DISEASE NOTES OR NEW RECORDS: Apparent degradation of pyrimethanil by Botrytis conerea and other fungi on agar plates is caused by migration of the fungicide within the agar medium

Apparent degradation of pyrimethanil was observed when a number of fungal pathogens were grown on Tinlines Minimal medium supplemented with the fungicide Scala. Degradation was suspected after development of a zone of clearing around the site of inoculation on agar plates indicated disappearance of the fungicide. Once cleared, fungal growth occurred within the zone. Gas Chromatography/Mass Spectrometry analysis of extracts from agar plates that had been colonised by Botrytis cinerea Pers. and other fungi indicated that the fungicide had not been degraded, but had concentrated at the edges of the Petri dish away from the point of growth. The physical basis of this fungicide mobility within the agar medium cannot be explained but is presumably due to metabolic activity of the growing fungal mycelium.