Alternaria leaf blotch is characterised by irregular red–brown coloured lesions on the leaves.
The lesions might expand under favourable conditions, followed by yellowing of the leaves and then defoliation of the trees.
Leaf lesions often exhibit blackish-purple borders.
Alternaria leaf blotch is distinguished by the fact that in favourable weather conditions the blotches will continue to grow, and when the leaf is half covered by lesions, it will tend to drop prematurely from the tree.
Alternaria fruit spot
Alternaria fruit spot is characterised by small, slightly sunken, light to medium brown spots appearing on the lenticels of the fruit, often surrounded by a black border.
Symptoms appear after warm weather and usually no earlier than 42 days before harvest.
Non-pesticide management
Due to the similarity of Alternaria leaf blotch and fruit spot symptoms to those caused by other problems (e.g. fungal diseases and physical damage), it is important to have symptoms assessed by an expert, especially if you are considering applying fungicides (or other treatments) to combat these symptoms.
Be particularly vigilant with apple varieties that are susceptible to Alternaria leaf blotch and fruit spot including Fuji, Gala, Pink Lady and Red Delicious.
The proposed management approach for Alternaria leaf blotch and fruit spot includes the removal or breakdown of leaf residue, in particular when leaf disease occurred in the previous season.
Download the Orchard plant protection guide
See this article in Tree Fruit Dec 2019
