Circular leaf spot

Circular leaf spot is caused by Mycosphaerella spp. and was first identified in persimmons by NSW DPIRD in 2003. As the symptoms are similar, this leaf disease is often confused with angular leaf spot, which is also found in persimmons.

Disease identification

Infected persimmon foliage will have large circular spots with green halos. However, the lesions are generally larger and more rounded (i.e. not constrained by the leaf cell or vein structures) than with angular leaf spot.

Damage

Circular leaf spot is a major problem, especially in wet seasons, and particularly in northern NSW and the Sydney basin growing regions. It can lead to reduced photosynthetic capacity and premature leaf drop, which can affect fruit size in the current season and carbohydrate accumulation for the following season.

Monitoring

Circular leaf spot is most likely to be in persimmons from shoot extension to just before harvest. Start random leaf inspections in early spring and continue checking weekly throughout the season. Make sure all varieties are included to ensure any varietal differences are captured. Identifying the infection early will help to target treatments before it becomes too severe.

Management

Cultural and physical: circular leaf spot 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 and destroy fallen leaves 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.

Biological: there are currently no biological control treatments available for circular leaf spot.

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

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