There is a need to develop technologies that can be used to rapidly detect and quantify pest infestations in bulk grain to assist in the management of these biosecurity threats. This project identified and characterised pheromone receptors in the genome of Tribolium castaneum, common insect pest of stored grain.

Research outcomes:

The experimentally derived information regarding the proteins involved in the perception of the T. castaneum produced volatile DMD, will aid in the development of a biosensor platform for the detection of this stored grain insect. The key information uncovered during the course of this project included:

• Adult and larvae T. castaneum respond to infested flour more than clean flour.
• Both adults and larva respond behaviourally to DMD with female adults displaying the highest sensitivity to the compound.
• The antennae of T. castaneum responded to four beetle odours, including the aggregation pheromones for Rhyzopertha dominica and itself, but only its own pheromone caused a significant behavioural response.
• Male beetles express at least three receptors at higher levels than females, and females express at least one receptor more highly than males. These are candidate pheromone receptors.
• Insect Sf9 cells are not suitable for the expression and characterisation of T. castaneum olfactory receptors using calcium influx assays.
• The OBPs we expressed and purified are capable of solubilising (which indicates direct binding to) DMD, and therefore also make good candidates for use in a biosensor platform.

Research implications:

• The implication of finding putative pheromone receptors of the stored grain pest, T. castaneum, means we have candidates for the biorecognition component of a biosensor device.
• The development of a grain pest biosensor would allow greater control and efficiency for grain pest management applications. This would facilitate the maintenance of access to export markets and minimise the level of phosphine-resistance in stored grain pests, which is a key threat to market access.
• Capabilities developed through the course of this project can potentially be applied to other stored grain pests, and indeed, to other applications requiring monitoring of volatiles.

Acknowledgements:

• Sylwek Chyb
• Trécé Inc. (Oklahoma, USA)
• Professor Cobb, University of Manchester
• Dr Tamara Cooper (SARDI Entomology) for her technical expertise and help in the expression and purification of the OBPs
• CSIRO staff and students - Cécile Faucher; Lijun Cai; Stephen Trowell; Amalia Berna; Michelle Michie; Thomas Wallenius; James Darby; Wolf Wanjura

Purpose for travel:

Attend Personal Digital Assistant (PDA) workshop in Perth to contribute to the workshop outcomes, develop networks and discussed potential future project collaborations.  In addition I presented examples of PDA's used for agricultural research within DPI&F and provide input and technical advice to advance the use of PDAs in the CRC.

Increasing applications of phosphine to stored grain in silos that leak, or grain stored under the wrong conditions, has caused problems with insect pests building up resistance. Proof is needed to show whether phosphine fumigation of cool grain is effective in controlling resistant biotypes of insect pests of stored grain.

Research outcomes:

This project assessed the efficacy of phosphine fumigation against resistant insects in cool grain, i.e. aerated grain or grain that has been harvested and stored in the cooler months of the year, and developed recommendations for Australia’s grain storage industry. Grain temperatures of
20°C or less are considered cool. The project will contribute to keeping Australia’s grain export industry free from insect strains resistant to phosphine. Increasing applications of phosphine to stored grain in silos that leak, or grain stored under the wrong conditions, has caused problems with insect pests building up resistance. Proof is needed to show whether phosphine fumigation of cool grain is effective in controlling resistant biotypes of insect pests of stored grain.

The project has:

• provided reports describing new data on phosphine efficacy at low temperature against resistant grain insects
• provided reports describing new data on phosphine sorption by grain
• provided reports describing new data on phosphine fumigation of cool grain in sealed farm silos, and
• made recommendations to farmers and others within the grain industry.

Recommendations on phosphine fumigation of cool grain have been reported to representatives of the grain industry and national extension network at annual meetings of National Working Party on Grain Protection (NWPGP). Results, recommendations and technology transfer have been provided to the Australian grain industry via the NWPGP and industry forums and publications. CRC partners, bulk grain storage operators and handlers have been informed of the findings.

Research implications

Successful fumigation of resistant insects requires sufficient phosphine concentrations for long enough to control all life stages of the insects. Lower temperatures maintain grain quality and reduce insect population growth, but phosphine is generally less effective at lower temperatures.

The relative importance of phosphine resistant strains of key pests changes with temperature. The most resistant Australian strains of two pests are known to respond similarly to phosphine but the project showed that one species became much harder to control in cool grain.

Sorption will be the major cause of loss of phosphine in a wellsealed silo. Rate of sorption was lower at lower temperature, meaning that higher concentrations will be achieved for longer. Older grain tended to be less sorptive, so delaying fumigation may result in higher concentrations for longer. Sorghum was more sorptive than wheat so the margin for error is smaller for this grain.

In farm silos, phosphine gas was liberated from the aluminium phosphide formulations used despite the low grain and ambient temperatures (e.g. 10°C).

The results for the silo trials varied but three general observations were made. Lower concentrations tended to be measured deeper in grain mass. Lower concentrations tended to be measured on the northern side. Concentrations measured higher in the grain mass tended to peak earlier.

The silo trials showed that control of resistant insect populations is possible subject to good gas-tightness and adequate exposure periods. Exposure to cool temperature alone was not the cause of insect mortality.

Growers and others planning to fumigate cool grain in sealable silos should aim for the current silo pressure test standard of a three minute halving time for a full silo or a five minute halving time for a partially full silo.

The use of forced or passive recirculation methods (e.g. the thermosiphon) should be investigated to promote rapid and even distribution of phosphine from the headspace throughout the grain bulk.

Acknowledgements

The project team is grateful for the cooperation of the following growers and their families: Mr Rodney Petersen (Killarney, Qld) and Mr Raymond Fulwood (Meenaar, WA).

This project improved the preparedness of Australia's grain industry for incursions of Emergency Plant Pests (EPPs) by developing a national surveillance plan to support market access and provide contingency plans for threats to Australia's grains industry.

Research outcomes:

• Twenty two contingency plans for key high and medium priority pest threats to the Australian grains industry were prepared. These plans provide information on pest life cycles, potential distribution, survival strategies and methods for surveillance and sampling to assist with biosecurity preparedness.
• Audit of grain pest specific reference material held electronically by PHA was undertaken.
• Biosecurity awareness information was provided to researchers, growers, grains bulk handlers and agribusiness in the form of media articles and seminars.
• Development of surveillance plans for Russian wheat aphid, Hessian fly and Sunn pest to assist capture of data for both early detection of new pests and market access requirements.

Research implications:

The development or update of contingency plans for key pest threats and surveillance plans for Russian wheat aphid, Hessian fly and Sunn pest, together with the delivery of biosecurity messages, form an important part of biosecurity preparedness and prevention activities for the grains industry.

The development of contingency plans will provide information that will form the basis of response plans to pest incursions. The provision of information within the contingency plans will assist with more rapid eradication, containment or management mechanisms being put in place, helping both deliverers and beneficiaries of the emergency response.

Provision of awareness training and information is an important part of industry preparedness, assisting to increase the understanding of the importance of biosecurity and the response mechanisms Australia puts in place in the event of an incursion.

The surveillance plans for Russian wheat aphid, Hessian fly and Sunn pest provides a framework for a coordinated national approach to collection and capture of data for both early detection of new pests and market access requirements.

The surveillance plans assessed the probability of detection of each of these pests using routine crop monitoring. This framework has implications for all stakeholders in the grains supply chain that will be impacted by pests of market access concern or potential pest incursions.

Acknowledgements:

PHA wishes to acknowledge the CRC for National Plant Biosecurity (CRCNPB) and the Grains Research and Development Corporation (GRDC) for supporting this project.

PHA also acknowledges all experts who contributed to completion of contingency plans.

Outcome 

Post-harvest grain biosecurity.

Goal

Maximise the value, integrity, and competitive advantage of Australia’s post-harvest supply chain.

Indicators of success

Economic:

Strategy for extending the useful life of phosphine to support market access outcomes for Australian grains.

Science:

New knowledge underpinning strategies to manage phosphine resistance is accepted by peers through publication.

Policy:

Standardised detection and measurement of resistance to phosphine is accepted by end-users.

Capacity/Collaboration:

Improved phosphine resistance management practice both on-farm and in all sectors of the post-harvest grains supply chain.

Impact/Adoption:

New tools to optimise chemical applications in grain storage are adopted by end users.