In October 2022, the APVMA reduced the omethoate MRL for mango from 2ppm to 0.1ppm (Schedule 20). Omethoate occurs as a break down product within a few days after dimethoate application. This change relates to the recommendations from the APVMA’s chemical review of dimethoate in 2017 and was based on residue data available at the time showing that omethoate residues above 0.1 mg/kg should not occur when the dimethoate label instructions were followed.
However, last season, exceedances of omethoate MRLs were picked up from mangoes and other commodities. In response, Biosecurity Queensland investigated the situation and found that the dimethoate applications were done as per label directions. Furthermore, their investigation didn’t find any patterns (pH, product manufacturers, age, additives, etc) that could explain the MRL breaches. The APVMA conducted a technical assessment of the new residue information relating to the post-harvest dip use of dimethoate on mangoes and consider there to be a consumer safety risk associated with the current label use.
The APVMA’s Chemical Review team will now determine the most appropriate course of regulatory action and will be communicating with industry in the near future.
While there may be growers who didn’t have problems with omethoate MRL exceedance last season, the APVMA’s assessment is based on worst-case scenarios. As a precautionary measure, it is likely the APVMA will suspend the post-harvest use of dimethoate for fruit fly control (ICA-01 and ICA-02). This will impact negatively on interstate trade of mangoes into South Australia, Tasmania and Western Australia.
Condition and Treatment of Mango (CTM-01) is accepted by South Australia and Tasmania and includes pre-harvest treatments (cover and bait sprays) to manage fruit flies as alternatives to post-harvest dimethoate dip or flood spray. Please refer to the CTM-01 operational procedure for more details.
The other ICA procedures approved by SA, Tasmania and WA to meet the fruit fly import requirement are:
Currently, CTM-01 is not recognised by Western Australia and therefore pre-harvest treatments to control fruit flies are not accepted. A request for WA to recognise CTM-01 has been submitted and is currently being reviewed.