Fungicides effectively used for growth inhibition of several fungi could induce mycotoxin biosynthesis in toxigenic species.

Seven different commercial fungicides (Aliette, Rovral, Cantus, Ortiva, Luna Experience, Fenomenal and Mancozeb) were tested for their ability to inhibit the growth of the fungal species Penicillium nordicum, Penicillium verrucosum, Verticillium dahliae and Cladosporium sp. In case of the mycotoxigenic strains P. nordicum and P. verrucosum, the biosynthesis of the mycotoxins ochratoxin and citrinin was determined. Interestingly individual fungicides were only able to inhibit the growth of the analyzed fungi to some extent. In case of P. verrucosum the fungicide "Rovral", an iprodion belonging to the substance class of imidazoles, led to a decrease in the growth rate but to a strong induction of mycotoxin biosynthesis as has been described earlier for the strobilurins. Consequently before using a given fungicide to protect crops and enhance storage life, the applicability of this chemical compound should be tested not only for its ability to inhibit fungal growth but also for its effect on level of secondary metabolite biosynthesis.