Anthracnose
Registered against on 5 crops
Anthracnose, primarily caused by fungal species within the Colletotrichum genus (notably the Colletotrichum gloeosporioides and Colletotrichum acutatum complexes), is one of the most destructive fungal diseases affecting tree crops and horticulture across Australia. The pathogen attacks blossoms, foliage, twigs, and developing fruit, frequently establishing quiescent infections that break out during post-harvest storage and ripening.
For commercial growers in tropical, subtropical, and temperate production districts, anthracnose causes substantial financial losses through direct yield reduction, lowered fruit quality, and the rejection of domestic or export consignments. In high-value perennial orchards such as mango, avocado, and macadamia, latent infections carried into post-harvest supply chains can result in widespread fruit breakdown prior to retail sale.
Effective management requires an integrated approach that combines orchard sanitation, active canopy management, precise fungicide timing during susceptible crop stages, and careful post-harvest chain management to minimize fruit losses.
Where it matters in Australia
Anthracnose is a major disease across Australian horticultural and tree crop districts, particularly in tropical and subtropical regions such as the Atherton Tableland, Bundaberg, and the Northern Rivers, where warm summer rainfall creates ideal infection conditions. It also poses a seasonal threat in temperate fruit and vegetable growing regions during humid spring and summer weather. Key commercial host crops with registered protectant and curative products include mango, avocado, tomato, macadamia, and grape.
Symptoms
On leaves, anthracnose causes small, dark brown to black circular spots that often expand into irregular necrotic patches, leading to leaf distortion, tearing, or shot-holing along leaf veins. On floral structures, brown lesions quickly coalesce to produce panicle blight and heavy flower drop.
On green fruit, early latent infections may be invisible or appear as minor dark speckling or tear-staining patterns where rain washed spores down the fruit skin. As fruit ripens post-harvest, sunken, dark brown to black circular spots expand into the flesh. In humid conditions, bright salmon-pink or orange sticky spore masses appear in the center of lesions. Unlike soft rots, active anthracnose lesions remain firm and dryish until secondary decay organisms invade.
Life cycle
Anthracnose overwinters and carries over between seasons as dormant mycelium or appressoria within infected twigs, leaf litter, old floral panicles, and mummified fruit remaining in the canopy or on the orchard floor. Spores (conidia) are produced in gelatinous masses within microscopic fruiting structures during periods of warm, humid, or wet weather.
Spore transfer occurs predominantly via rain splash, canopy drip, and wind-driven rain. Primary infection takes place when spores land on young leaves, flowers, or developing green fruit during periods of high relative humidity or free moisture. Spores germinate to form appressoria that penetrate the plant cuticle and go dormant. Secondary infection cycles repeat rapidly during warm, wet summer conditions, continually generating fresh spore inoculum throughout the paddock or orchard.
Monitoring
Begin orchard scouting before flower emergence and flush, inspecting the canopy and orchard floor for carryover disease sources such as dead twigs, old flower panicles, and mummified fruit. During vegetative flush and bloom, inspect panicles, young leaves, and developing fruitlets weekly for water-soaked spots, dark speckling, or floral blighting.
Increase monitoring frequency during prolonged wet spells, high humidity events, or heavy dew conditions. Document disease incidence and canopy wetness duration in your spray diary. Assess post-harvest fruit lots to trace back field infections and evaluate the effectiveness of the season's management program for each block.
Management
Integrated anthracnose management relies on combining cultural sanitation, canopy architecture management, and well-timed fungicide programs:
- Cultural control: Prune trees after harvest to remove dead wood, old flower stalks, and diseased twigs, which drastically lowers carryover inoculum. Maintain open canopies to speed drying times after rain and facilitate thorough spray penetration. Manage crop nutrition to avoid excessive, dense foliage flushes that trap moisture. Remove fallen fruit and crop debris from under the canopy where practical.
- Harvest & Shed Handling: Harvest fruit during dry conditions, avoid skin tearing or physical bruising, and establish rapid post-harvest cooling and cold chain discipline to suppress fungal development.
- Chemical control: Apply registered protectant and systemic fungicides during vulnerable crop stages such as panicle emergence, flowering, fruit set, and early fruit growth. Rotate chemical mode-of-action groups in line with CropLife Australia resistance management guidelines. Always refer to the approved APVMA product label for crop registrations, spray timing, withholding periods (WHP), and application directions.
Crops with registered control options
Common questions
- How does latent infection influence spray timing for anthracnose?
- Because Colletotrichum fungi penetrate immature fruit cuticles and remain dormant until post-harvest ripening, chemical protection must be applied preventatively during sensitive crop stages like flowering and early fruit set, rather than waiting for visible lesions to appear.
- Why is canopy management critical for anthracnose control?
- Pruning opens up the canopy, increasing airflow and sunlight penetration to shorten leaf wetness duration—a key requirement for fungal spore germination—while ensuring thorough spray coverage throughout the foliage.
- How can I prevent fungicide resistance developing in my block?
- Implement chemical rotation strategies across different fungicide activity groups as recommended by CropLife Australia, combining protectant products with systemic options and maintaining sound cultural controls to lower overall disease pressure.
- Where can I find the correct withholding period (WHP) for my crop?
- Withholding periods and re-entry statements vary depending on the active ingredient, crop type, and application method. Always consult the approved APVMA label on the container for binding statutory requirements.
- Why do anthracnose fruit rot symptoms rapidly escalate after harvest?
- During fruit ripening, natural plant defense compounds decrease and fruit sugars increase, triggering dormant fungal structures (appressoria) to activate and invade the softening fruit tissue.