Sensitive technology tightens residues compliance

Food safety concerns returned the focus to chemical residue issues at this year’s Australian Grain Storage and Protection Conference

The increasing sophistication of chemical detection equipment now makes it relatively commonplace to detect as little as an egg-sized quantity of chemical – about 60 grams – spread through a 60,000-tonne Panamax shipload of grain. And some equipment can measure as little as a teaspoon of chemical in the same load.

Rising food-safety concerns, combined with increasingly sensitive testing, were front and centre issues when more than 160 grains industry members from all parts of the supply chain came together at the annual Australian Grain Storage and Protection Conference in Melbourne in June.

The National Working Party on Grain Protection (NWPGP) hosted the conference, in conjunction with Grain Trade Australia.

Stored-grain pests had a lower profile at this year’s conference as a comparatively dry season resulted in fewer infestations around the country. Recent changes to fumigant protocols have also improved the industry’s capacity to deal with resistant insects, particularly at bulk-handling facilities.

For growers, the messages remained – the need to use gas-tight silos when fumigating and the need for regular monitoring of grain in storage. However, chemical contamination and international compliance issues dominated several presentations.

Residue results

Image of two men at a conference

Retiring chair of the National Working Party on Grain Protection Bill Murray (left) and his successor Gerard McMullen.

PHOTO: Brad Collis

The director of the National Residue Survey (NRS), Ian Reichstein, reported on the 2014-15 grain-residue monitoring program, which tested 6239 samples nationally.

Compliance with maximum residue limits (MRLs) on the 200 chemicals tested was 99.86 per cent from 3452 bulk-export samples. This was up from 99.7 per cent the previous year. The 2034 export container samples achieved 98.77 per cent compliance (98.9 in 2013-14).

On the domestic front, 753 samples were tested with compliance of 97.48 per cent (97.5 in 2013-14). Mr Reichstein said contamination occurred more frequently in domestic grain because it was more commonly delivered direct from the farm in smaller parcels

There was 100 per cent compliance for the 100 samples collected for mycotoxin analyses.

Despite this excellent result, Mr Reichstein indicated that there were a couple of concerns that warranted industry attention. He said haloxyfop herbicide residues were a continuing problem, despite changes to product labels in October 2014 to prevent applications late in the growing season, which were contributing to MRL breaches.

Flutriafol residues have also continued to raise a ‘red flag’.

Fertiliser contamination

The NRS began monitoring for the fungicide flutriafol in 2004 and there has been a big increase in the number of detections and contraventions in the past five years. Contamination can occur when grain comes into contact with flutriafol-treated fertiliser used as a seed protectant, or in wheat that has been treated for rust late in the growing season.

Mr Reichstein told the conference there had been no discernible reduction in the incidence of flutriafol residues exceeding the MRL. Trace-backs showed contamination was most commonly the result of back-loading flutriafol-treated fertiliser deliveries with grain, or from equipment coming into contact with the treated fertiliser.

Ongoing flutriafol contamination has also flagged the potential of general fertiliser contamination as an issue. The NRS has not previously routinely tested for fertilisers.

In an attempt to set a baseline for nitrogen and phosphorus in grain, the NRS compared flutriafol-affected samples against several unaffected samples earlier this year. Mr Reichstein said several of these other samples showed elevated levels of nitrogen, indicating likely fertiliser contamination. One sample had visible traces of fertiliser.

In response to these concerns delegates at the conference endorsed specific testing of up to 500 samples of grain in the 2015-16 NRS to identify the extent of fertiliser contamination.

Commenting after the conference, Mr Reichstein said Taiwan had already reported a flutriafol MRL breach in a container of Australian grain. Importers are now testing for these kinds of contaminants, he said, and their presence could jeopardise trade.

He added that domestic grain was equally at risk of fertiliser contamination as transport arrangements for deliveries meant grain was likely to come into contact with trucks that had carried fertiliser in a prior load and were often unloaded directly at a packing or processing site.

Improved truck hygiene could help eliminate basic fertiliser contamination and, with it, flutriafol contamination.

However, Victorian state chemical officer Steven Field told the conference there was no fully effective, documented way to decontaminate equipment that had been in contact with flutriafol-treated fertiliser. This includes trucks, as well as on-farm equipment such as augers and silos where treated fertiliser may have been stored.

“It is a problem that we need to address by further research and making changes to the current transport codes of practice,” Mr Field said.  

Phosphine alternative

In another presentation, CEO of the Plant Biosecurity Cooperative Research Centre (PBCRC) Dr Michael Robinson reported on the development of a synthetic silica product as an alternative to phosphine.

He said it was a possible game-changer for the industry. Laboratory tests showed 100 per cent insect kills in five to 10 days.

Field trials have begun and there are several challenges, such as application technologies and registration. However, he was optimistic that a new product for grain protection could be brought to market in three to four years. The PBCRC has applied for an international patent and the product is in development with commercial partners.

Other PBCRC projects include research into the benefits of aeration for stored grain, which has suggested possible fumigant savings of $2/t.

Work is also continuing on low-oxygen atmospheres to kill insects, particularly through the displacement of oxygen with nitrogen gas.

Dr Robinson said researchers were investigating insect responses to nitrogen, the effects of nitrogen on grain quality, and improvements in nitrogen generation technology that might make it easier and cheaper to use.

In partnership with Kansas State University in the US, the PBCRC is also investigating the use of ozone and chlorine dioxide as alternative insect treatments.

Another project completed in 2014 modelled how pests and pathogens might arrive in Australia on air currents associated with extreme weather events. This included modelling how the rust fungus Ug99 could be carried to Australia from South Africa. Dr Robinson said the PBCRC hoped to extend this work by developing surveillance strategies to monitor weather events as possible paths for pest and disease incursions.

International limits

The Australian Grain Storage and Protection Conference also paid tribute to the long-serving chair of the NWPGP Bill Murray, who has retired after 16 years as chair and 42 years on the working party (see Honours stack up for clean grain champion).

Gerard McMullen has taken on the role of chair, which includes leading Australia’s grain representation to the Codex Committee on Pesticide Residues (CCPR) to secure international MRLs that are comparable to Australian standards.

NRS team member Chris Williams, who is also an Australian CCPR delegation member, reported on international residue issues, including MRL breaches reported by importers for fenitrothion, piperonyl-butoxide, haloxyfop and paraquat, among others.

He said South Korea was also revising its residue-approval system for pesticides and was proposing to remove some MRLs, which would only be reinstated for chemicals on which the country had conducted its own toxicological risk-assessments.

In the absence of an approved MRL, the default level of 0.01 milligrams per kilogram of grain would apply.

Mr Williams said the NRS and the NWPGP would continue to seek clarification on the South Korean changes; however, government-to-government discussions may be needed to resolve the issue.

More information:

National Working Party on Grain Protection;

Ian Reichstein, National Residue Survey,


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