Incidence of Alternaria Leaf Blight in Tomato and Efficacy of Commercial Fungicides for its Control

摘要

A survey was conducted during 2000 and 2001 in the tomato growing areas in Punjab to assess the incidence of Alternaria leaf blight of tomato. The disease incidence ranged from 9.3 to 49.5% and 8.2 to 25.3% during the years 2000 and 2001, respectively. The per cent disease intensity was recorded maximum (49.5) at Tapa (District: Sangrur) in May on October transplanted crop during the year 2000 and minimum (8.2) at Bababakala (District: Amritsar) on November transplanted crop during the year 2001. Higher rainfall during the fruiting period (February-March) in 2000 than in 2001 appeared to be responsible for high disease incidence. Presence of Alternaria solani on the seeds (in vitro) extracted from the infected fruits ranged from 2.75 to 4.75%, though the seeds collected from healthy fruits were free from infection. The disease intensity was more on variety Punjab Chhuhara than on Punjab Upma. Among the 20 genotypes, none was found to possess complete resistance against A. solani under artificial inoculation by conidial suspension (10~4/ml). Out of eight fungicides, Dithane M-45 @ 0.25% was found to be the most effective in controlling A. solani, followed by Kavach @ 0.25%.