Ban hovers over Medfly chemicals

Lauren CelenzaCountryman

Mediterranean fruit fly (Medfly) control chemicals dimethoate and fenthion may not be permitted for use on edible skin fruit next season.

With the review for the widely used chemicals still ongoing, growers are anxiously waiting its release, fearing they will be taken off the shelf for good.

As chemical companies fail to come up with alternatives, industry bodies say growers need to switch to a system-based approach to tackle the pest.

Fruit West executive manager Gavin Foord said it was not yet known whether the chemicals would be phased out or if withholding periods would be lengthened, but industry needed to act now.

“The bottom line is we will have to change the way we manage Medfly in the future and a combination of trapping, baiting and cover sprays on an area wide-scale may be a workable option, ” he said.

Fruit West is working with the Department of Agriculture and Food (DAFWA) to secure a permit for the use of trichlorfon as part of the mix.

“We are also working with growers to utilise local expertise from DAFWA with the view of a good result for fruit growers and consumers, ” Mr Foord said.

Summerfruit Australia director Mark Wilkinson said dimethoate and fenthion were the most effective chemicals WA fruit growers had ever had.

“They have been around since the mid-1960s, they are a part of a group of organic phosphate insecticides that were highly effective, ” he said.

“They have very good systematic action — they get inside the fruit to kill maggots as well as the flies.”

Mr Wilkinson said that in the 1960s chemical toxicity was measured by animal testing and the levels were not accurate enough for government body the Agricultural Pesticide and Veterinary Medicines Authority (APVMA).

“There have been to my knowledge no cases of anyone becoming ill from eating fruit treated with these chemicals, but that’s not to say there isn’t a long-term adverse effect, ” he said.

“The APVMA wants hard evidence that stuff works and they want hard evidence that it’s safe.”

“In the past 15 years there has been a progression of reviews of the old chemistry to see if they meet the standards that the new chemistry has to meet.”

Mr Wilkinson said it was highly unlikely that growers would be able to use dimethoate on edible skin fruit again because the breakdown of the chemical into omethoate has shown to be much more toxic then previously thought.

Bayer Crop Science, the maker of fenthion product Lebaycid, says there is no “silver bullet” for a replacement.

Representative Tim Wilkie said there was no ready replacement, but they were working hard to find one.

“The residue obtained by eating a single piece of fruit that has been treated with the chemical Labacid has been shown to be above the safe limit, ” he said.

“We are searching for a Medfly treatment — we test 100,000 molecules each year, but so far haven’t had any luck finding a knock-down option.”

Mr Wilkie said one product called Calipso was being looked at as a Medfly control, however would need to be used in a system.

APVMA said a timeframe for the review’s release was not available.

“State government agencies, farming and commodity groups are involved in the National Response Plan to develop viable alternatives if there are changes to the use of these chemicals in Australia, ” a spokesman said.

DAFWA biosecurity director Shashi Sharma said the department was working closely with other states and national organisations to help prepare for likely change.

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