Impact of planting dates on population dynamics and seasonal incidence of onion thrips and purple blotch

Understanding of population dynamics and seasonal incidence of pests and foliar diseases is very useful in initiating appropriate control measures for successful cultivation of onion. Field experiments were conducted at AINRP on Onion and Garlic, Sambalpur, Odisha during Rabi season of 2012-13 revealed significantly minimum thrips population (8.50 & 9.52 thrips/plant) was recorded during 1st July, which gradually increased with advancement in date of planting, maximum being with 15th January planting (42.33 & 52.89 thrips/plant) while significantly higher total bulb yield of 214.00 to 217.15 q/ha was recorded with 15th October to 15th November planting as against 295.18 to 331.29 q/ha with 1st October to 15th November planting under unprotected and protected condition, respectively. Significantly minimum incidence of purple blotch was recorded when planted between 1st September to 15th October under both protected (36.40 to 42.57%) and unprotected (40.35 &44.67%) with total yield of 258.87 to 270.06 q/ha (15th October & 1st November) and 284.29 to 304.28 q/ha (1st October to 15th November), respectively. It may be concluded that under Odisha condition, transplanting of Rabi onion should be completed within 15th of November, preferably to obtain higher bulb yield with lower incidence of disease and pests.