An Evaluation of Scab Control (Venturia inaequalis) Using Sulphur as an Organic Fungicide on 'Bramley's Seedling' Apple in Ireland

The 'Bramley' apple is one of the oldest and currently the most important apple cultivar in Ireland at around sixty thousand tonnes per year. During the 1920s, the 'Bramley' became susceptible to apple scab (Venturia inaequalis) and a full fungicide protection programme is now required to ensure a commercial crop. The Irish maritime climate is particularly suitable for apple scab development. Under current organic regulations only two fungicides have recommendations for use in Ireland - copper and sulphur. Copper is a heavy metal toxin and its use is gradually being restricted in the European Union. It was decided to evaluate a sulphur based programme on 'Bramley's over a full growing season. Elemental sulphur (Microthion Special) was compared with a full scab protection programme under the standard agrochemical evaluation programme. The standard plots produced 160 kg of commercial quality fruit compared to the sulphur treated plots which produced 76 kg (a reduction of 53%). Fruit set and fruit size were lower in the sulphur treated plots while leaf scab infection rate was higher. From these results it is evident that sulphur alone is not sufficient for adequate scab control on 'Bramley' apples produced under organic conditions in the Irish maritime climate.