Apparent degradation of pyrimethanil by Botrytis cinerea 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 p athogens were grown on Tinlines Minimal medium supplemented with the fungic ide Scala. Degradation was suspected after development of a zone of clearin g around the site of inoculation on agar plates indicated disappearance of the fungicide. Once cleared, fungal growth occurred within the zone. Gas Ch romatography/Mass Spectrometry analysis of extracts from agar plates that h ad been colonised by Botrytis cinerea Pers. and other fungi indicated that the fungicide had not been degraded, but had concentrated at the edges of t he Petri dish away from the point of growth. The physical basis of this fun gicide mobility within the agar medium cannot be explained but is presumabl y due to metabolic activity of the growing fungal mycelium.