical traits (moisture content and specific leaf weight (SLW)); to identify any seasonal changes in leaf surface occupancy (upper vs. lower lamina); and host tree canopy strata (upper, mid or lower canopy). We compared population trends with site rainfall, temperature and humidity. We also examined physical and anatomical changes in leaf tissue in response to mite infestation to characterize the plants' physiological reaction to feeding, and how this might affect photosynthesis. Our main findings included positive correlations with leaf moisture content and mite numbers and with mite numbers and damage severity. Wet and dry leaf mass and SLW were greater for damaged tissue than undamaged tissue. Mites were distributed equally throughout the canopy and on both leaf surfaces. No relationships with climatic factors were found. Damage symptoms occurred equally and were exactly mirrored on both leaf surfaces. Mite infestation increased the overall epidermal thickness and the number and size of epidermal cells and was also associated with a rapid loss of chloroplasts from mesophyll cells beneath damage sites. The integrity of the stomatal complex was severely compromised in damaged tissues. These histological changes suggest that damage by these mites will negatively impact the photosynthetic efficiency of susceptible plantation species.

Eriophyid mites on spotted gums: population and histological damage studies of an emerging pest

A suite of co-occurring eriophyid mite species are significant pests in subtropical Australia, causing severe discolouration, blistering, necrosis and leaf loss to one of the region's most important hardwood species, Corymbia citriodora subsp. variegata (F. Muell.) K. D. Hill & L. A. S. Johnson (Myrtaceae). In this study, we examined mite population dynamics and leaf damage over a 1-year period in a commercial plantation of C. citriodora subsp. variegata. Our aims were to link the incidence and severity of mite damage, and mite numbers, to leaf physical traits (moisture content and specific leaf weight (SLW)); to identify any seasonal changes in leaf surface occupancy (upper vs. lower lamina); and host tree canopy strata (upper, mid or lower canopy). We compared population trends with site rainfall, temperature and humidity. We also examined physical and anatomical changes in leaf tissue in response to mite infestation to characterize the plants' physiological reaction to feeding, and how this might affect photosynthesis. Our main findings included positive correlations with leaf moisture content and mite numbers and with mite numbers and damage severity. Wet and dry leaf mass and SLW were greater for damaged tissue than undamaged tissue. Mites were distributed equally throughout the canopy and on both leaf surfaces. No relationships with climatic factors were found. Damage symptoms occurred equally and were exactly mirrored on both leaf surfaces. Mite infestation increased the overall epidermal thickness and the number and size of epidermal cells and was also associated with a rapid loss of chloroplasts from mesophyll cells beneath damage sites. The integrity of the stomatal complex was severely compromised in damaged tissues. These histological changes suggest that damage by these mites will negatively impact the photosynthetic efficiency of susceptible plantation species.