The sensitivity of Botrytis cinerea Pers.:Fr. to pyrimethanil in Croatia

From 1997 to 1999, we conducted a trial in vineyard in order to investigate the efficacy of the new active ingredient pyrimethanil against Botrytis cinerea. The pyrimethanil showed excellent efficacy applied alone during the season and also applied in alternations with other fungicides. We also assessed the risk of B. cinerea resistance build up to pyrimethanil in vitro and in vivo. The in vitro sensitivity of B. cinerea was tested by germ tube assay at 1 mg/l of pyrimethanil. The isolates that gave great numbers of Ra2 spores in in vitro assay were tested in vivo but neither of them showed > 50 % growth at 100 mg/l. Although the strains of B. cinerea resistant to pyrimethanil were determined, there is still no danger of the appearance of practical resistance at the trial site at Kutjevo. The obtained results are the confirmation of the FRAC warning that pyrimethanil is a high risk for resistance development so it is important that it is used in a carefully designed antiresistance strategy.