none Diaeretus rapae; HEMIPTERAN-HOSTS; Lipaphis erysimi; Prevalence related to mustard plant sowing date; MADHYA-PRADESH; Jabalpur; Prevalence on hemipteran host, effects of mustard plant sowing date Lipaphis erysimi; HYMENOPTERAN-PARASITES; Diaeretus rapae; Parasite prevalence related to plant host sowing date; PLANT-HOSTS; Mustard; Hymenopteran parasite prevalence related to sowing date; MADHYA-PRADESH; Jabalpur; Hymenopteran parasite prevalence related to plant host sowing date The find out the effect of time of sowing on the incidence of mustard aphid, Lipophis erysimi (Kalt.) (Homoptera : Aphididae), its endoparasite, Diaeretus rapae M' Intosh (Hymenoptera : Braconidae), and on yield, 'Varuna' variety of mustard was sown on five different dates (29 Sept, 29 Oct, 28 Nov, 28 Dec, 1980 and 27 Jan, 1981). The aphid remained active from 1st week of Nov, 1980 to end Mar, 1981. Maximum aphid population (270/10 cm apical twig) was recorded on crop sown on 28 Nov, 1980. The parasite remained active from 30 Dec to 10 Feb, 6 Jan to 10 Mar, 20 Jan to 17 Mar, 17 Feb to 24 Mar, parasitising 12,5, 19,4, 40.9, 74.0% aphids for Oct, Nov, Dec and Jan sown crops, respectively. The aphid parasitisation was zero for the crop sown on Sept 29, 1980.