Occurrence and progression of some foliar diseases of Soybean [Glycine max (L.) Merrill]

The results indicated that the highest value (361.63, 363.03 & 515.35, 445.85) of area under disease progress curve (AUDPC) of Alternaria leaf spot and target leaf spot were recorded on cv. JS 335 and Bragg which showed most susceptible, respectively during both the years. Rust was appeared one step later and their earlier symptom was initiated on cv. JS 335 which proved most susceptible with AUDPCs of 324.94 and 500.26 during 2011 and 2012. Observations recorded on meteorological factors and disease development revealed that the Alternaria leaf spot and target leaf spot were initiated in the first week of September during both the years with the occurrence of mean temperature of 24.42–30.44 & 24.3–30.7°C, RH of 67.71–83.71 & 58.6–85.0%, rainfall of 61 & 11.4 mm and sunshine of 4.07 & 4.29 hrs, respectively. The highest Alternaria leaf spot and target leaf spot were recorded by third week of October. The next disease was rust and initiated in first week of October. The disease progressively increased and obtained highest disease intensity in first week of November during 2 years with the occurrence of temperature from 20.7–29.65 & 23.24°C, RH from 47.29–82.94 & 48.04–83.76%, sunshine 7.82 & 8.28 hrs and rainfall 10.96 & 21.86 mm, respectively.