A study was conducted to assess the functional response of different life stages of the predacious coccinellid, Adalia tetraspilota (Hope) feeding on various densities of cabbage aphid, Brevicoryne brassicae (L.) under controlled conditions. It revealed that all stages of A. tetraspilota exhibit Type II functional response curve (a curvilinear rise to plateau) as B. brassicae densities increase and the curve predicted by Holling's disk equation did not differ significantly from the observed functional response curve. The fourth instar larva consumed more aphids (28.40 aphids / day) followed by adult female (25.06 aphids / day), third instar larva (24.06 aphids / day), second instar larva (21.73 aphids/ day), adult male (20.06 aphids/day) and first instar (13.06 aphid /day). The maximum search rate with shortest handling time was recorded for fourth instar larva (0.6383) followed by adult female (0.6264). The results suggest that the fourth instar larva are best suited for field releases for the management of B. brassicae. However, further field experiments are needed for confirming its potential.
Keywords
Adalia tetraspilota, Aphididae, Brevicoryne brassicae, Coccinellidae, Functional Response, Handling Time, Predation and Search Rates.
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