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

Summary in the original language of the document

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 (exchange 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*)