Effects of naled and dichlorvos on growth and production of Luteoskyrin byPenicillium islandicum.

Two organophosphorus insecticides, 1, 2-dibromo -2, 2-dichloroethyl dimethyl phosphate (naled) and dimethyl 2, 2 -dichlorovinyl phosphate (dichlorvos) were used for investigation of their effects on growth and production of luteoskyrin mycotoxin byPenicillium islandicum in various cultural media at 25°C for 30 days or 60 days. When the concentration of naled and dichlorvos in Czapek solution broth reached 5mg/50mL, growth and production of luteoskyrin by the fungus was completely inhibited. In unpolished rice medium, 15mg/50g of naled was required to retard fungal growth, while the concentration to inhibit the biosynthesis of luteoskyrin was 10mg/50g. On the other hand, if the medium contained dichlorvos at the level of 30mg/50g, the ability to produce luteoskyrin byP islandicum was significantly reduced. In the unhulled rice case, both naled and dichlorvos at the concentration of 15mg/50g were necessary to retard the fungal growth, and 1 mg/50g of each compound exhibits its ability to inhibit the toxin production. Furthermore, it was also found when the cultural medium contained only small amounts of naled and dichlorvos [0.5mg/50g (mL)] the capability to synthesize luteoskyrin by the fungus was drastically reduced. These data strongly suggest that both naled and dichlorvos have similar ability to inhibit luteoskyrin biosynthesis byP islandicum and are also able to retard the fungal growth.