Haskap plants do not appear to be subject to many foliar diseases, however there are some issues of note.
From our experience, Botrytis – a fungal organism – is a disease of some significance. It can completely defoliate plants with new leaves during periods of high humidity or wet conditions. This is a common fungal disease found infecting strawberries, potatoes, tomatoes and nursery plants, especially when cool wet conditions prevail. A vulnerable time for Haskap plants is during the early rapid foliar growth stage when plant tissues are delicate and lush. At this stage wet windy weather can promote leaf and stem damage, setting an ideal stage for Botrytis infection.
Currently there are no label recommendations for use of fungicides, but you can prevent or limit infection by adequately pruning and spacing plants in-row to promote airflow, refraining from over-fertilizing plants, and eradicating infected tissues. We welcome visits to our plot to observe our pruning trial and to observe new clones that may have better Botrytis resistance.
Powdery mildew has also been reported as a potential disease issue (for which no fungicides are registered) though it is usually present later in the season after all fruit has been harvested. This disease appears after harvest and weakens the plant before winter, which can have a cumulative effect over time.
This disease attacks foliage and can turn a green plant into a mess in hours. The above photo demonstrates disease in an active state.