New annual and short-lived perennial pasture legumes for Australian agriculture--15 years of revolution

Fifteen years ago subterranean clover (Trifolium subterraneum) and annual medics (Medicago spp.) dominated annual pasture legume sowings in southern Australia, while limited pasture legume options existed for cropping areas of subtropical Australia. Since then a number of sustainability and economic challenges to existing farming systems have emerged, exposing shortcomings in these species and the lack of legume biodiversity. Public breeding institutions have responded to these challenges by developing 58 new annual and short-lived perennial pasture legumes with adaptation to both existing and new farming systems. This has involved commercialisation of new species and overcoming deficiencies in traditional species. Traits incorporated in legumes of Mediterranean Basin origin for the Mediterranean, temperate and southern subtropical climates of Australia include deeper root systems, protection from false breaks (germination-inducing rainfall events followed by death from drought), a range of hardseed levels, acid-soil tolerant root nodule symbioses, tolerance to pests and diseases and provision of lower cost seed through ease of seed harvesting and processing. Ten new species, French serradella (Ornithopus sativus), biserrula (Biserrula pelecinus), sulla (Hedysarum coronarium), gland (Trifolium glanduliferum), arrowleaf (Trifolium vesiculosum), eastern star (Trifolium dasyurum) and crimson (Trifolium incarnatum) clovers and sphere (Medicago sphaerocarpos), button (Medicago orbicularis) and hybrid disc (Medicago tornata x Medicago littoralis) medics have been commercialised. Improved cultivars have also been developed of subterranean (T. subterraneum), balansa (Trifolium michelianum), rose (Trifolium hirtum), Persian (Trifolium resupinatum) and purple (Trifolium purpureum) clovers, burr (Medicago polymorpha), strand (M. littoralis), snail (Medicago scutellata) and barrel (Medicago truncatula) medics and yellow serradella (Ornithopus compressus). New tropical legumes for pasture phases in subtropical cropping areas include butterfly pea (Clitoria ternatea), burgundy bean (Macroptilium bracteatum) and perennial lablab (Lablab purpureus). Other species and cultivars of Mediterranean species are likely to be released soon. The contributions of genetic resources, rhizobiology, pasture ecology and agronomy, plant pathology, entomology, plant chemistry and animal science have been paramount to this success. A farmer survey in Western Australia has shown widespread adoption of the new pasture legumes, while adoption of new tropical legumes has also been high in cropping areas of the subtropics. This trend is likely to increase due to the increasing cost of inorganic nitrogen, the need to combat herbicide-resistant crop weeds and improved livestock prices. Mixtures of these legumes allows for more robust pastures buffered against variable seasons, soils, pests, diseases and management decisions. This paper discusses development of the new pasture legumes, their potential use and deficiencies in the current suite. 'Ground–breaking Stuff’- Proceedings of the 13th Australian Society of Agronomy Conference, 10-14 September 2006, Perth, Western Australia.

Approaches to selecting native plant replacements for fleshy-fruited invasive species

Invasive plants are a serious threat to biodiversity. Yet, in some cases, they may play an important ecological role in heavily modified landscapes, such as where fleshy-fruited invasive plants support populations of native frugivores. How can such conservation conflicts be managed? We advocate an approach in which native fleshy-fruited plants are ranked on their ability to provide the fruit food resources for native frugivores currently being provided by invasive plants. If these native taxa are preferentially used, where ecologically appropriate, in plantings for restoration and in park and garden settings, they could help support native frugivore populations in the event of extensive invasive plant control. We develop and critically examine six approaches to selecting candidate native plant taxa: a multivariate approach based on the frugivore assemblage, a scoring model, and several multivariate approaches (including trait combinations having the greatest correlation with the diet of the native frugivore assemblage) based on the functional traits of fruit morphology, phenology, conspicuousness, and accessibility. To illustrate these approaches, we use a case study with Bitou bush (Chrysanthemoides monilifera subsp. rotundata) (Asteraceae), an Australian Weed of National Significance. The model using a dissimilarity value generated from all available traits identified a set of species used by the frugivores of C. monilifera more than null models. A replacement approach using species ranked by either all traits available or the frugivore community appears best suited to guide selection of plants in restoration practice.

Biology of Plant Rhabdoviruses

The Rhabdoviridae, whose members collectively infect invertebrates, animals, and plants, form a large family that has important consequences for human health, agriculture, and wildlife ecology. Plant rhabdoviruses can be separated into the genera Cytorhabdovirus and Nucleorhabdovirus, based on their sites of replication and morphogenesis. This review presents a general overviewof classical and contemporary findings about rhabdovirus ecology, pathology, vector relations, and taxonomy. The genome organization and structure of several recently sequenced nucleorhabdoviruses and cytorhabdoviruses is integrated with new cell biology findings to provide a model for the replication of the two genera. A prospectus outlines the exciting opportunities for future research that will contribute to a more detailed understanding of the biology, biochemistry, replication and host interactions of the plant rhabdoviruses.

Incorporating dugong habitats into the marine protected area design for the Great Barrier Reef Marine Park, Queensland, Australia.

Dugong habitats were considered in the design for the new zoning network for the Great Barrier Reef Marine Park as part of the Representative Areas Program. One of the specific design guidelines developed as part of the biophysical operational principles recommended that 50% of all high priority dugong habitats should be incorporated in the network of no-take areas. The high priority dugong habitat incorporated in no-take protection increased from 1396 to 3476 km2 (or 16.9-42.0% of all identified sites). Although this increase in protection fell short of the recommended 50%, overall the level of protection afforded by the Great Barrier Reef Marine Park Zoning Plan 2003 increased for all the locations identified.

Worldwide phylogeography of the globally invasive plant: Jatropha gossypiifolia

Dhileepan, Raghu and colleagues recently published their paper 'Worldwide phylogeography of the globally invasive plant: Jatropha gossypiifolia' in Proceedings of the 16th Australian Weeds Conference. They used chloroplast microsatellites to establish patterns of phylogeographic structure in the native and introduced range of Jatropha gossypiifolia, and to determine the origin(s) of introductions and the level of genetic diversity present in native and introduced populations. J. gossypiifolia exhibited limited phylogeographic structure in its native range which was best explained by contemporary movement associated with the ornamental plant trade. Multiple introductions from diverse source locations and no reduction in genetic diversity was found in the introduced range which includes Australia, Africa and Asia. These results have implications for our current biocontrol project.

Control of the invasive liana, Hiptage benghalensis

The liana, hiptage (Hiptage benghalensis), is currently invading the wet tropics of northern Queensland and remnant bushland in south-eastern Queensland, Australia. Trials using seven herbicides and three application methods (foliar, basal bark, and cut stump) were undertaken at a site in north Queensland (158 700 hiptage plants ha−1). The foliar-applied herbicides were only effective in controlling the hiptage seedlings. Of the foliar herbicides trialed, dicamba, fluroxypyr, and triclopyr/picloram controlled >75% of the treated seedlings. On the larger plants, the cut stump applications were more effective than the basal bark treatments. Kills of >95% were obtained when the plants were cut close to ground level (5 cm) and treated with herbicides that were mixed with diesel (fluroxypyr and triclopyr/picloram), with water (glyphosate), or were applied neat (picloram). The costings for the cut stump treatment of a hiptage infestation (85 000 plants ha−1), excluding labor, would be $A14 324 ha−1 using picloram and $A5294 ha−1 and $A2676 ha−1, respectively, using glyphosate and fluroxypyr. Foliar application using dicamba for seedling control would cost $A1830 ha−1. The costs range from 2–17 cents per plant depending on the treatment. A lack of hiptage seeds below the soil surface, a high germinability (>98%) of the viable seeds, a low viability (0%) of 2 year old, laboratory-stored fruit, and a seedling density of 0.1 seedlings m−2 12 months after a control program indicate that hiptage might have a short-term seed bank. Protracted recolonization from the seed bank would therefore be unlikely after established seed-producing plants have been controlled.

Management of plant invasions mediated by frugivore interactions

1. Some of the most damaging invasive plants are dispersed by frugivores and this is an area of emerging importance in weed management. It highlights the need for practical information on how frugivores affect weed population dynamics and spread, how frugivore populations are affected by weeds and what management recommendations are available. 2. Fruit traits influence frugivore choice. Fruit size, the presence of an inedible peel, defensive chemistry, crop size and phenology may all be useful traits for consideration in screening and eradication programmes. By considering the effect of these traits on the probability, quality and quantity of seed dispersal, it may be possible to rank invasive species by their desirability to frugivores. Fruit traits can also be manipulated with biocontrol agents. 3. Functional groups of frugivores can be assembled according to broad species groupings, and further refined according to size, gape size, pre- and post-ingestion processing techniques and movement patterns, to predict dispersal and establishment patterns for plant introductions. 4. Landscape fragmentation can increase frugivore dispersal of invasives, as many invasive plants and dispersers readily use disturbed matrix environments and fragment edges. Dispersal to particular landscape features, such as perches and edges, can be manipulated to function as seed sinks if control measures are concentrated in these areas. 5. Where invasive plants comprise part of the diet of native frugivores, there may be a conservation conflict between control of the invasive and maintaining populations of the native frugivore, especially where other threats such as habitat destruction have reduced populations of native fruit species. 6. Synthesis and applications. Development of functional groups of frugivore-dispersed invasive plants and dispersers will enable us to develop predictions for novel dispersal interactions at both population and community scales. Increasingly sophisticated mechanistic seed dispersal models combined with spatially explicit simulations show much promise for providing weed managers with the information they need to develop strategies for surveying, eradicating and managing plant invasions. Possible conservation conflicts mean that understanding the nature of the invasive plant-frugivore interaction is essential for determining appropriate management.

An improved technique for estimating short-term survival of released line-caught fish, and an application comparing barotrauma-relief methods in red emperor (Lutjanus sebae Cuvier 1816).

Promotion of better procedures for releasing undersize fish, advocacy of catch-and-release angling, and changing minimum legal sizes are increasingly being used as tools for sustainable management of fish stocks. However without knowing the proportion of released fish that survive, the conservation value of any of these measures is uncertain. We developed a floating vertical enclosure to estimate short-term survival of released line-caught tropical and subtropical reef-associated species, and used it to compare the effectiveness of two barotrauma-relief procedures (venting and shotline releasing) on red emperor (Lutjanus sebae). Barotrauma signs varied with capture depth, but not with the size of the fish. Fish from the greatest depths (40-52 m) exhibited extreme signs less frequently than did those from intermediate depths (30-40 m), possibly as a result of swim bladder gas being vented externally through a rupture in the body wall. All but two fish survived the experiment, and as neither release technique significantly improved short-term survival of the red emperor over non-treatment we see little benefit in promoting either venting or shotline releasing for this comparatively resilient species. Floating vertical enclosures can improve short-term post-release mortality estimates as they overcome many problems encountered when constraining fish in submerged cages.

Characterising insect plant host relationships facilitates understanding multiple host use

Weed biocontrol relies on host specificity testing, usually carried out under quarantine conditions to predict the future host range of candidate control agents. The predictive power of host testing can be scrutinised directly with Aconophora compressa, previously released against the weed Lantana camara L. (lantana) because its ecology in its new range (Australia) is known and includes the unanticipated use of several host species. Glasshouse based predictions of field host use from experiments designed a posteriori can therefore be compared against known field host use. Adult survival, reproductive output and egg maturation were quantified. Adult survival did not differ statistically across the four verbenaceous hosts used in Australia. Oviposition was significantly highest on fiddlewood (Citharexylum spinosum L.), followed by lantana, on which oviposition was significantly higher than on two varieties of Duranta erecta (‘‘geisha girl’’ and ‘‘Sheena’s gold’’; all Verbenaceae). Oviposition rates across Duranta varieties were not significantly different from each other but were significantly higher than on the two non-verbenaceous hosts (Jacaranda mimosifolia D. Don: Bignoneaceae (jacaranda) and Myoporum acuminatum R. Br.: Myoporaceae (Myoporum)). Production of adult A. compressa was modelled across the hosts tested. The only major discrepancy between model output and their relative abundance across hosts in the field was that densities on lantana in the field were much lower than predicted by the model. The adults may, therefore, not locate lantana under field conditions and/or adults may find lantana but leave after laying relatively few eggs. Fiddlewood is the only primary host plant of A. compressa in Australia, whereas lantana and the others are used secondarily or incidentally. The distinction between primary, secondary and incidental hosts of a herbivore species helps to predict the intensity and regularity of host use by that herbivore. Populations of the primary host plants of a released biological control agent are most likely to be consistently impacted by the herbivore, whereas secondary and incidental host plant species are unlikely to be impacted consistently. As a consequence, potential biocontrol agents should be released only against hosts to which they have been shown to be primarily adapted.

Refining the process of agent selection through understanding plant demography and plant response to herbivory

Understanding plant demography and plant response to herbivory is critical to the selection of effective weed biological control agents. We adopt the metaphor of 'filters' to suggest how agent prioritisation may be improved to narrow our choices down to those likely to be most effective in achieving the desired weed management outcome. Models can serve to capture our level of knowledge (or ignorance) about our study system and we illustrate how one type of modelling approach (matrix models) may be useful in identifying the weak link in a plant life cycle by using a hypothetical and an actual weed example (Parkinsonia aculeata). Once the vulnerable stage has been identified we propose that studying plant response to herbivory (simulated and/or actual) can help identify the guilds of herbivores to which a plant is most likely to succumb. Taking only potentially effective agents through the filter of host specificity may improve the chances of releasing safe and effective agents. The methods we outline may not always lead us definitively to the successful agent(s), but such an empirical, data-driven approach will make the basis for agent selection explicit and serve as testable hypotheses once agents are released.

Relative host plant species use by the lantana biological control agent Aconophora compressa (Membracidae) across its native and introduced ranges

Aconophora compressa Walker (Hemiptera: Membracidae) was released in 1995 against the weed lantana in Australia, and is now found on multiple host plant species. The intensity and regularity at which A. compressa uses different host species was quantified in its introduced Australian range and also its native Mexican range. In Australia, host plants fell into three statistically defined categories, as indicated by the relative rates and intensities at which they were used in the field. Fiddlewood (Citharexylum spinosum L.: Verbenaceae) was used much more regularly and at higher densities than any other host sampled, and alone made up the first group. The second group, lantana (Lantana camara L.: Verbenaceae; pink variety) and geisha girl (Duranta erecta L.: Verbenaceae), were used less regularly and at much lower densities than fiddlewood. The third group, Sheena’s gold (another variety of D. erecta), jacaranda (Jacaranda mimosifolia D. Don: Bignoniaceae) and myoporum (Myoporum acuminatum R. Br.: Myoporaceae), were used infrequently and at even lower densities. In Mexico, the insect was found at relatively low densities on all hosts relative to those in Australia. Densities were highest on L. urticifolia, D. erecta and Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae), which were used at similar rates to one another. It was found also on a few other verbenaceous and non-verbenaceous host species but at even lower densities. The relative rate at which Citharexylum spp. and L. urticifolia were used could not be assessed in Mexico because A. compressa was found on only one plant of each species in areas where these host species co-occurred. The low rate at which A. compressa occurred on fiddlewood in Mexico is likely to be an artefact of the short-term nature of the surveys or differences in the suites of Citharexylum and Lantana species available there. These results provide further incentive to insist on structured and quantified surveys of non-target host use in the native range of potential biological control agents prior to host testing studies in quarantine.

Improved understanding of the damage, ecology, and management of mirids and stinkbugs in Bollgard II

In recent years mirids and stinkbugs have emerged as important sucking pests in cotton. While stinkbugs are causing damage to bolls, mirids are causing damage to seedlings, squares and bolls. With the increasing adoption of Bollgard II and IPM approaches the use of broad-spectrum chemicals to kill Helicoverpa has been reduced and as a result mirids and stinkbugs are building to levels causing damage to bolls later in crop growth stages. Studies on stinkbugs by Dr Moazzem Khan revealed that green vegetable bug (GVB) caused significant boll damage and yield loss. A preliminary study by Dr Khan on mirids revealed that high mirid numbers at later growth stages also caused significant boll damage and that damage caused by mirids and GVB were similar. Mirids and stinkbugs therefore demand greater attention in order to minimise losses caused by these pests and to develop IPM strategies against these pests to enhance gains in IPM that have been made with Bt-transgenic cotton. Progress in this area of research will maintain sustainability and profitability of the Australian cotton industry. Mirid damage at early growth stages of cotton (up to squaring stage) has been studied in detail by Dr Khan. He found that all ages of mirids cause damage to young plants and damage by mirid nymphs is cumulative. Maximum damage occurs when the insect reaches the 4th and 5th nymphal stages. He also found that mirid feeding causes shedding of small and medium squares, and damaged large squares develop as ‘parrot beak’ bolls. Detailed studies at the boll stage, such as which stage of mirids is most damaging or which age boll is most vulnerable to feeding, is lacking. This information is a prerequisite to developing an IPM strategy for the pest in later crop growth stages. Understanding population change of the pest over time in relation to crop development is an important aspect for developing management strategies for the pest which is lacking for mirids in BollgardII. Predators and parasitoids are integral components of any IPM system and play an important part in regulating pest populations. Some generalist predators such as ants, spiders, damsel bugs and assassin bugs are known to predate on mirids. Nothing is known about parasitoids of mirids. Since green mirid (GM), Creontiades dilutus, is indigenous to Australia it is likely that we have one or more parasitoids of this mirid in Australia, but that possibility has not been investigated yet. The impact of the GVB adult parasitoid, Trichopoda giacomelli, has been studied by Dr Khan who found that the fly is established in the released areas and continues to spread. However, to get wider and greater impact, the fly should be released in new locations across the valleys. The insecticides registered for mirids and stinkbugs are mostly non-selective and are extremely disruptive to a wide range of beneficial insects. Use of these insecticides at stage I and II will minimise the impact of existing IPM programs. Therefore less disruptive control tactics including soft chemicals for mirids and stinkbugs are necessary. As with soft chemicals, salt mixtures, biopesticides based on fungal pathogens and attractants based on plant volatiles may be useful tools in managing mirids and stinkbugs with less or no disruption. Dr Khan has investigated salt mixture against mirids and GVB. While salt mixtures are quite effective and less disruptive, they are quite chemical specific. Not all chemicals mixed with salt will give the desired benefit. Therefore further investigation is needed to identify those chemicals that are effective with salt mixture against mirids and 3 of 37 GVB. Dr Caroline Hauxwell of DPI&F is working on fungal pathogen-based biopesticides against mirids and GVB and Drs Peter Gregg and Alice Del Socorro of Australian Cotton CRC are working on plant volatile-based attractants against mirids. Depending on their findings, inclusion of fungal-based biopestcides and plant volatile-based attractants in developing a management system against mirids and stinkbugs in cotton could be an important component of an IPM approach.

CRC50089 Grain Insect Ecology

Resistance to phosphine in target pests threatens market access for Australian grain. While the grains industry is now attempting to develop an effective and sustainable strategy to manage this resistance, action is severely limited by significant gaps in our knowledge of the key ecological factors that influence the development of resistance. There is a need to research this information as a foundation for a rational approach to managing phosphine resistance in the Australian grains industry. Research outcomes: The project has provided critical research methodologies and preliminary data to fill the large gaps in our knowledge of the ecology of two key pests, Rhyzopertha dominica and Tribolium castaneum, and how this may drive the development of phosphine resistance. This information will contribute to the groundwork for future research needed to provide a scientific basis for a rational resistance management strategy.

Short-range resource location by Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) demonstrates a strong preference for fungi associated with cotton seed

Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is a common stored grain pest for which a wide range of suitable resources has been recorded. These beetles are facultatively fungivorous and their resource range may extend to fungi associated with non-grain resources (e.g. cotton seed) and other decaying plant matter. Little is known with respect to fungi in terms of resource location by these beetles in the field. We, therefore, conducted a series of experiments in laboratory arenas, glasshouse cages and the field to determine how beetles respond to grain resources in relation to cotton seed (together with its lint stubble and associated fungal flora). Results from the tests conducted in relatively small arenas and cages in the laboratory and glasshouse reveal that the responses of T. castaneum adults to food resources were twice as strong when walking as when flying (as measured by the proportion of the released beetles that were trapped). Also, a clear preference for linted cotton seeds was evident in walking T. castaneum, especially in small-scale arenas in the laboratory, where at least 60% of beetles released preferred linted cotton seeds over wheat and sorghum. Similarly, in cages (1 m3) they responded five times more strongly to linted cotton seed than to conventional grain resources. However, this pattern was not consistent with those obtained from field trapping over 20 m and the beetles did not show any particular preference to any of the resources tested above. Our results suggest a focus on walking beetles in trapping studies for population estimations and, for developing effective food-based trapping lures, the potential use of active volatiles from the fungi associated with linted cotton seed. © 2012 Elsevier Ltd.