Symptoms:

1. Leaf Spots: The primary symptom of ACLS is the development of small, chlorotic spots on the leaves of infected apple trees. These spots may later turn necrotic, leading to the formation of dark lesions.
2. Leaf Deformation: Infected leaves may become distorted or curled as the disease progresses.
3. Premature Leaf Drop: Severe infections can cause premature defoliation, leading to reduced photosynthesis and overall tree vigor.
4. Reduced Fruit Quality: In addition to affecting foliage, ACLS can also lead to blemishes on fruit, reducing its marketability and quality.

Recommendations:

1. Cultural Practices: Implement good cultural practices such as proper pruning, adequate spacing between trees, and removal of fallen leaves to reduce disease pressure.
2. Resistant Varieties: Plant apple cultivars that are resistant or tolerant to apple scab and other diseases.
3. Fungicide Applications: Apply fungicides labeled for apple scab control according to recommended timing and dosage, especially during periods of high disease pressure.
4. Sanitation: Remove and destroy infected leaves, branches, and fruit to reduce the inoculum source and prevent disease spread.
5. Avoid Overhead Irrigation: Minimize overhead irrigation to reduce leaf wetness and humidity, which can favor disease development.
6. Monitor: Regularly monitor apple trees for symptoms of disease and take appropriate action if detected.

Causes:

1. Fungal Pathogen: Apple Chlorotic Leaf Spot is caused by the fungus Venturia inaequalis, which overwinters in infected plant debris and produces spores during favorable conditions for disease spread.
2. Moisture and Humidity: Wet and humid conditions, especially during spring and early summer, create ideal conditions for the development and spread of apple scab.

Preventive Measures:

1. Resistant Cultivars: Plant apple varieties that are resistant to apple scab, if available.
2. Sanitation: Properly dispose of fallen leaves and fruit to reduce the overwintering of the fungal pathogen.
3. Fungicide Treatments: Apply fungicides preventively or as soon as symptoms appear, following label instructions carefully.
4. Pruning: Prune apple trees to improve air circulation and sunlight penetration, which can help reduce humidity and minimize disease pressure.
5. Avoid Wet Conditions: Minimize leaf wetness by avoiding overhead irrigation and planting apple trees in areas with good air drainage.

By implementing these recommendations and preventive measures, apple growers can effectively manage apple scab and reduce the impact of diseases like Apple Chlorotic Leaf Spot on their orchards. It’s important to note that consulting with local agricultural extension services or experts is advisable for accurate diagnosis and management strategies tailored to specific regions and conditions.