Abstract

Four aqueous plant extracts (APEs) of Acorus calamus (L), Xanthium strumarium(L), Polygonum hydropiper (L) and Clerodendron infortunatum (Gaertn) were evaluated under both laboratory and field conditions at 2.5, 5.0 and 10.0% (w/v) concentrations against tea red spider mite, Oligonychus coffeae (Nietner). Also, the impact of APEs on survival and feeding of Stethorus gilvifrons, a potent coccinellid predator of red spider mite was studied. Parameters assessed were ovicidal activity and acaricidal activity in case of red spider mite, and feeding activity and adult mortality for the coccinellid. Strong ovicidal action was observed with X. strumarium (87.09%) and A. calamus (70.62%) whereas least action in P. hydropiper (30.86%) and C. infortunatum (20.58%). All the APEs showed > 50% mortality of red spider mite at higher concentrations (5 and 10%) under laboratory conditions. Field evaluation of APEs recorded 46.9 – 81.8% mite reduction at 5.0% and 64.7 – 100.0% at 10.0% concentration. More acaricidal activity was noticed inC. infortunatum and X. strumarium under field condition. The APEs, even at higher concentration (10%), caused no mortality to the adults of S. gilvifrons for 14 days, and no significant change in feeding after 24 h in comparison with untreated control. Crude plant extracts of A. calamus, X. strumarium, P. hydropiper and C. infortunatum can effectively be utilized as safer phytopesticidal products in both organic and inorganic tea estates as one of the potent tools in integrated mite management.

Key words: Tea, Oligonychus coffeae, aqueous plant extracts, Stethorus gilvifrons.