Incidence of cabbage butterfly, Pieris brassicae Linn. across different sowing dates on cabbage

摘要

Impact of various sowing dates of cabbage during August (1st, 15th and 29th) and September (12th and 26th) 2002-03 were evaluated in relation to incidence of Pieris brassicae at Jammu, India, on cabbage crop. The larvae of Pieris brassicae appeared after fifth week after transplanting in the first date of sowing and remained active for a period of 18 weeks. The peak larval population per plant in the first, second, third, fourth and fifth sowing was recorded at 13th (31.4), 9th (33.32), 8th (32.3), 10th (65.7) and 7th (63.3) week after transplanting. The highest mean larval population per plant (28.4 larvae) was recorded in the crop sown on 12th August. It was evident that the crop sown on August 29th was found superior to all other sowing dates with a mean minimum pest population (13.3 larvae/plant) and highest marketable yield (155.6 q/ha).