BIOEFFICACY OF COCCINELLID PREDATORS ON MAJOR TEA PESTS

Abstract

ABSTRACT Twenty species of coccinellid predators were observed in Sub-Himalayan tea plantation of North Bengal during 2004 to 2006. Of these, Micraspis discolor (F) was dominant (42.5%) in the conventionally managed tea plantations. The abundance of M. discolor populations was positively correlated with the abundance of red spider mites (Oligonychus coffeae Neitner, Acarina: Tetranychidae) (R2 =0.705) and tea aphid (Toxoptera aurantii Boyer de Fons, Homoptera: Aphidae) (R2 = 0.893). Both the pests and their predator (M. discolor) populations showed similar patterns of abundance that reached peaks during January to March. In choice test, the mixed population the grub and adult of M. discolor showed a clear choice for the tea aphid. The life cycle studies also suggested that the tea aphid was the preferred prey for M. discolors, but the predator can survive on red spider mite also. The studies on feeding potential indicated that the grubs of M. discolor consumed on an average 280.30 red spider mites and 188.66 tea aphids during its larval period of development, which were 24.10 + 0.77 and 21.70 + 0.72 days, respectively. The regression between the age of grub and rate of consumption showed that the consumption by the predator at larval stage is highly correlated to its age. An adult predator consumed on an average of 20.32 + 11.79 red spider mites per day and 35.9 + 4.95 tea aphids per day. In both case, male individual consumed significantly less number of aphids as compared to the female.