Seasonal abundance and mutual interference of <i>Diaeretiella rapae</i> (McIntosh) on <i>Brevicoryne brassicae</i>

Brevicoryne brassicae (Hemiptera: Aphididae), known as cabbage aphid, is cosmopolitan in distribution that infests cruciferous crops such as broccoli, cabbage, cauliflower, and mustard. Brevicoryne brassicae is suppressed by various species of natural enemies, the most important and abundant being Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae). The present study was carried out at Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni Solan, Himachal Pradesh, on the seasonal abundance and mutual interference of the parasitoid, D. rapae during the years 2020-2021. The study showed the peak population of both host (221.36 aphids/plant) and parasitoid (27.28 mummified aphids/plant) with 12.32 per cent parasitization on the 10th Standard Meteorological Week (SMW). On the 14th SMW of 2021, the aphid population was lowest (2.72 aphids/plant) and parasitization by D. rapae was highest (47.05%). The D. rapae when foraged at densities of 2, 4, 6 and 8 parasitoids per 30 and 50 constant host nymphs, the third-instar host nymphs had a higher mutual interference coefficient than fourth instar host nymphs. Therefore, D. rapae can be utilized as an important biocontrol agent in the management programme of a cabbage aphid (B. brassicae).