Integrating effective phosphine fumigation practices into grain storage systems in China, Vietnam and Australia

• Zhengzhou Grain College, China
• State Administration of Grain, China
• Guangdong Institute of Cereal Science Research, China
• Postharvest Technology Institute, Vietnam
• Chengdu Grain Storage Research Institute, China
• Ministry of Agriculture and Rural Development, Vietnam

Australia (about 25-30 million tonnes), China (495 million tonnes ) and Vietnam (30 million tonnes) produce significant grain harvests each year, including rice, wheat, maize and other grains. Each country fumigates about 80 per cent of this grain with phosphine. Due to the combined advantages of low cost, ease of use and acceptance as a residue-free treatment, this fumigant will remain the central component of insect pest management for the foreseeable future in Australia and throughout Asia. However, scientists in an earlier ACIAR project identified that resistance in target pests threatens the continued viability of this fumigant. It also became apparent that several other factors, in addition to resistance, were contributing to control failures with phosphine.
To ensure the continued viability of phosphine technical innovations are needed to enhance the efficacy of phosphine, also management strategies to control several psocid species (which have developed as a major problem in stored grain in China). Psocids have also emerged as a major problem in Australia, and initial work here has shown that resistance to phosphine is an important factor, but ecological aspects may also be important.

This project aimed to formulate and verify national fumigation standards for China, Vietnam and Australia, to improve fumigation practices in China and Vietnam through training programs, to investigate potential innovations to enhance the efficacy of phosphine fumigation, and to determine the key factors preventing control of psocids with phosphine.

The scientists formulated national fumigation standards for China, Vietnam and Australia. In China and Vietnam, in consultation with local grain authorities, they proposed national standards based on results of research in ACIAR Project PHT/1994/015 and evaluated these standards against resistant strains in the laboratory and in a representative range of farm and central storages. In Australia the scientists proposed national standards based on results of PHT/1994/015 as well as research supported by GRDC and QDPI, and submitted these proposals to National Registration Authority after approval of the National Working Party on Grain Protection.
Improvements to fumigation practice in China and Vietnam were encouraged through training programs. Workplace health and safety was a priority. Chinese and Vietnamese personnel then conducted training workshops for their respective regional storage staff. Both countries used computer-learning tools (developed in earlier ACIAR-funded work) to underscore integration of correct fumigation techniques for effective pest management. In Australia GRDC supported projects, led by Dr Graham White (QDPI), aimed at improving the safe use of phosphine nationally and improving grain storage management practices on-farm.
The scientists also investigated potential innovations to enhance the efficacy of phosphine fumigation, such as the potential synergistic effect of elevated levels of carbon dioxide on phosphine toxicity using flow-through apparatus (China). In Australia they investigated the influence of fluctuating concentrations of phosphine on efficacy, and the effect of fumigation temperature on efficacy against resistant insects.
To determine the key factors preventing effective control of psocids with phosphine, the scientists used a flow-through technique to investigate resistance levels. They undertook laboratory-based life history studies and field studies of the ecology of major species in relation to integrated pest management strategies. They characterised resistance to phosphine in major pest species. From their studies they formulated fumigation protocols and integrated pest management strategies.

National fumigation standards for various storage types, aimed at controlling strongly resistant insects and including best management practice, were established in each participating country. The standards were based on broad surveys of insect populations to identify resistant phenotypes, laboratory characterisation of resistance levels and extensive field trials of proposed protocols.
National standards for modern grain storages and bag-stack fumigations were established and published by Chinese State Administration of Grain. In Australia, research under-pinned an extensive review of phosphine registration. New registration labels for cylinder-based formulations have already been published and label changes for solid formulation aluminium phosphide are currently being negotiated between APVMA and registrants.
In Vietnam officers of Plant Protection Department prepared procedures for effective phosphine fumigation and submitted them to MARD for incorporation into the National Fumigation Standard.
Training programs
China: In 2001 QDPI&F and Grainco staff trained about 40 key scientists and storage managers in safe, effective use of phosphine and in adult education (extension) and implementation techniques. Chinese project participants then conducted training workshops for more than 3500 grain storage personnel with support from the State Administration of Grain.
Vietnam: Early in the project, staff of VIAEP completed a national survey of insect infestation rates and pest management practices undertaken by farmers, cooperatives and central storages in Vietnam, and the potential of fumigation with phosphine. This information was used to develop appropriate extension strategies and provided a baseline for measuring changes seen as a result of the project.
Researching and extending improved household storage techniques.
Surveys of the farm grain storage system revealed that fumigation with phosphine is, in most cases, not appropriate for farmers because of potential health risks. The researchers therefore realigned their extension and research effort to emphasise other management techniques. In Vietnam the VIAEPHT project team delivered 11 training courses, each for about 70 farmers, in seven provinces in the north and centre of the country. Topics covered: insect pest detection and damage, results of field trials, use of practical, effective cleaning, drying and storage methods. The team also produced a practical IPM manual for farmers. Experimental trials were set up in farm households and villages to introduce and demonstrate new technologies including storages and grain dryers. This team focused on introducing appropriate improvements to the lives of ethnic minority people living in mountainous regions where postharvest losses are typically 20% and can reach 40%. They trialled drying and storage methods that were affordable and compatible with village lifestyle and successfully reduced insect damage to about 5%.
Innovations to enhance the efficacy of phosphine fumigation
In China scientists at the Chengdu Grain Storage Research Institute defined levels of CO2 required for control of a wide range of storage pests. They also demonstrated the utility of applying phosphine as a split application and the use of CO2 to improve the efficacy of phosphine (by limiting sorption).
In Australia researchers at QDPI&F completed experiments and field trials characterising the influence of fumigation temperature, phosphine concentration and exposure period on the effectiveness of phosphine against resistant Rhyzopertha dominica and Sitophilus oryzae. Resistance to phosphine was also characterised in Tribolium castaneum and Oryzaephilus surinamensisboth resistances can be controlled with newly developed protocols.
Phosphine fumigations of grain in bag-stacks and in small bins generally result in exposure of insects to changing concentrations of gas rather than the more constant concentrations experienced in large storages. In Australia, a series of experiments undertaken at QDPI&F showed that the efficacy of changing concentrations of phosphine can be predicted from assays using constant concentrations. This result will allow a shortening of fumigation times
Determining the key factors preventing effective control of psocids with phosphine
Students at Henan University of Technology contributed outstandingly to the knowledge of psocid biology, ecology, distribution and resistance to phosphine. This work is a highlight of the project.