Angular leaf spot

Angular leaf spot is a bacterial disease in persimmons that produces sharply defined, angular lesions on leaves, often leading to premature defoliation and reduced fruit quality. It is caused by Cercospora species and Pseudocercospora species.

Disease identification

Angular leaf spot will show as straight-edged leaf spots that are found on infected persimmon foliage. Spots range in size up to 7 mm, with dead tissue in the centre and a green halo. The spots sometimes merge as the disease progresses, forming large necrotic areas. The shape of the leaf spots can be used to differentiate angular leaf spot infections from another important pathogen in persimmons, Mycosphaerella spp., which results in similar leaf spots but with round margins.

Damage

The disease is favoured by wet growing seasons, especially in Qld and NSW. Differences in varietal susceptibility have been reported, with the Izu cultivar being particularly vulnerable. Severe leaf infections can lead to yellowing, premature leaf fall and lost photosynthetic capacity, affecting fruit growth and carbohydrate reserves for the following season.

Monitoring

Angular leaf spot is most likely to be in persimmon orchards from shoot extension to just before harvest. Start random leaf inspections in early spring and continue weekly throughout the season. Inspect all varieties to ensure any varietal differences are seen. Identifying the infection early will help target treatments before it becomes too severe.

Management

Cultural and physical: Cercospora spores survive over winter on infected leaves and leaf stalks for 5–6 months and are a source of inoculum for infections in the following season. Therefore, good orchard hygiene to remove or destroy fallen leaves by thoroughly mulching will help reduce the disease potential. The fungus is spread by rainfall and is thought to be favoured by dense canopies and high humidity.

Pruning trees to encourage an open canopy will speed up drying, reduce humidity and allow for good spray penetration and coverage.

Chemical: refer to the APVMA PubCRIS database (https://portal.apvma.gov.au/pubcris) for registered controls.

Reference

George A, Nissen B, Bignell G, Hutton D, Broadley R and Dunn D (2017) Integrated pest and disease management manual for persimmon, second edition. Department of Agriculture and Fisheries, Queensland, https://www.horticulture.com.au/Information-Hub/Our-Projects/Project-Reports/PR13007