Vol. 10, Issue 11 (2021)

Author(s):
Rajaswaminathan Vairavan, Latha Paramanandham, Harish Sankarasubramanian and Kalaiselvi Thangavel

Abstract:
Cotton leaf spots are caused by various fungal pathogens, which are ubiquitous. These fungal leaf spots lead to a 30% loss of cotton production. To assess the disease incidence in Tamil Nadu, a survey was conducted to calculate the per cent disease index (PDI) for the leaf spot disease present in different locations of Tamil Nadu. PDI was calculated for the fungal leaf spot disease present in the cotton crop at 18 different locations from Coimbatore, Tiruppur, Dindigul, Madurai, Virudhunagar, and Permabalur districts. The PDI of the leaf spot disease varied between a range of 8.5-19.8. The highest PDI of 19.8 was recorded at Arasaappapillaipatti village of Dindigul district. The least PDI recorded was 8.5 at K. Kallampatti village of Madurai district. The major fungal leaf spot disease observed were Alternaria leaf spot, Myrothecium leaf spot, and Cercospora leaf spot. The occurrence of leaf spot in different locations expressed the presence of disease prevalence in Tamil Nadu, and strategies need to be taken to manage further disease spread.