Control Measures to Manage Alterneria leaf blight in Cotton

Alternaria leaf blight, caused by the fungus Alternaria macrospora, is a foliar disease that can affect cotton plants. It is one of the several diseases that can impact cotton crops, potentially leading to yield losses if not managed effectively. 

• Type of Infestation: Disease
• Common Name: Alterneria leaf blight 
• Scientific Name: Alternaria macrospora 
• Category of Plant Disease: Fungal Disease
• Mode of spread: Wind, Rain
• Affected parts of plant: Leaves, Stem, Fruit

Favorable factors for disease/Pest Development:

• Warm temperatures: The fungus thrives in temperatures between 20-30°C (68-86°F). High temperatures during summer months accelerate fungal growth and spore germination.
• High humidity: Humid conditions above 70% relative humidity provide a moist environment for spore survival and facilitate their dispersal through wind and splashing water.

Initial Symptoms:

• Pinpoint Spots: The first whispers of the disease appear as tiny, pinhead-sized, circular to oval spots scattered on leaves.

• Brown Lesions: These initial spots gradually expand, forming brown lesions with well-defined margins, often exhibiting concentric rings, resembling a target.

• Early Defoliation: In some cases, particularly under favorable conditions for the fungus, premature leaf drop can occur at this stage, starting with older, lower leaves.                

Severe Symptoms:

• Extensive Blighting: The initially scattered lesions coalesce, covering significant portions of the leaf surface, leading to extensive browning and blighting.

• Leaf Distortion: Infected leaves become distorted, curling upwards or cupping inwards, hindering efficient light capture and photosynthesis.

• Stunted Growth: The combined effects of defoliation and reduced photosynthesis lead to stunted plant growth, significantly impacting yield potential.

Control measures for Alterneria leaf blight  in Cotton: