The fungus Alternaria macrospora causes a disease of cotton plants known as Alternaria leaf blight (or Alternaria leaf spot). Brown or black, irregular or circular patches on the leaves define this disease, which can affect cotton at either the vegetative or floral phases of development. Leaves initially impacted by the disease will eventually die when the spots join together to form bigger regions of blight. The cotton plants’ general health and output might suffer if the disease causes the leaves to become brittle and fall off.
Alterneria Leaf Blight Management in Cotton
The Causal Organism of Alternaria Leaf Blight
Leaf blight, or Alternaria leaf spot, is a fungal disease that affects plants and is caused by the fungus Alternaria macrospora. The Alternaria genus of Ascomycetes is responsible for various plant diseases affecting vegetables, fruits, and ornamental plants. Leaf spots and defoliation are symptoms of an A. macrospora infection, which begins in the lower leaves and moves upwards through the cotton plant.
The Disease Cycle of Alternaria Leaf Blight
Alternaria leaf blight is caused by the fungi Alternaria macrospora, which may survive on cotton scraps without living tissue or an alternative host. The infection spreads by producing airborne fungal particles and splashing water onto healthy plants. It causes the illness to proceed and the formation of leaf spots. The Alternaria leaf blight disease cycle begins with the fungus infecting the cotton plant’s leaves and generating spores within the leaf spots. These pieces can then travel to healthy plants, causing the illness to spread and infect other plants.
Causes/conditions Favorable for Alternaria Leaf Blight Disease Spread in The Field.
- Alternaria leaf spot of cotton is a fungal disease that causes fast defoliation and leaf spots in cotton plants. Warm and humid climatic conditions encourage the development of this disease, with temperatures around 27°C ideal for symptom development.
- In addition to favorable weather circumstances, physiological or nutritional stress might make the cotton plant susceptible to Alternaria leaf blight. Premature 1aging or a heavy fruit load might weaken the plant, leaving it more susceptible to disease.
Symptoms of Alternaria Leaf Blight Disease
- Alternaria leaf spot disease can occur at any stage of plant growth, but it tends to be more severe when the plants are between 45 to 60 days old.
- The symptoms of the disease can be seen in the form of small, brown, irregular, or round spots on the leaves.
- Each spot is characterized by a central lesion surrounded by concentric rings.
- Multiple spots can merge to form large, blighted areas on the leaves.
- The affected leaves become brittle and eventually fall off, leading to a reduction in the overall health and productivity of the plant.
- In some cases, stem lesions may also be seen.
- In severe instances of the disease, the spots may even appear on the bracts and bolls, causing further damage to the plant.