Brown rot

Description

Brown rot appears as a tan brown mould on the fruit surface, producing masses of spores and infected fruit can shrivel up to a mummy. Primary infection can cause blossom blight and infection of fruit, where it can remain dormant until pre-harvest when fruit sugar content increases. Ripe fruit which is picked with a dormant infection can develop spots in storage. 

Brown rot survives on twig cankers or mummified fruit on the ground from the previous year’s crop. During spring, conidial spores form on mummified fruit, and are spread by wind, rain and insects (e.g. Carpophilus beetle) onto blossoms and young shoots. Successful infection requires wet conditions and once infected, blighted blossoms produce conidia, providing a source of secondary inoculum onto immature and ripe fruit. Fruit with insect wounds or injury are more susceptible to infection.

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Control

Once established in an orchard, brown rot requires continual management. To reduce disease levels, remove rotten and mummified fruit and prune and remove infected twigs. Prune trees to maintain good airflow and allow sunlight in, which can delay fungal growth. Tightly bunched fruit can create conditions for the disease to thrive so where possible thin blossoms to control crop load. Controlling insects which may cause damage to fruit will reduce the susceptibility to brown spot.

Monitor crops and apply fungicide sprays preventatively to reduce primary infection. Curative fungicide applications should be aimed to coincide with critical infection times and a range of different modes of action should be used to prevent resistance. Post-harvest treatment of fruit can increase shelf life and help control further infections in storage.

Luna® Sensation is best applied from early blossom and/or at fruit ripening and is registered for the control of blossom blight and brown rot in stone fruit. Ziram Granuflo® can be applied from mid-full bloom and is also registered for the control of brown rot in stone fruit. 

References

Barry, K (Viewed Nov 2019), ‘Brown Rot Monilinia spp’, Tasmanian Institute of Agriculture, https://www.utas.edu.au/__data/assets/pdf_file/0006/1110399/Brown-rot.pdf

Department of Environment and Primary Industries (Viewed Nov 2019), ‘Brown-rot of stone fruits’, Agriculture Victoria, http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/fruit-and-nuts/stone-fruit-diseases/brown-rot-of-stone-fruits

Villalta, O, Holmes, R and Kreidl, S (Viewed Nov 2019), ‘Best practices for Brown Rot Management – Booklet’, Biosciences Research, Department of Economic Development, Jobs Transport and Resources, Victoria State Government, http://www.hin.com.au/__data/assets/pdf_file/0006/19437/Brochure-Brown-Rot-Best-Practices-HIA-SF12004-Aug-2015.pdf