Relative Abundance of Syrphid Predators of Brevicoryne brassicae (L.) in Cauliflower Seed Crop Ecosystem
DOI:
https://doi.org/10.18311/jbc/1987/15422Keywords:
Cabbage Aphid Brevicoryne brassicae, Syrphids, Relative Abundance.Abstract
Nine species of aphidophagous Syrphids, viz., Scaeva pyrastri (Linn.), Episyrphus balteatus (Deg.), Metasyrphus confrater (Wied.), M. corollae (Fabr.), Betasyrphus serarius (Wied.), Ishiodon scutellaris (Fabr.), Sphaerophoria indiana (Bigot), Melanostoma sp. prob. M. univittatum (Wied.) and Eupeodes (?) latilunulatus (Collins) occurred as predators of Brevicoryne brassicae (Linn.) on cauliflower grown for seed production in the mid-hill regions of Himachal Pradesh during 1982-84.
Syrphid adult activity in the field was noticed as soon as aphids started forming colonies. E. balteatus and S. indiana were more abundant throughout the season. The larval counts, however, showed that M. confrater, was the most abundant species accounting for 30.5 and 25.7 per cent of the total predatory larval population in the two years, respectively, followed closely by E. balleatus, S. pyrastri, and E. latilunulatus. The remaining species occurred in low numbers during March-April. Although one or the other species remained active in the field throughout crop season, syrphid larvae were relatively more abundant during March. The impact of predator populations on B. brassicae build-up is discussed on the basis of predator-prey ratio.