FUMIGATION OF PADDY RICE AND RICE PRODUCTS WITH ETHYL FORMATE

The phasing‐out of methyl bromide (MB) has created a need for alternative fumigants to disinfest cereals such as rice. One possible alternative is ethyl formate (EtF). The interaction of EtF with barley, wheat and canola has been investigated previously, but more data on the fate of EtF during fumigation of rice commodities and its effects on their quality are needed. In this study, 5 kg samples of paddy rice, brown rice, white rice and rice flour were treated for 2 d with EtF applied at 60 g!m -3 at 10 and 25oC. The loss of EtF from the headspace during fumigation was then measured at regular intervals. EtF loss from headspace was especially high during fumigation of paddy rice and rice flour. Remaining fumigant was removed from the commodity by progressive airing. Removal of EtF from all commodities was rapid at 25°C compared to 10°C. After remaining gas concentrations fell below the threshold limit value, EtF residues were determined in all commodities and untreated controls. At 25°C, residues were indistinguishable from background levels. At 10°C substantial residues were detected immediately after airing off. To investigate phytotoxicity of EtF towards paddy rice, the viability of paddy rice after fumigation was measured. It was found that EtF treatment at 60 g!m -3 had no effect on the viability of paddy rice.