Root-lesion nematodes (Pratylenchus thornei and P. neglectus): A review of recent progress in managing a significant pest of grain crops in northern Australia

Two species of root-lesion nematode (predominantly Pratylenchus thornei but also P. neglectus) are widespread pathogens of wheat and other crops in Australia's northern grain belt, a subtropical region with deep, fertile clay soils and a summer-dominant rainfall pattern. Losses in grain yield from P. thornei can be as high as 70% for intolerant wheat cultivars. This review focuses on research which has led to the development of effective integrated management programs for these nematodes. It highlights the importance of correct identification in managing Pratylenchus species, reviews the plant breeding work done in developing tolerant and resistant cultivars, outlines the methods used to screen for tolerance and resistance, and discusses how planned crop sequencing with tolerant and partially resistant wheat cultivars, together with crops such as sorghum, sunflower, millets and canaryseed, can be used to reduce nematode populations and limit crop damage. The declining levels of soil organic matter in cropped soils are also discussed with reference to their effect on soil health and biological suppression of root-lesion nematodes.

Remote sensing of nitrogen and water stress in wheat

Nitrogen (N) is the largest agricultural input in many Australian cropping systems and applying the right amount of N in the right place at the right physiological stage is a significant challenge for wheat growers. Optimizing N uptake could reduce input costs and minimize potential off-site movement. Since N uptake is dependent on soil and plant water status, ideally, N should be applied only to areas within paddocks with sufficient plant available water. To quantify N and water stress, spectral and thermal crop stress detection methods were explored using hyperspectral, multispectral and thermal remote sensing data collected at a research field site in Victoria, Australia. Wheat was grown over two seasons with two levels of water inputs (rainfall/irrigation) and either four levels (in 2004; 0, 17, 39 and 163 kg/ha) or two levels (in 2005; 0 and 39 kg/ha N) of nitrogen. The Canopy Chlorophyll Content Index (CCCI) and modified Spectral Ratio planar index (mSRpi), two indices designed to measure canopy-level N, were calculated from canopy-level hyperspectral data in 2005. They accounted for 76% and 74% of the variability of crop N status, respectively, just prior to stem elongation (Zadoks 24). The Normalised Difference Red Edge (NDRE) index and CCCI, calculated from airborne multispectral imagery, accounted for 41% and 37% of variability in crop N status, respectively. Greater scatter in the airborne data was attributable to the difference in scale of the ground and aerial measurements (i.e., small area plant samples against whole-plot means from imagery). Nevertheless, the analysis demonstrated that canopy-level theory can be transferred to airborne data, which could ultimately be of more use to growers. Thermal imagery showed that mean plot temperatures of rainfed treatments were 2.7 °C warmer than irrigated treatments (P < 0.001) at full cover. For partially vegetated fields, the two-Dimensional Crop Water Stress Index (2D CWSI) was calculated using the Vegetation Index-Temperature (VIT) trapezoid method to reduce the contribution of soil background to image temperature. Results showed rainfed plots were consistently more stressed than irrigated plots. Future work is needed to improve the ability of the CCCI and VIT methods to detect N and water stress and apply both indices simultaneously at the paddock scale to test whether N can be targeted based on water status. Use of these technologies has significant potential for maximising the spatial and temporal efficiency of N applications for wheat growers. ‘Ground–breaking Stuff’- Proceedings of the 13th Australian Society of Agronomy Conference, 10-14 September 2006, Perth, Western Australia.

Architectural modelling of maize under water stress

Two field experiments using maize (Pioneer 31H50) and three watering regimes [(i) irrigated for the whole crop cycle, until anthesis, (ii) not at all (experiment 1) and (iii) fully irrigated and rain grown for the whole crop cycle (experiment 2)] were conducted at Gatton, Australia, during the 2003-04 season. Data on crop ontogeny, leaf, sheath and internode lengths and leaf width, and senescence were collected at 1- to 3-day intervals. A glasshouse experiment during 2003 quantified the responses of leaf shape and leaf presentation to various levels of water stress. Data from experiment 1 were used to modify and parameterise an architectural model of maize (ADEL-Maize) to incorporate the impact of water stress on maize canopy characteristics. The modified model produced accurate fitted values for experiment 1 for final leaf area and plant height, but values during development for leaf area were lower than observed data. Crop duration was reasonably well fitted and differences between the fully irrigated and rain-grown crops were accurately predicted. Final representations of maize crop canopies were realistic. Possible explanations for low values of leaf area are provided. The model requires further development using data from the glasshouse study and before being validated using data from experiment 2 and other independent data. It will then be used to extend functionality in architectural models of maize. With further research and development, the model should be particularly useful in examining the response of maize production to water stress including improved prediction of total biomass and grain yield. This will facilitate improved simulation of plant growth and development processes allowing investigation of genotype by environment interactions under conditions of suboptimal water supply.

Insecticide resistance and implications for future aphid management in Australian grains and pastures: A review

Aphids can cause substantial damage to cereals, oilseeds and legumes through direct feeding and through the transmission of plant pathogenic viruses. Aphid-resistant varieties are only available for a limited number of crops. In Australia, growers often use prophylactic sprays to control aphids, but this strategy can lead to non-target effects and the development of insecticide resistance. Insecticide resistance is a problem in one aphid pest of Australian grains in Australia, the green peach aphid (Myzus persicae). Molecular analyses of field-collected samples demonstrate that amplified E4 esterase resistance to organophosphate insecticides is widespread in Australian grains across Australia. Knockdown resistance to pyrethroids is less abundant, but has an increased frequency in areas with known frequent use of these insecticides. Modified acetylcholinesterase resistance to dimethyl carbamates, such as pirimicarb, has not been found in Australia, nor has resistance to imidacloprid. Australian grain growers should consider control options that are less likely to promote insecticide resistance, and have reduced impacts on natural enemies. Research is ongoing in Australia and overseas to provide new strategies for aphid management in the future.

Host plant resistance in grain crops and prospects for invertebrate pest management in Australia: An overview

An integrated pest management (IPM) approach that relies on an array of tactics is adopted commonly in response to problems with pesticide-based production in many agricultural systems. Host plant resistance is often used as a fundamental component of an IPM system because of the generally compatible, complementary role that pest-resistant crops play with other tactics. Recent research and development in the resistance of legumes and cereals to aphids, sorghum midge resistance, and the resistance of canola varieties to mite and insect pests have shown the prospects of host plant resistance for developing IPM strategies against invertebrate pests in Australian grain crops. Furthermore, continuing advances in biotechnology provide the opportunity of using transgenic plants to enhance host plant resistance in grains.

The climate change risk management matrix for the grazing industry of northern Australia

The complexity, variability and vastness of the northern Australian rangelands make it difficult to assess the risks associated with climate change. In this paper we present a methodology to help industry and primary producers assess risks associated with climate change and to assess the effectiveness of adaptation options in managing those risks. Our assessment involved three steps. Initially, the impacts and adaptation responses were documented in matrices by ‘experts’ (rangeland and climate scientists). Then, a modified risk management framework was used to develop risk management matrices that identified important impacts, areas of greatest vulnerability (combination of potential impact and adaptive capacity) and priority areas for action at the industry level. The process was easy to implement and useful for arranging and analysing large amounts of information (both complex and interacting). Lastly, regional extension officers (after minimal ‘climate literacy’ training) could build on existing knowledge provided here and implement the risk management process in workshops with rangeland land managers. Their participation is likely to identify relevant and robust adaptive responses that are most likely to be included in regional and property management decisions. The process developed here for the grazing industry could be modified and used in other industries and sectors. By 2030, some areas of northern Australia will experience more droughts and lower summer rainfall. This poses a serious threat to the rangelands. Although the impacts and adaptive responses will vary between ecological and geographic systems, climate change is expected to have noticeable detrimental effects: reduced pasture growth and surface water availability; increased competition from woody vegetation; decreased production per head (beef and wool) and gross margin; and adverse impacts on biodiversity. Further research and development is needed to identify the most vulnerable regions, and to inform policy in time to facilitate transitional change and enable land managers to implement those changes.

Can feral pig harvesting and co-ordinated control reduce damage to grain crops?

Commercial and recreational harvesting of pigs is often encouraged by pest managers because it is essentially a ‘free’ reduction in pest density. However, the reduction in numbers may provide minimal damage mitigation and may be inappropriately allocated in space and time. Additionally, more effective control (e.g. baiting) may not occur because of the incorrect perception that harvesting is effective or because pigs are valued for recreational use.

Implementation of a modified CVSD coder

This paper describes the implementation of the modified continuously variable slope delta modulator (MCVSD), in which the basic step size δ0 is made to vary as a function of input signal level. The information needed to carry out this is extracted at the local decoder output so that the coder and the decoder track each other. The result is a significant improvement in the dynamic range (about 15dB) as compared to CVSD coder without degrading the peak signal to noise ratio.

Selecting replacements for invasive plants to support frugivores in highly modified sites: a case study focusing on Lantana camara

Invasive plants are regarded as a major threat to biodiversity worldwide. Yet, in some cases, invasive plants now perform important ecological functions. For example, fleshy-fruited invasive plants provide food that supports indigenous frugivore populations. How can the disparate goals of conservation versus invasive weed control be managed? We suggest using the fruit characteristics of the invasive plant to select replacement indigenous plants that are functionally similar from the perspective of frugivores. These could provide replacement food resources at sites where plants with these characteristics are part of the goal plant community and where such plants would not otherwise regenerate. Replacement plants could also redirect seed dispersal processes to favour indigenous, rather than invasive, plant species. We investigated the utility of this approach by ranking all indigenous fleshy-fruited plant species from a region using a simple model that scored species based upon measures of fruit phenology, morphology, conspicuousness and accessibility relative to a target invasive species, Lantana (Lantana camara). The model successfully produced high scores for indigenous plant species that were used by more of the frugivores of Lantana than a random selection of plants, suggesting that this approach warrants further investigation.

Micropropagation of vegetatively propagated crops: accelerating release of new cultivars and providing an important source of clean planting material

Micropropagation is unequalled for the rapid clonal propagation of improved cultivars from several Australian breeding programmes. This has been particularly true of the pineapple breeding programme, but it has also found an important role in the strawberry breeding programme where high-health mother stock is of paramount concern. In the banana and ginger industries, while access to new cultivars has been of importance, micropropagation has been adopted by the industry to ensure that planting materials are free from serious pests and diseases. Bananas can be used as planting material as early as the first generation ex vitro and is responsible for the establishment of laboratories and nurseries specializing in the production of pathogen-tested plants. The ginger industry, on the other hand, has used micropropagated plants as a source of disease and pest-free stock to establish a clean 'seed' scheme based on the production of conventional planting material.

Diseases of fruit crops in Australia.

Diseases of Fruit Crops in Australia is the new standard reference in applied plant pathology in Australia covering important diseases affecting the broad range of fruit and nut crops grown throughout Australia. It is an essential tool for growers, horticulturists, crop consultants, research scientists, plant pathologists, quarantine officers, agribusiness representatives, pest management personnel, educators and students. The book is generously illustrated with high quality colour images to help diagnose diseases. It explains how to identify and manage each disease, describing the symptoms, its importance, the source of infection and spread, and control measures. Based on the highly regarded 1993 edition of Diseases of Fruit Crops, this new work updates management practices that have evolved since then. Importantly, it contains the latest information on diseases that have recently emerged in Australia as well as exotic diseases that are biosecurity threats to Australian fruit and nut production.

An investigation of solid adamantane by a modified isothermal-isobaric ensemble Monte Carlo simulation

Isothermal-isobaric ensemble Monte Carlo simulation studies of adamantane have been carried out at different temperatures. Thermodynamic properties and radial distribution functions calculated by employing a simple potential model based on sitesite interactions show good agreement with experiment and suggest that the solid is orientationally disordered at high temperatures.

Adenoviral Gene Therapy for Advanced Head and Neck Cancer

Advanced stage head and neck cancers (HNC) with distant metastasis, as well as prostate cancers (PC), are devastating diseases currently lacking efficient treatment options. One promising developmental approach in cancer treatment is the use of oncolytic adenoviruses, especially in combination therapy with conventional cancer therapies. The safety of the approach has been tested in many clinical trials. However, antitumor efficacy needs to be improved in order to establish oncolytic viruses as a viable treatment alternative. To be able to test in vivo the effects on anti-tumor efficiency of a multimodal combination therapy of oncolytic adenoviruses with the standard therapeutic combination of radiotherapy, chemotherapy and Cetuximab monoclonal antibody (mAb), a xenograft HNC tumor model was developed. This model mimics the typical clinical situation as it is initially sensitive to cetuximab, but resistance develops eventually. Surprisingly, but in agreement with recent findings for chemotherapy and radiotherapy, a higher proportion of cells positive for HNC cancer stem cell markers were found in the tumors refractory to cetuximab. In vitro as well as in vivo results found in this study support the multimodal combination therapy of oncolytic adenoviruses with chemotherapy, radiotherapy and monoclonal antibody therapy to achieve increased anti-tumor efficiency and even complete tumor eradication with lower treatment doses required. In this study, it was found that capsid modified oncolytic viruses have increased gene transfer to cancer cells as well as an increased antitumor effect. In order to elucidate the mechanism of how oncolytic viruses promote radiosensitization of tumor cells in vivo, replicative deficient viruses expressing several promising radiosensitizing viral proteins were tested. The results of this study indicated that oncolytic adenoviruses promote radiosensitization by delaying the repair of DNA double strand breaks in tumor cells. Based on the promising data of the first study, two tumor double-targeted oncolytic adenoviruses armed with the fusion suicide gene FCU1 or with a fully human mAb specific for human Cytotoxic T Lymphocyte-Associated Antigen 4 (CTLA-4) were produced. FCU1 encodes a bifunctional fusion protein that efficiently catalyzes the direct conversion of 5-FC, a relatively nontoxic antifungal agent, into the toxic metabolites 5-fluorouracil and 5-fluorouridine monophosphate, bypassing the natural resistance of certain human tumor cells to 5-fluorouracil. Anti-CTLA4 mAb promotes direct killing of tumor cells via apoptosis and most importantly immune system activation against the tumors. These armed oncolytic viruses present increased anti-tumor efficacy both in vitro and in vivo. Furthermore, by taking advantage of the unique tumor targeted gene transfer of oncolytic adenoviruses, functional high tumor titers but low systemic concentrations of the armed proteins were generated. In addition, supernatants of tumor cells infected with Ad5/3-24aCTLA4, which contain anti-CTLA4 mAb, were able to effectively immunomodulate peripheral blood mononuclear cells (PBMC) of cancer patients with advanced tumors. -- In conclusion, the results presented in this thesis suggest that genetically engineered oncolytic adenoviruses have great potential in the treatment of advanced and metastatic HNC and PC.

New Modified Dipping Method Using 4-hexylresorcinol for Preventing Blackspot Formation in Prawns.

Industry acceptance of alternative sulphite treatments for preventing blackspot in prawns is limited. This study demonstrated that dipping prawns (Penaeus monodon and Fenneropenaeus merguiensis) in a less concentrated solution for longer times provides better control of blackspot formation than the recommended 2 minute dip in 50 mg/L 4-hexylresorcinol. Protection improved as modified dipping times and solution concentrations increased. Blackspot protection provided by most of the modified dip methods was more effective than a 1 minute dip in 1% sodium metabisulphite. The recommended 2 minute dip method should be limited to 125 kg when used on consecutive 25-kg batches of prawns. Yields increased by less than 10% even after 72-hour exposure in the modified dip. The new dipping method meets most international residue standards when applying the modified treatments evaluated.

Identification of insects, spiders and mites in vegetable crops. Workshop Manual, 2nd edition

Accurate and confident identification of the insects, spiders and mites in vegetable crops is the first step towards successful management of pests and natural enemies. It is an essential prerequisite for crop monitoring, which is the backbone of an effective pest management program. This workshop manual and trainer's handbook were compiled as part of an insect, spider and mite identification program for Australian vegetable growers. The workshop training is designed to help growers to: • know how to collect and preserve insects for identification • be able to classify most common insects (particularly those of horticultural significance) into broad groups • appreciate the importance of these groups in pest, predator and parasite identification and management • collect and classify some insect pests, predators and parasites of horticultural importance.