Department of Entomology, Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176 062, Himachal Pradesh (India).
The predation potential of the adults of Coccinella septempunctata Linn. and larvae of syrphid, Metasyrphus sp. on three species of aphids, viz, Lipaphis erysimi Kalt., Brevicoryne brassicae Linn. and Myzus persicae Sulzer infesting rapeseed was studied in the mid hill zone of Himachal Pradesh. The adult coccinellid consumed a maximum number of about 72 (L. erysimi), 47 (B. brassicae), and 60 (M. persicae) aphidslday. It took 3.3, 4.1 and 2.8 days to consume 100 apterous individuals of L. erysimi, B. brassicae and M. persicae, respectively. The longevity of adult beetle recorded was 30.2±2.46,34.58±1.16 and 31.72±1.98 days with the total consumption of 1435 ± 12.01, 1021.05±8.16 and 628±3.42 aphids on L erysimi, B. brassicae and M. persicae, respectively. The predator-prey ratio was observed as 1:65, 1:64 and 1:132, respectively in L. erysimi, B. brassicae and M. persicae during 1993–94. The syrphid predator, Metasyrphus sp. consumed 40 (L. erysimi), 44 (B. brassicae) and 52 (M. persicae) per day. The larva of the predator consumed a total of 215.42±15.2, 247.32±16.2 and 416.26±14.28 aphids in the three larval instars and completed its larval period in 23.30±1.89, 19.50±1.72 and 22.50±4.74 days on L. erysimi, B. brassicae and M. persicae, respectively. The syrphid larvae were observed feeding on three aphid species in the month of February. The predator prey ratio of 156 (L. erysimi), 1:79 (B. brassicae), and 156 (M. persicae) was recorded during 1992–93. In 1993–94, it was recorded as 152, 1:49 and 1:42 on L. erysimi, B. brassicae and M. persicae, respectively. This suggests the importance of these predators in effectively regulating the population of three aphid species.
