Tomato: efficacy of conventional fungicides, biofungicides and disinfectants for control of tomato leaf mould, Passalora fulva

 

Tomato leaf mould caused by Passalora fulva (previously Cladosporium fulvum) is a destructive foliar disease of increasing importance in the UK. Outbreaks have occurred most years over the last decade and affected a range of varieties. Previously well controlled by genetic resistance, the new outbreaks appear to be caused by the cultivation of varieties with no claimed resistance and the emergence of strains capable of overcoming the resistance genes deployed in current varieties. Amistar (azoxystrobin) has given good control in some crops, but grower reports indicate resistant strains can develop within a few years. The disease has also affected organic crops, where use of Amistar and other conventional fungicides is not permitted by the Soil Association. No plant protection products currently permitted on tomato carry a label recommendation for leaf mould control. Spores of P.fulva appear to be very resistant to dryness and low temperatures and are believed to survive in a dormant state from one crop to the next. The fungus can also survive saprophytically in dried leaf debris. There is little information on the relative effectiveness of different disinfectants in reducing inoculum of P.fulva. The aim of this study is to provide tools for improved management of tomato leaf mould in both conventional and organic crops through identification of effective chemical fungicide and biofungicide treatments for use in crops, and of biocide treatments for use between crops.