Apple scab (Venturia inaequalis): Direct control using decision support systems (Biofruitnet Practice Abstract)

Summary in the original language of the document

Support systems such as RIMpro provide forecasts of infection events and assist farmers in the decision-making for higher efficacy of the treatments and better scab control.
Practical recommendation
Apple scab sprayings
• Preventive treatment prior to infection period: The freshly germinating ascospores are very susceptible to contact fungicide, so a preventive treatment can be implemented prior to spore ejection (Fig. 1, A).
o Until balloon stage (BBCH 59): copper (150-300 g pure copper/ha*) or copper + wettable sulfur (ex-change sulphur with a wetting agent when the temperature is low2); reduce the amount of copper as you get closer to the pre-bloom (risk of russeting).
o From balloon stage (BBCH 59) to walnut stage (BBCH 74)1: acidified clay mineral (8 kg/ha*) + wettable sulfur (8-12 kg/ha prior to full bloom BBCH 65, 3-8 kg/ha after full bloom, choose lower dosage if high temperatures*), or only wettable sulfur if acidified clay mineral is not allowed in your country*.
o From walnut stage on (BBCH 74): continue with acidified clay mineral + wettable sulfur*, or switch to copper (+ sulfur)*.
• Stop-treatment onto wet foliage: The amount of germinating ascospores over time is indicated by the white area behind the yellow bar (Fig. 1, 7). Within this time, a stop treatment can be used to kill the spores (Fig. 1, B).
o lime sulfur (25.6 l/ha prior to full Bloom, 19.2 l/ha after full bloom*) or
o potassium bicarbonate (4.8 kg/ha*) + wettable sulfur (8-12 kg/ha prior to full bloom BBCH 65, 3 8 kg/ha after full bloom, choose lower dosage if high temperatures2*)