author(s)
Matangi Mishra and U Mukherjee

abstract
A mustard variety Pusa Mustard -25 was grown as test crop. The sowing of crop was done on 30^th of November in both the years namely 2017-18 and 2018-19. The crop was grown in 100 square metre plot as per the recommended agronomic practices without the application of insecticides. at T.C.A., Dholi (Muzaffarpur). The observations were recorded daily in both the crop seasons that is, 2017-18 and 2018-19. In the year 2017-18, it was found that the population of mean number of mustard aphid population initially, was 12.9, in the fourth standard week. It gradually increased from 18.2 to 30.4 in the fifth standard week to sixth standard week respectively. The population attained its peak in the ninth standard week that was 69.8 and after that it declined gradually and in the thirteenth standard week it was only 4.2. In the year 2018-19, the mean population of mustard aphid was 3.7 initially in the fourth standard week. It increased gradually from 8 to 46.6 from the fifth standard week to eighth standard week respectively. The peak of mean aphid population was 46.6 in the eighth standard week and after that the population started declining from 34.8 to 21.4 and lasted to 2.2 in the sixth, seventh and thirteenth standard week respectively. The correlation table shows that in both the years that is in 2017-18 and 2018-19, there was a negative correlation of aphid population with the aphid maximum and minimum temperature and it was non- significant. The relative humidity (RH) was also found non -significant. There was not any correlation of aphid population with the rainfall.