Apple Scab, Venturia inaequalis, is a fungal disease of apples that attacks foliage, blossoms, and fruit. This disease is favoured by wet, cool conditions and has caused significant losses in the Okanagan region during years with high rainfall.
Apple Scab causing spores (Ascospores) overwinter on infected leaf litter on the orchard floor. These spores mature around the same time as green tip stage; they are released during rainy periods and can travel long distances in air currents. Spores land on leaves, blossoms and fruit, and under the right temperatures - if the leaves or fruit are wet long enough for the spores to germinate, a primary scab infection occurs.
Orchard Management Practices to Reduce Scab:
- Avoid the use of overhead watering
- Spraying protectants on a 7 to 14 day interval during primary scab season (typically peaks during blossom and ends by mid to late June)
- Back up protectant schedule with eradicant sprays, as necessary, to ensure adequate coverage during scab infection periods
Watch your scab model throughout this next week of predicted rainy weather - look for the red bars, indicating an infection period.