The 8th International Conference on Controlled Atmospheres and Fumigation in Stored Products

The 8th International Conference on Controlled Atmospheres and Fumigation (CAF) in Stored Products was held 21-26 September 2008 in Chengdu, China. These conferences have two important functions: they provide a forum for reporting the latest advances in CAF technologies, and they encourage knowledge exchange between government authorities, research agencies and industry. The breadth of papers ranges from basic research to regulatory issues such as workplace health and safety and quarantine standards.

The conference was attended by close to 400 delegates and presentations were divided into ten sessions, all of which were plenary – allowing all delegates to see every paper over four days. The fifth day consisted of a visit to a large grain storage which uses CO2 to disinfest and preserve the grain (with a short visit to the Chengdu Panda Research Centre on the return trip).

At the conference there were 14 ‘Trade Exhibitors’, one of which was the CRCNPB (Fig.1). The CRC was promoted with a banner in Chinese showing the CRC logos and programs. There was also a full page, colour copy of our pamphlet in the Conference handbook.

The Australian contribution to the conference was outstanding, particularly the six presentations given by CRC members.

The following are notes synthesising the important points and themes that emerged from the conference:

Fumigants:

• Methyl bromide - scrubbing and disposal of to comply with the Montreal Protocol;
• Ozone - demonstrating successful use on small scale, specialised commodities but difficulties on large scale, e.g. treatment of 990 tonne wheat required 23 generators.
• Ethanedinitrile to control cereal pathogens;
• Ethyl formate – failure to control insects when applied as a liquid emphasising the necessity to apply this material in the vapour phase to avoid excessive sorption and ensure distribution. Successful use with fruit for surface disinfestation;
• Botanical fumigants – although many are toxic to insects, generally readily sorbed by grains greatly reducing activity. Also, high cost of production makes them impractical unless produced by the farmers in developing countries for their own use;
• Sulphuryl fluoride – successful replacement for methyl bromide in empty warehouses and mills. Fumigation of grain effective against non-egg stages. Weak against Tribolium. No data on efficacy against Cryptolestes ferrugineus. Also, emphasis on short-term fumigations. There is a need for laboratory evaluation of sulfuryl fluoride against phosphine-resistant biotypes such as flat grain beetle, especially exploring longer fumigation times (>4 d).
• Phosphine - Many papers on the practical application, particularly to manage resistance which is a world-wide phenomenon. Several papers supported recirculation in sealed storages as the most effective application system. The need for gas-tight storage was emphasised.

Flat grain beetle, Cryptolestes ferrugineus, biotypes possess highest resistance to phosphine. Chinese researchers recommended 200-350 ppm fumigations at 14-28 days, depending on temperature, for control of resistant flat grain beetle. These results are in line with the protocol being developed by the CRCNPB.

Khapra beetle larvae from Pakistan required 800 ppm phosphine for 15 days for complete control at 35C.

It was disappointing, though not unexpected, that no new methyl bromide replacement fumigant was put forward.

Engineering:

Interesting work being undertaken in USA on predictive modelling of mill fumigation. Most important influences on performance are sealing (gas-tightness) and wind speed and direction. Monitoring of phosphine gas movement in open-topped concrete silos in USA revealed that if grain temp was higher than the outside air temp, the gas moves up the silo, if grain temp is lower than the outside air temp then phosphine moves down through the grain in the silo.

Controlled and modified atmosphere:

Carbon dioxide – effective for insect control in grain, limited by cost. General dosage: >35% for 15 days.
Nitrogen – Use in transport containers,
Hermetic storage – effective for niche uses such as cocoa beans, chilli, or where insect contamination standards are lower, e.g. feed maize.

International linkages:

A paper presented by grain storage research leader, Dr Nui Xinghe, highlighted Chinese-Australian cooperative research in stored grain protection undertaken since the 1990s. A strong relationship was also forged with the United States Department of Agriculture/Kansas State University stored products centre in Manhattan, Kansas. Both groups are enthusiastic to discuss future research partnerships. Please contact me if you are interested p.collins@crcplantbiosecurity.com.au.
 

Fig.1: Pat Collins attending the CRCNPB both at the 8th International Conference on Controlled Atmospheres and Fumigation.