Use of some plant extracts for management of red spider mite, Oligonychus coffeae (Acarina: Tetranychidae) in tea plantations

Laboratory and field studies were undertaken to establish the efficacy of some selected botanicals in the control of the tea red spider mite, Oligonychus coffeae Nietner, a major pest of tea. Bioassays were performed to evaluate the dose-mortality response of adults and eggs of O. coffeae to aqueous plant extracts. The order of adulticidal toxicity based on LC50 and slope values was Sapindus mukorossi L. > Nyctanthes arbor-tristis L. > Phlogacanthus thyrsiformis Nees. The order of ovicidal activity was reversed and was P. thyrsiformis > N. arbor-tristis > S. mukorossi. In addition, different concentrations of the aqueous extract of these plants exhibited repellent properties against adult mites and also significantly decreased the deposition of eggs by the mites on treated tea leaf surfaces. In field conditions, the extracts significantly reduced O. coffeae populations compared to propargite, a synthetic acaricide. There was no phytotoxic effect and the quality of tea was not adversely affected by the treatments. Further, the plant extracts caused no mortality or decrease in the predation efficacy of the adults and fourth instar larvae of Stethorus aptus Kapur, a natural predator of O. coffeae. Using the procedure adopted in this study, tea growers can easily formulate these low-cost eco-friendly botanicals for O. coffeae management in tea plantations.