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Rural Industries
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|| Introduction || Project listing|| Project Summaries ||
Pest, weed and disease control costs Australian farmers an estimated $800 million per year in chemical and biological control agents before the addition of application costs.
Yet without their use an estimated one third of the harvest, valued around $3 billion in 1990, would be lost to pests and diseases. While the control of individual pests, weeds or diseases may be beyond the capability of a particular industry it could be within the resource capability of the rural sector as a whole.
RIRDC recognises a need to work closely with other rural industry research funding corporations and research agencies in pest and disease control and to take a lead role in coordinating R&D in some circumstances.
The Corporation believes there is an urgent need to reduce the environmental and social impacts on other industries associated with both chemical and biological pest and disease control.
It also recognises that pests and diseases are part of a biological system themselves, are continually evolving, and therefore will require ongoing attention.
Research Highlights for 1996-97
· Better understanding of the host range of root-knot nematode species to allow more effective non-chemical management strategies to be developed in a wide range of vegetable industries.
· Research into the biological control of mouse plagues.
· Isolation of novel BT toxin strains for controlling insect pests.
· Development of a new generic computer model of modular growth of plants to improve pest and disease management by simulating damage responses in host plants to attacks by pests or pathogens.
· Evaluation of the national capability to effectively diagnose plant diseases and identification of areas of deficiencies.
ROOT-KNOT AND CYST NEMATODES WORKSHOP
Objectives
· To run a two day workshop focussing on the impact, identification and control of root-knot and cyst nematode problems in Australian and New Zealand agriculture.
· To provide a forum for Australasian nematologists to exchange information on the diseases which these species cause.
Background
Root-knot and cyst nematodes cause most of the estimated annual losses of $300-400 million/year attributed to nematode diseases in Australian and New Zealand crops. With declining numbers of experienced nematologists in Australia and New Zealand, it is becoming increasingly important that opportunities be provided for this group of scientists to meet on a discipline basis to exchange information on nematodes and the diseases they cause.
The holding of biennial Australasian Plant Pathology conferences provides an opportunity to hold such workshops in conjunction with them, to take advantage of reduced costs by having the maximum number of participants present (often funded by other sources).
At the last conference, in Hobart in 1993, a similar workshop on root lesion nematodes was funded by GRDC. This workshop brings together a wide range of experts, including those from other fields.
Research
The workshop was structured to allow discussion on:
· Impact of root-knot and cyst nematodes in cropping systems (symptoms, crop loss assessment, density dependent effects)
· Interactions (host-parasite models; interspecific competition, nematode and fungal interactions; interactions between different nematodes)
· Identification (systematics of the Heteroderidae; species separation, intraspecific differentiation and pathotyping systems using molecular markers)
· Control (chemical options, cultural practices, plant resistance).
Practical sessions on identifying the various nematode species were also held.
Outcomes
A very effective workshop was held, which was attended by more than thirty scientists. The workshop provided a valuable opportunity for the limited number of experienced nematologists still employed, to provide advice to the small group of young inexperienced scientists now dealing with nematode diseases.
Implications
At relatively small cost to the Corporation, the discipline of nematology has been given considerable support. Potential new areas of work have been identified and, already, research proposals have been received. Such workshops ought to be supported every three or four years to maintain the impetus of the discipline.
RIRDC Project No: AAN-1A
RESEARCHER: Dr J Curran
ORGANISATION: Australasian Association of Nematologists,
C/o- CSIRO Division of Entomology, PO Box 1700, CANBERRA ACT 2601 PHONE:
02 6246 4294 FAX: 02 6246 4000
RESISTANCE TO BT IN LEPIDOPTEROUS PESTS
Objectives
· To examine the potential for development of resistance to Bt and the possibility of cross resistance to other ICPx (incesticidal crystal proteins) using Helicoverpa armigera as a model.
· To elucidate the mechanism of resistance, and develop resources and techniques required for monitoring and managing resistance to Bt in insect pests.
Background
Bacillus thuringiensis (Bt) is the most widely used microbial insecticide and, as such, plays a major role in reducing our dependence on synthetic chemical insecticides. The development of resistance to Bt detected in some lepidopterous pests poses a significant threat to reducing environmental damage resulting from pesticide use.
Knowledge of such factors as increasing use of Bt sprays and the cloning of a Bt ICP gene into cotton for the control of H. armigera, developing resistance to a Bt ICP, examining the possibility of cross resistance to other Bt ICPs, and elucidating the mechanism(s) underlying resistance, will help to maintain (extend) the life of such a valuable biological insecticide for use in a range of crops.
Research
Various techniques were employed in attempts to select populations of the insect resistant to Bt. Susceptibility (resistance) was estimated in dose-mortality experiments with insects being exposed to ICPs form various sources. This was complemented by studies on progeny from selected genetic crosses, and by the use of EMS metagenesis. Additionally, bioassays were used to compare individual ICPs, and to compare interactions between ICPs to the mid-gut epithelium of insects.
Outcomes
Sixteen Bt ICPs were tested on the insect, but only four had any significant effect. However, as there is little difference between these, it is likely that only one offers an alternative to the widely used form Cry1Ac. The lack of response to selection for resistance so far indicates that there is not a high level of resistance genes existing in Australian H. armigera at present. All the evidence from studies on another insect Plutella xylostella overseas confirms the notion that resistance to Bt in H. armigera will occur when the usage of Bt ICPs becomes sufficiently common. This process will be accelerated when both Bt sprays and Bt transgenic crops are used.
Implications
The relatively small number of options for alternative Bt genes for pyramiding in transgenic crops is a matter for concern. The data available from this project indicate the cross resistance between Cry1A ICPs is highly likely and so the only alternatives at present are Cry2A and the new genes which have been identified in a related project funded by RIRDC and the Grains Research & Development Corporation.
RIRDC Project No: CSE-55A
RESEARCHER: Dr Ray Akhurst
ORGANISATION: CSIRO Division of Entomology,
GPO Box 1700, CANBERRA ACT 2601
PHONE: 02 6246 4123 FAX: 02 6246 4173
NOVEL BT TOXINS FOR CONTROLLING INSECT PESTS
Objective
· To isolate insecticidal crystal protein (ICP)-producing Bacillus thuringiensis strains that can be developed as microbial insecticides or insert genes for transgenic plants for the control of a range of insect pests of Australian agriculture.
Background
Some agricultural industries rely heavily on the use of insecticides for controlling insect pests, but this method of control has its attendant problems of environmental contamination, effects on non-target organisms, residues in harvested produce, etc.
An alternative to synthetic insecticides is the use of biological, particularly microbial agents, such as the bacterium Bacillus thuringiensis (Bt) which produces insecticidal crystal proteins. Microbial insecticides based on Bt offer the most promising current option for replacing the use of conventional insecticides. Bt comprises a group of bacteria which carry a wide range of ICPs. The ICPs have a high degree of specificity and are harmless to other animals including humans, making them more acceptable to regulatory authorities.
Some 105 ICP gene sequences have now been reported in strains of Bt. These represent 58 distinct ICP genes which can be divided into major classes and subclasses which reflect differences in host specificity. Until recently, identification of new Bt ICPs has relied on bioassay of samples isolated from the environment. A disadvantage of this technique is the repeated isolation and re-creening of the same ICPs, but the introduction of PCR techniques allows this to be overcome.
Research
New technologies were exploited to isolate novel ICPs from Bt, aimed particularly at the control of beetle pests. Some 5000 isolates of Bt, from both the CSIRO's existing collection, and from environmental samples collected from all mainland states and territories were assessed. Following primary screening for ICP production, secondary screens employing PCR techniques were used to identify ICP genes which are already known. Isolates which did not match known profiles were then assayed against 18 insect pest species in feeding tests. Cloning of the ICP genes from the most toxic isolates was then undertaken as a further step in developing potential new biological insecticides for use against beetle pests.
Outcomes
Sixty eight isolates were found to have novel activity: 13 against Coleoptera (beetles), 43 against Lepidoptera (moths), 9 against Diptera (flies), and 3 against Orthoptera (locusts/crickets). No activity was found against Isoptera (termites).
Two isolates were toxic against the lesser grain borer, and other grain pests were susceptible to other isolates. The susceptibility of the important cotton pest Helicoverpa armigera to 30 isolates raises the prospect of finding effective ICPs that can be used, either as sprays or in transgenic plants, to manage resistance to Bt by this pest which is expected to arise from the use of a single ICP in transgenic cotton.
Implications
The isolation of these novel strains of Bt offers the potential for new bioinsecticides to be developed against a wide range of pests of Australian agriculture. Their ultimate use will contribute to the continued reduction in use of chemical insecticides and protection of export markets. The wealth of useful Bt strains derived from this project could lead to the establishment of a local bioinsecticide production facility. Before this can occur it will be necessary for the various sectors of industry which could benefit, to contribute funds for further research and development. This project has effectively laid the necessary groundwork for further developments.
RIRDC Project No: CSE-57A
RESEARCHER: Dr Ray Akurst
ORGANISATION: CSIRO Division of Entomology, GPO Box 1700, CANBERRA ACT
2601
PHONE: 02 6246 4123 FAX: 02 6248 4173
MINIMISING PESTICIDE USE THROUGH CONTROLLED RELEASE FORMULATIONS OF BACILLUS THURINGIENSIS
Objectives
· To minimise the use of synthetic insecticides and their consequent residues in the dried fruit and grape, horticultural, vegetable and cotton industries through the development of improved formulations of the bacterial insecticide, Bacillus thuringiensis (Bt).
· To develop controlled release formulations of Bt which will extend their periods of effectiveness under field conditions, thus making them more competitive with conventual insecticides.
· To improve the adhesion of Bt formulation to target locations such as leaf surfaces and thus increase their effectiveness against lepidopteran pests.
Background
Many pesticide spray formulations (both chemical and biological) are severely degraded by UV light after application, and rapidly become ineffective against their target pest. This is particularly so in Australia, where UV levels are frequently higher than in other parts of the world. The ability to produce formulations with enhanced UV protection allows lower rates of product to be applied without losing activity, resulting in lower costs and reduced risks of environmental contamination.
This project was directed at improving the UV stability of formulations of the biological insecticide Bacillus thuringiensis (Bt), which is becoming increasingly used on a wide range of Australian crops to control lepidopteran pests such as Helicoverpa armigera in cotton.
Research
The active ingredient in all the research was based on a commercially available source of water-based flowable, "Biobit XLP". Various solid formulations of Bt were developed as wettable powders because of their economic benefits (low bulk and long shelf life). "Celite 545" was chosen as a suitable inert carrier having a large pore diameter, good porosity, and being inexpensive. Various formulations were developed using polymer coatings and other ingredients including adjuvants. Methods were developed to test the degradation of these formulations under UV, in comparison with unprotected Biobit XLP, and efficacy against larvae of lightbrown apple moth was evaluated.
Outcomes
The final formulation developed (BT30) was found to perform to an equivalent standard to the industry leader in encapsulation technology (Encapsid). Both BT30 and Encapsid were significantly more stable under UV than Biobit XLP. BT30 was field trialed on grapevines exposed to natural sunlight, where its efficacy against lightbrown apple moth was excellent. The formulation also maintained good persistence relative to other commercially available products.
Implications
All currently available commercial formulations of BT are produced and formulated overseas (ie imported as formulated product), as the size of the local market does not justify the establishment of a local production facility. Despite the potential benefits which could arise from this project, it is unlikely that new formulations based on this technology will be developed for use in Australia. Attempts are, however, continuing in an attempt to attract a commercial partner to whom the technology can be on-sold.
The industry which will benefit most, is the wine and grape industry. This is not because of the development of an improved formulation of BT, but by the acquisition of a better understanding of the application methods and use rates that are needed to effectively control lightbrown apple moth. Many grape growers have been trying for years to apply BT at effective use rates without contaminating the wine produced from the treated crop. This is now possible to achieve.
RIRDC Project No: DAV-60A
| RESEARCHERS: ORGANISATIONS:
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Dr A. M. Smith Agriculture Victoria Pty Ltd Inst. for Horticultural Dev. Private Bag 15, South Eastern Mail Centre VIC 3176 03 9210 9222 |
Dr B. Hawkett Daratech Pty Ltd Monash University CLAYTON VIC 3168 03 9820 0588 |
BIOLOGICAL CONTROL OF FRUIT PIERCING MOTHS
Objective
· To evaluate two egg parasitoids from PNG, for potential as biocontrol agents of fruit piercing moths, and if successful, to prepare submissions to both AQIS and ANCA for their introduction and release.
Background
Five species of fruit piercing moths are serious pests of tropical and sub-tropical fruit in eastern and northern Australia. The two most important species are pests throughout the year in the tropics and migrate in late spring to southeastern Queensland and northern NSW, where they breed, build up and damage fruit until suppressed by the cooler months. In the tropics, the other three species are destructive at certain times of the year.
Unlike most moth pests that cause damage when larvae, adult fruit piercing moths cause damage at the ripening stage by piercing the rind and withdrawing juice. Natural enemies are believed to maintain the moths at populations below economic damage thresholds in certain countries such as PNG, where at least two such parasitoids are known. In Australia natural enemies are few in abundance and in species diversity and are unable to keep the moths below thresholds.
The two parasitoids from PNG have been successfully tested and introduced to Fiji, Tonga and Western Samoa for control of fruit piercing moths. This project seeks to evaluate these two parasitoids for potential use in Australia.
Research
The two parasitoids Telenomus lucullus and Ooencyrtis papilionis were introduced for evaluation against a range of non-target species of moths (either closely or distantly related to fruit piercing moths), under quarantine conditions.
Outcomes
Not all the non-target moth species initially proposed for testing could be obtained (partly due to the severe drought which occurred in Queensland during the project), and some failed to oviposit; the eggs therefore were not available for exposure to the parasitoids. One of the candidates, O. papilionis, failed to satisfy the stringent host-specificity requirements, since the host recognition of the parasitoid was affected by the plant substrate. This resulted in parasitoids attacking eggs of moths unrelated to the target species when certain plants were present. On other occasions parasitoids wouldn't attack their known host when certain plants were present.
Based on results obtained, the other candidate, Telenomus lucullus appears to be sufficiently specific to be eligible for a recommendation for its release. A list of moth species which do or do not support parasitoid development has been produced.
Implications
This project has identified a possible new biological control agent for fruit piercing moths for introduction into Australia. Telenomus lucullus has satisfactorily demonstrated host specificity in laboratory tests. Approval will now be sought from AQIS and ANCA for its release in Australia but further financial support will be needed to rear parasitoids for release, distribution and field evaluation.
RIRDC Project No: CSE-60A
RESEARCHER: Dr D P A Sands
ORGANISATION: CSIRO Division of Entomology, Private Bag No. 3, INDOOROOPILLY
QLD 4068
PHONE: 07 3214 2803 FAX: 07 3214 2885
PUBLICATION: Workshop on Fruit Piercing Moths - Program and Abstracts, CSIRO Division of Entomology in association with ACIAR, 16-21 January 1995
STRAIN IMPROVEMENT OF THE INSECT BIOCONTROL AGENT METARHIZIUM ANISOPLIAE
Objectives
· To employ molecular techniques to increase our understanding of the genetic basis for pathogenicity and host specificity of the biocontrol fungus Metarhizium.
· To use these techniques to screen/identify more effective strains resulting from genetic transformation of other strains of the fungus.
Background
The entomopathogenic fungus Metarhizium anisopliae infects a wide range of insects and is being developed as a mycoinsecticide. In Australia it is being evaluated against termites and various soil insects such as scarabs and wireworms. It is already commercially available for use in several overseas countries.
An important characteristic of the fungus is its innate genetic variability. Individual strains vary in morphological characteristics, pathogenically, temperature requirements, and biochemical requirements.
A study of the genetic basis for this variation, using molecular techniques, may permit the development of a "super strain" of the fungus which is more pathogenic than existing strains. This project aimed to screen and "fingerprint" large libraries of the fungus in an attempt to understand the phylogeny of the fungus with the view to being able to patent new more effective strains.
Research
Various molecular and biochemical techniques were used to study the genetics of Metarhizium anisopliae, with a view to identifying markers which could be used in population studies. Large numbers of isolates of the fungus were studied.
Outcomes
This project was not able to identify the genetic basis of pathogenicity of the fungus, or to improve the pathogenicity of isolates/genetic crosses, but has resulted in: a proposed change in the taxonomy of the genus Metarhizium; improved "finger printing" of isolates of the fungus using two complementary molecular techniques; and a better understanding of the host specialisation in Metarhizium. Strains of the fungus can now be identified which are pathogenic to crickets, solder fly, redheaded pasture cockchafer, peanut scarabs, termites, and root aphids.
Implications
Although new "super strains" cannot be produced using current technologies, it is likely that these will be produced satisfactorily in the future.
RIRDC Project No: CSE-61A
RESEARCHER: Dr Richard Milner
ORGANISATION: CSIRO Division of Entomology, GPO Box 1700, CANBERRA ACT
2601
PHONE: 02 6246 4169 FAX: 02 6246 4042
DEVELOPING PHEROMONE BASED CONTROL SYSTEMS FOR PEST LEPIDOPTERA
Objectives
· To develop a field version of electroantennogram (EAG) equipment to detect pheromone concentrations using the antenna of a live insect.
· To build a wind tunnel which will allow release rates of pheromone dispensers to be measured in the laboratory over a range of temperatures and air velocities.
· To develop an actograph which will allow the flight activity of female moths to be measured in the laboratory.
Background
Improved monitoring of insect pest populations provides the basis for introducing refined control strategies and thereby reduce dependence on the use of synthetic chemical insecticides. One such activity is the use of synthetic sex pheromones in cropping situations to better monitor insect populations, and in some cases to disrupt mating behaviour. Pheromone technology, especially in the area of mating disruption, is under continuous development but the tools for evaluating its performance are often inadequate. This project seeks to design improved instrumentation of three key areas so that better and more effective monitoring of pest populations can be undertaken.
Research
Electroantennogram (EAG) measurements were conducted in orchards using both Light Brown Apple moths and Codling moths. The equipment used was capable of detecting pheromone pulses emanating from pheromone dispensers, and was comparable in performance to that developed for similar research in NZ and Germany.
The characteristics of pheromone dispensers (currently on sale commercially for controlling Oriental fruit moth), and of a new range of dispensers being evaluated against Codling moth, were tested in a wind tunnel. The flight activity of females of three species (Codling moth, Light Brown Apple moth, and Oriental Fruit moth) were measured over a range of ages. The effects of exposing the latter two to synthetic pheromone was also investigated.
Outcomes
In the EAG studies, the instrument which was developed performed well but it was found that strong responses to environment odours prevented the measurement of absolute concentrations of pheromone for the two species of interest. The release properties of the pheromone dispensers were characterised over a wide range of conditions with a level of precision which was previously unattainable. A number of important formally unidentified conditions were established for accurately measuring dispenser performance. The flight activity patterns of female moths were found to be species dependent, and these did not change when the air was permeated with pheromone.
Implications
These results of these studies, while not having any further immediate industry application, continue to improve our understanding of pheromones and the role they may usefully play in improved insect control strategies which rely less on the use of insecticides.
RIRDC Project No: CSE-63A
| RESEARCHERS: ORGANISATIONS: PHONE: |
Dr E R Rumbo CSIRO Division of Entomology Private Bag No. 3 INDOOROOPILLY QLD 4068 07 3214 2811 |
Dr T E Bellas CSIRO Division of Entomology GPO Box 1700 CANBERRA ACT 2601 02 6264 4093 |
DEVELOPING CO-FORMULATIONS OF HERBICIDES TO PREVENT RESISTANCE
Objectives
· To improve the adoption strategies aimed at the prevention of herbicide resistance by developing co-formulations of triallate and trifluranlin which can be delivered in a convenient single pack.
· To evaluate the agronomic performance of these co-formulations against industry standards.
· To ensure that company sales and technical staff are adequately informed of the advantages of these formulations.
Background
The development of herbicide resistance posed a major threat to various cropping enterprises in Australia, with resistance in annual ryegrass alone costing around $57 million per annum. Prevention of the onset of resistance is vital and involves, amongst other strategies, the use of mixes of herbicides from various chemical groups.
The adoption of this strategy by farmers has been limited, due mainly to the inconvenience of tank-mixes or problems with tank-mix antagonism. In addition this tank-mix has been regarded as having problems with antagonism and volatilisdation. Herbicide manufacturers tend not to develop co-formulations for two main reasons - in their present form many herbicides are incompatible and so cannot be readily combined, and, the markets are too small to warrant the research expense required.
If re-formulation strategies can be developed to permit the blending of active constituents without the need for using flammable solvents, then it may be possible to produce co-formulations of Group D herbicides (triallate and trifluralin) which can be delivered in the same pack. This would remove some of the impediments to a wider uptake of this desirable weed control strategy.
Research
Enhanced delivery systems for triallate/trifluralin co-formulations having high loading levels of active constituents were developed in the laboratory. Three major delivery systems (=formulation types) viz. wettable powders (WP), emulsions in water (EW), and emulisifiable concentrates (EC) were examined. Initially, these were evaluated in the laboratory for their various chemical and biological attributes, and the most promising were further evaluated in field trials over two seasons (various rates of application were compared with the "industry standards").
Outcomes
In the first year's field testing, two emulsion in water (EW) co-formulations provided biological efficacy against wild oats and annual ryegrass equivalent to that of the tank-mix. The extra cost of manufacture of this formulation however, preluded any further attempt to commercialise it. In the second year, an emulsifiable concentrate (EC) significantly outperformed the standard treatment. This formulation (EC6) has reduced volatilisation (a clear benefit if used in a tropical environment), is expensive to manufacture and package, and contains a low flammability solvent.
Implications
Although the aims of this project have clearly been accomplished, there is little likelihood that the technology developed will be commercialised. The benefits of the new co-formulation are obvious to the commercial collaborator, Nufarm Limited, the Australian manufacturer of trifluralin. Monsanto, the sole manufacturer of the second component of the co-formulation (triallate) was, until recently, interested in the proposed product but following market research, has decided that to proceed would be at the expense of other more profitable products in its current range. Without the active support of Monsanto, there is little opportunity for successful commercialisation.
RIRDC Project No: DAR-28A
RESEARCHER: Dr Brian Hawkett
ORGANISATION: Daratech Pty Ltd, 3rd Floor, 493 St Kilda Road MELBOURNE
VIC 3000
PHONE: 03 9820 0588 FAX: 03 9820 0480
VIRTUAL PLANTS: A REVOLUTIONARY APPROACH TO CROP EXPERIMENTATION
Objective
· To augment a new, generic, computer model of modular growth of plants to enable pest and disease management options to be stimulated, initially by measuring responses of stylo to attack by Heliothis and anthracnose and building response-simulation routines into the model.
Background
There has been little work at the intermediate level of plants as populations of modules, and almost no work at this level investigating the effects of diseases and pests. Now, there is affordable hardware and the software is being developed to fill this gap.
The development of this type of computer modelling has the potential to improve research efficiency in many areas of cropping, grazing, pruning, and biological control of weeds by allowing "virtual experiments"(simulatating damage responses in host plants to attack by pests or pathogens) to be undertaken in greater numbers at little cost, leading to more focussed design of actual field experiments.
Research
Using the tropical pasture species "stylo" (Stylosanthes scabra) as the host plant, the pest Heliothis and the fungal pathogen Colletotrichum, software was developed to reflect plant development in the presence of these damaging agents. The study was designed to explore the effects of both agents on each other and on the morphogenesis of a shared host. The principal aim was to investigate how necrosis by the fungus and removal of apical meristems by larvae of Heliothis affected morphogenesis of the host.
Experiments were designed to investigate plant responses to various damage scenarios. Observations of plant development were analysed statistically and converted into rules of morphogenesis. These were then expressed to create visual representations of sequential plant growth. The research was undertaken in close collaboration with the world expert in this field, Prof. Prusinkiewicz, of the University of Calgary, Canada.
Outcomes
Insect grazing alone caused minimal damage in whole-plant development rate but did affect main stem internode lengths, and leaf size on branches. Simulated grazing (using scissors) to remove apical meristems had a greater effect on morphogenesis than removal of leaf tissue only. A shift in apical dominance and compensatory growth by the top three remaining branches was noted as a result of apex removal, resulting in plants which were shorter and more "bushy".
Similarly, anthracnose infection which stopped apical growth caused greater branch development lower down the plant than on control plants, but the effect was less than when apical meristems had been removed with scissors. Infection also reduced internode growth, stunting the most recently emerged internode regardless of position or the age of the plant.
Oviposition and larval grazing by Heliothis were reduced in the presence of anthracnose disease, but larval grazing did not affect disease, but larval grazing did not affect disease establishment at three inoculum concentrations.
Implications
The major objective of using the stylo study to provide practical experience and feedback when extending and further developing software for use in modelling the structural development of plants has been highly successful.
Copies of the software, and the user manual, for 3D digitising plant architecture and conversion of records into lengths, angles and "stick" images of plants have been made available to the research community via the "Virtual Plants" site on the world wide web at: http://www.ctpm.uq.edu.au/Programs/IPI/ipivp.html
The virtual laboratory software for simulating structural growth of plants has also been augmented by the Canadian collaborators at the University of Calgary, and is available for downloading free of charge, from their site at:http://www.cpsc.ucalgary.ca/projects/bmv/vlab/index.html
RIRDC Project No: CSE-58A
RESEARCHER: Dr Peter Room
ORGANISATION: CSIRO Div. of Entomology, Private Bag No. 3, INDOOROOPILLY
QLD 4068
PHONE: 07 3214 2700 FAX: 07 3214 2885
MOLECULAR DIAGNOSIS OF ROOT-KNOT NEMATODE (MELOIDOGYNE SPP)
Objective
· To improve a previously developed diagnostic test by increasing its reliability, predicting host range and detecting root-knot nematode, Meloidogyne, in soil and plant roots.
Background
Root-knot nematode is a multi-industry problem affecting nearly every crop species grown, and causing an estimated yield loss in Australia of more than $200 million each year. Nematicides control all species and races of root-knot nematodes but many non-chemical control methods, such as crop rotation, resistant cultivars and biological control, are species-specific. To use these strategies for root-knot nematodes, it is necessary to detect and identify nematodes in root and soil samples.
Current identification methods using morphological features and a standard host range test are insensitive, inaccurate, and time-consuming. The development of improved molecular diagnostic techniques will overcome these deficiencies.
Research
Work in this project built on achievements in a previous project by optimising the PCR-based mitochondrial DNA (mtDNA) diagnostic test already developed, and by exploiting the possibilities of improving the test to predict host range and to detect nematodes in soil samples and plant roots. Optimisation of the test involved devising primers which are positioned so that amplification is reliable and optimising all amplification conditions and reagent concentrations. Several additional plant genotypes were tested for their ability to distinguish mtDNA groups. Further genetic studies, involving the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene and RAPD assays using long primers, searched for markers related to host range.
Outcomes
The diagnostic test based on mtDNA groupings was refined to allow reliable amplification in 95% of cases and can also detect components of mixtures if present as at least 50% of the total DNA. No plant genotypes were found which elicited reactions which were related to mtDNA groupings. Furthermore, although nematode reactions on certain host were variable, differences between populations were not sufficient to act as easily recognisable race markers. The ITS region has a very complex structure, so is not likely to be useful as a molecular marker. However, two RAPD loci may have potential as specific markers for M. incognita.
A diagnostic test is now available to identify any life stage of Meliodogyne populations. Although the test will not predict host range of all Australian populations, it is an extremely important research tool eg. for distinguishing populations which exist in a cropping system in a region, and thus allowing screening for resistance specifically to them. It is now in use by QDPI for management of root-knot nematodes on tobacco, vegetables, and sugarcane.
RIRDC Project No: DAQ-151A
RESEARCHER: Dr Jim Stanton
ORGANISATION: Qld Department of Primary Industries, PO Box 46, BRISBANE
QLD 4001
PHONE: 07 3877 9574 FAX: 07 3877 9574 NATIONAL EVALUATION OF
DIAGNOSTIC CAPABILITIES FOR AUSTRALIAN PLANT INDUSTRIES
Objectives
To provide Australian cropping industries with a diagnostic capability of world standard by: · conducting a skills gap analysis of the current diagnostic capability in Australia; · developing a communication network between existing diagnostic laboratories; · critically evaluating new techniques for their introduction into Australian laboratories; and · identifying future research directions for the improvement of delivery of diagnostic services.
Background
Australian agriculture relies heavily on the use of agrochemicals for control of pests, weeds and diseases, at an annual cost of more than $800 million. These chemicals are often used needlessly or inappropriately, resulting in increased costs to growers, a likely increase in chemical resistance, adverse environmental effects, and threats to trade. The key to judicious use of chemicals is rapid and accurate diagnosis of the presence of pests or diseases to establish the need for such treatments.
In Australia expertise in pest and disease diagnostics is diminishing, while there is an increased demand for these services by industry. A skills gap analysis is required of current national diagnostic capabilities. This will facilities the development of a coordinated national approach to the most efficient use of existing expertise in Australian diagnostic laboratories.
Research
Australia's plant pest and disease diagnostic laboratories were identified and their current capabilities determined by means of a questionnaire survey. This was followed by a national workshop at which a wide range of issues relating to diagnostics were discussed. The need for a national diagnostics communication network was canvassed, and a desktop study of diagnostic technologies was undertaken, and reviewed by workshop participants.
Outcomes
Our national diagnostic capabilities (or lack of) have been clearly established, and a range of deficiencies identified. At the workshop, the importance of herbarium reference collections as an aid in diagnostics, particularly for quarantine purposes, was highlighted. Unfortunately these collections are not being adequately supported.
Training programs are needed to offset the loss in the diagnostic skills base, and there is a need to upgrade computing, communication and business skills of current diagnosticians. A new communications network for diagnosticians has been established as has a database on the world wide web, which contains information about Australian plant disease diagnostic services (eg: numbers of staff, services offered, contact details etc.). This is available at: http://www.vicnet.netau/~primary/av/regions/ihd/industry/diagdata.html
A desktop study of new technologies has resulted in the development of a database of more than 400 references on new technologies, and applications in the field of plant pathology.
Implications
Unless the gradual demise of our national diagnostic capability is arrested, many agricultural industries will be at risk, particularly those which are export oriented. Deficiencies in training have been identified, and future research directions prioritised. Adoption of new technologies not currently being used will provide an opportunity for improving the quality and timeliness of diagnostic services.
RIRDC Project No: DAV-107A
RESEARCHER: Ms Jane Moran
ORGANISATION: Agriculture Victoria Institute for Horticultural Development,
Private Bag 15, SOUTH EASTERN MAIL CENTRE VIC 3176 PHONE: 03 9210 9222
FAX: 03 9800 3521
AUSTRALIAN PHYTOPLASMA DISEASES: RAPID IDENTIFICATION TECHNIQUES AND PREDICTION MODELS
Objective
· To develop rapid identification techniques for the detection of phytoplasmas thereby permitting the validation of economic prediction models for the control of phytoplasma diseases.
Background
Phytoplasmas (formerly called MLOs) are associated with more than 200 diseases, many of which occur in horticultural crops. In Australia, phytoplasmas of economic importance include tomato big bud, potato purple wilt, grapevine yellows, and strawberry little leaf. In all these diseases the phytoplasmas are phloem restricted and can not be cultured in vitro.
This has resulted in great difficulty in establishing rapid and accurate diagnostic techniques for phytoplasmas, both for plants and insect vectors, resulting in epidemiology studies being long term and labour intensive. Recent advances in technology such as PCR (polymerase chain reaction) offer opportunities to develop sensitive and rapid techniques for the detection and characterisation of phytoplasmas, leading to cost-effective control strategies such as those based on predictive models.
Major outbreaks of phytoplasma diseases occur unpredictably, and in many years, control measures are not warranted. The use of prediction models, verified through the use of reliable detection techniques would ensure that growers employ control measures only when the disease incidence is above the economic damage threshold. These models would have potential for a wide range of important crops such as tomatoes, potatoes, grapes and strawberries.
Research
The economically important disease Tomato Big Bud (TBB), transmitted by the leafhopper vector Orosius argentatus, was selected for use in this study. The phytoplasma was maintained in two hosts (periwinkle and tomato) in a glasshouse, while the leafhopper vector was also maintained on three hosts (celery, mallow, and broad bean) in a separate glasshouse in the absence of Tomato Big Bud.
Leafhoppers were collected from two field sites at Rochester (from lucerne) and Ovens (from white clover) in northern Victoria, and used to establish a working colony. The parent population was reared on mallow, grown in cages in the glasshouse under controlled conditions. Subsequent populations were maintained on celery plants under similar conditions. Subsequent populations were maintained on celery plants under similar conditions. PCR was used to test for the presence of phytoplasmas in the colonies.
Healthy leafhoppers were fed on TBB infested plants to acquire the phytoplasma, and then transferred to healthy celery plans before transmission tests were undertaken on a range of indicator plants. Plants and leafhoppers were tested for the presence of TBB. Standard techniques were used for extracting DNA from both plants and leafhoppers and the samples were tested using PCR.
Outcomes
A primer specific for phytoplasmas was successfully used to detect TBB in both the leafhopper and infected plants. The technique developed cannot, however, be used to detect phytoplasmas in leafhoppers which have been stored in 90% ethanol at room temperature for longer than one month (ie. is unsuitable for testing stored material such as in museum collections).
Implications
The protocols developed for detecting TBB in leafhoppers and various host plants has been successfully adapted to detect other phytoplasmas in 43 different plant species from 17 families. The protocol is now being successfully used in Agriculture Victoria's commercial diagnostic service.
RIRDC Project No: DAV-93A
RESEARCHER: Jane Moran
ORGANISATION: Agriculture Victoria Institute for Hort. Development, Private
Bag 15, South Eastern Mail Centre, VIC 3176
PHONE: 03 9210 9222 FAX: 03 9800 3521
ASSESSMENT OF SYSTEMIC INDUCED RESISTANCE IN PLANTS AS A COMPONENT OF INTEGRATED PEST AND DISEASE MANAGEMENT
Objective
· To assess the biological spectrum, mechanisms and effectiveness of systemic induced resistance in legumes as brought about by biological and chemical means.
Background
Systemic induced resistance (SIR) is a process whereby a plant becomes resistant to a pathogen after earlier exposure to a pathogen, an attenuated form of a pathogen, or a chemical that is not itself a pesticide.
The continued development and use of traditional pesticides is under severe pressure internationally and in Australia for economic, environmental, legal and political reasons. The plant protection industry is undergoing major readjustment. As part of that readjustment, integrated pest and disease management will become a major goal. One strategy in achieving the goal will be the manipulation of natural defence mechanisms in plants, including the use of systemic induced resistance wherever possible.
No commercial examples of systemic induced resistance currently exist, but this study, in collaboration with the multinational agrochemical company Ciba Geigy, is aimed at elucidating some of the mechanisms of the process concerned using Phaseolus beans and certain foliar fungal diseases as a model system.
Research
Under either controlled environment or field conditions, seedling plants of Phaseolus vulgaris were challenged with inoculum of various fungal pathogens, or with a chemical inducing agent (CGA 41396). This was done by inoculating the first seedling leaf on each plant.
After appropriate intervals the second leaves or later developing plant parts received inocula of the pathogens concerned. Disease development was assessed on these leaves or plant parts using relevant disease keys (indicating % of tissue diseased), routinely at weekly intervals. Assessments on treated and control plants were contrasted and analysed for variance and significance of differences.
Trials were undertaken against rust and anthracnose diseases, and against root and stem base infections in Phaseolus. Activities of the enzymes glucanase and chitinase and concentrations of salicylic acid were measured in different parts of treated plants.
Outcomes
Following pre-treatment of the first leaf with either a pathogen or the chemical inducing agent, the numbers of resultant disease lesions were significantly lower for pre-treated plants than for the controls. The chemical inducing agent CGA 41396 was as effective or more so than the fungal pathogens in protecting Phaseolus plants against the pathogens used. These results were consistently obtained with fungal foliar diseases, but systemic induced resistance was not effective in the case of soilborne diseases.
Implications
The results obtained confirm the feasibility of using this approach to disease control, but considerable research is still required to fully elucidate the mechanisms involved.
Since this project commenced, Ciba Geigy have developed a new more effective compound than was used by these researchers (CGA 245704). Registration for commercial use of the compound is currently being sought. Systemic induced resistance (or at least one example of it) will become commercial reality within a few years, and it will both reduce the dependence on the use of conventional fungicides, and enhance the adoption of integrated pest and disease management strategies.
RIRDC Project No: US-21A
RESEARCHER: Prof. B.J. Deverall,
ORGANISATION: Department of Crop Sciences, University of Sydney, NSW 2006
PHONE: 02 9351 2531 FAX: 02 9351 4172
EMAIL: bdeveral@extro.ucc.su.oz.au
BIOLOGICAL CONTROL OF MOUSE PLAGUES
Objectives
· To determine through a restricted field release on the Darling Downs in south eastern Queensland and in the Mallee wheatlands of north western Victoria, whether biological control of mouse plagues is effective and economic using a liver nematode, Capillaria hepatica.
· To monitor changes in the occurrence of murine viruses during fluctuations in mouse populations on the Darling Downs.
Background
Mouse plagues occur nationally, causing high economic losses to grain growers and major social problems. In 1993 economic losses in southern Australia were estimated to be around $65 million, and > $5 million in south eastern Queensland. Extensive use of chemicals, as occurred in 1993 and 1994, causes environmental problems and puts at risk important export markets.
Clearly, a biological method for controlling mouse plagues may provide an environmentally and potentially economically attractive alternative to the use of chemicals. The evaluation of potential biocontrol agents against mice is therefore warranted.
Research
In this project, restricted field releases of a nematode liver parasite, Capillaria hepatica, were made in 1992 and 1993 on the Darling Downs in south eastern Queensland, and in late 1993 in the Mallee wheatlands of north western Victoria. The population dynamics of the mice following release of the parasite were monitored in both regions and the presence and distribution of the parasite was determined. The dynamics of other diseases of mice was examined with the research on C. hepatica. This study was concentrated on viruses, other helminth parasites and a bacterium Streptobacillus moniliformis.
Outcomes
Although effective baiting methods have been developed and the nematode parasite can be effectively distributed in the field, the level of infections which occur in mice are not sufficient to control mouse plagues. A level of mouse control can be achieved when populations are high, but low mouse populations mitigate against effective dispersal of the parasite from one mouse to another. No major new biocontrol agents were identified in studies on other diseases of mice on the Darling Downs.
Implications
This study, which was also funded by GRDC, generated large amounts of data and attracted the collaboration of scientists from other countries. It is clear that the nematode parasite used in this study is effective against individual mice, but does not appear to have the potential to be used effectively to prevent the occurrence of plagues. Current long-term studies focussed on immunocontraception using a genetically engineered virus are more likely to rely to provide a solution to this problem.
RIRDC Project No: CSW-27A
RESEARCHER: Dr GR Singleton
ORGANISATION: CSIRO Division of Wildlife and Ecology, PO Box 84 LYNEHAM
ACT 2602
PHONE: 02 6242 1600 FAX: 02 6241 3343
NEMATODE CONTROL WITH ORGANIC AMENDMENTS AND ROTATION CROPS
Objectives
· To screen crops for resistance to Australian populations of root-knot nematode.
· To evaluate nematode-resistant rotation crops in the field and examine their potential for use in nematode management.
· To devise an assay system to quantify the suppressiveness of soils to root-knot nematodes and determine whether the natural biological suppression that is induced by organic manuring can be predicted by measuring the microbial status of soil.
Background
Root-knot nematodes (Meloidogyne spp.) are Australia's most important nematode pest. They have a debilitating effect on many perennial crops, and are one of the major factors limiting production in many intensively managed cropping situations.
Crop rotation is one of a limited range of nematode control options that are currently being investigated as alternatives to the use of chemicals. It has never, however, been universally used against root-knot nematodes because they have an extremely wide host range (more than 2000 plant species), resistance tends to be species-specific, and species of Meloidogyne have been difficult to identify reliably.
Recent developments in molecular identification technologies have removed this impediment and there is now renewed interest in the possible incorporation of crop rotations into integrated management systems for root-knot nematodes.
Research
Approximately 240 accessions of 73 crops were screened for resistance to Meloidogyne javanica, M. incognita (races 1 and 2), M. arenaria (race 2), and M. hapla - the four most common root-knot nematode species in Australia. In initial screening the level of reproduction was measured by counting eggs produced after about 8 weeks. The most resistant material was then re-examined in more comprehensive tests. A range of organically amended and non-amended soils from home gardens, organic farms and field trial sites were bioassayed for suppressiveness to root-knot nematode, while their biological status was also determined by measuring % organic carbon, microbial biomass and microbial activity.
Outcomes
Almost half the crops tested contained accessions that were resistant to at least one species of Meloidogyne. Accessions of most crops exhibited a similar level of resistance to all species of Meloidogyne, but there were important exceptions. For example, Capsicum was only susceptible to M. incognita. In some crops (eg. Setaria, Avena, Sorghum, and Zea) some accessions were resistant and others susceptible, while in other crops, all accessions were either resistant (eg. Arachis, Brachiaria, Chloris, and Panicum) or susceptible (eg. Phaseolus, Vicia, and Vigna). Some soils were found to be suppressive and there was a significant relationship between the microbial activity of soil and suppressiveness.
Implications
Many of the resistances identified can be used in crop rotations to minimise the damaging effects of root-knot nematodes. Results of field experiments clearly show, for example, that a susceptible crop such as zucchini is not heavily galled (damaged) when it is planted in rotation after relatively resistant crops such as forage sorghum, pinto peanut and watermelon, but heavy losses occur if it follows susceptible crops such as maize or sweetcorn.
The results from studies on suppressiveness suggest that it might eventually be possible to measure specific soil parameters and determine whether a soil is biologically active enough to provide some control of nematodes.
RIRDC Project No: DAQ-152A
RESEARCHER: Dr. G.R. Stirling,
ORGANISATION: Department of Primary Industries, Plant Protection Unit,
Meiers Road, INDOOROOPILLY QLD 4068
PHONE: 07 3896 9392 FAX: 07 3896 9533
Last updated: 25 October1997
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