Symptoms: Vary according to host, but often appear initially as small water-soaked flecks on lower leaves, enlarging into circular or irregularly-lobed lesions. Lesions typically become brown-black, and may or may not display concentric rings (the darker bands contain spores of the fungus). Lesions are sometimes surrounded by a chlorotic halo. Older leaf spots may become papery or brittle, leading to tearing and/or the development of ‘shot-hole’ symptoms. In some cases, spots coalesce to cover large areas, resulting in blighting of foliage. Alternaria spp. may also cause a range of other diseases including crown, stem and fruit rots.

An initiative of the National Nursery Industry Biosecurity Program (NY15004) and the ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project (NY15002).