✅ Causal Organism
- Teleomorph: Glomerella cingulata
- Anamorph: Colletotrichum
gloeosporioides
This fungus also causes bitter rot of
apple, making it a serious dual threat.
🔍 Diagnostic Symptoms
1. Leaf Symptoms
- Small, circular to irregular brown
spots with purple to dark borders.
- Spots often coalesce, leading to
large dead patches.
- Often surrounded by a chlorotic
(yellow) halo.
- Premature defoliation is common,
especially in hot and humid weather.
2. Fruit Symptoms (when present)
- Small, sunken lesions similar to
bitter rot.
- Lesions may ooze a pinkish spore
mass in humid conditions.
3. Shoot Symptoms
- Occasional lesions on young shoots,
but less common.
🌱 Overwintering
- The pathogen overwinters as:
- Dormant mycelium or fruiting
bodies (acervuli) in infected leaves, twigs, and mummified fruits.
- Can persist in fallen leaves and twig
cankers on the orchard floor or tree.
- In spring, conidia and ascospores
are spread by rain splash and wind to infect new tissues.
🛡️ Disease Management Strategies
🔁 Integrated Management Approach
1. Cultural Practices
- Sanitation:
- Remove and destroy fallen infected
leaves and pruned twigs.
- Remove mummified fruits
post-harvest.
- Pruning:
- Open the tree canopy to improve
air circulation and sunlight penetration.
- Prune out infected shoots.
- Orchard Floor Management:
- Mow or mulch to speed up leaf
litter decomposition.
2. Chemical Control
- Fungicides: Apply
protective sprays especially during pre- and post-bloom and summer rains:
- Captan
- Mancozeb
- Ziram
- Thiophanate-methyl
- Strobilurins (like azoxystrobin)
- Follow preventive spray programs
based on weather forecasts and past disease history.
3. Resistant Varieties
- Some cultivars like ‘Golden
Delicious’, ‘Gala’, and ‘Fuji’ are more susceptible.
- Use of less susceptible cultivars
where GLS is a major issue may reduce disease pressure.
4. Post-Harvest
- Proper handling and storage
conditions to avoid fruit rot caused by the same pathogen.
⚠️ Note
- GLS is easily confused with other
foliar diseases like Alternaria blotch or frog-eye leaf spot, so accurate
diagnosis is key—often confirmed via lab identification or microscopic
examination.
- For detailed explanation about symptomatology please refer to NC State university extension Apple Pathology Fact Sheet
