WA CITRUS disease management 

Skill up on how to best protect your trees from diseases with tips from citrus pathologist Dr Nerida Donovan.

Words Rachelle Johnstone, DPIRD + Dr Nerida Donovan, NSW DPI

Dr Nerida Donovan, NSW DPI citrus pathologist, and orchard walk host Mick Mann in West Gingin.

THE Citrus Integrated Pest and Disease Management (IPDM) extension project team in WA has held two seasonal orchard walks with a focus on disease management this year. Growers and field staff from northern and southern production areas attended the events, which were held in Burekup and Gingin, with citrus researchers, local pathologists and crop advisors.

Dr Nerida Donovan, citrus pathologist from New South Wales’ Department of Primary Industries (NSW DPI), visited WA to present information on citrus diseases, including management options and exotic diseases. Nerida showed participants how to take samples for disease diagnostics and what information pathologists need to get a clear picture of a problem – they were:

• Speak to a plant pathologist, if possible.

• Send clear photos of the problem (symptoms on the tree or fruit), as well as the surrounding environment, such as the whole tree and trees nearby.

• Provide as much detail as possible, such as scion and rootstock variety, extent of the problem, soil type, irrigation and nutrition.

• Ask what type of sample to send and how to send it. Send samples earlier in the week to avoid extra time in transit over a weekend.

Participants learned about diseases and disorders affecting citrus in WA, such as anthracnose, phytophthora brown rot and black core rot, as well as key exotic diseases, such as HLB. Nerida also spoke on reducing infection levels in the orchard – they were:

• Prune trees annually to remove dead wood, improve airflow, reduce humidity, reduce spore load and lower the risk of spread from rain splash.

• Remove debris from tools and sterilise pruning tools with bleach between blocks.

• Ensure sprinklers are not too close to trunks and spray directly onto them, and keep trees well skirted to reduce leaf wetting.

• Source budwood and rootstock seed that are true to type and healthy to reduce the risk of introducing graft transmissible diseases.

• Apply pre‐harvest copper fungicides to protect fruit and foliage.

Nerida also gave an overview of several industry funded projects on citrus diseases, including work on black core rot. It identified a need for complementary IPDM tools for effective management of this fungal disease. The internal rot and bitter flavours of infected fruit often remain undetected until they reach a kitchen bench or juicing plant. To help with this work, please complete a grower survey (scan QR code below).

Several IPDM fact sheets have been produced as part of this project and are now available on the NSW DPI website under the ‘IPDM extension program’ tab. A recording of a webinar presented by Nerida on Managing Citrus Diseases with Copper is also available (see link below).

The Citrus IPDM extension project has been funded by Hort Innovation, using the citrus research and development levy and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

Click the button to complete the survey on black core rot.