Potential ofNyctanthes arbor-tristisL.,Phlogacanthus thyrsiformisNees andSapindus mukorossiL. as novel acaricides of natural origin

Abstract

Aqueous extract of three indigenous medicinal plants viz., Nyctanthes arbor-tristis L. (Oleaceae), Phlogacanthus thyrsiformis Nees (Acanthaceae) and Sapindus mukorossi L. (Sapindaceae) was evaluated in the laboratory against the tea red spider mite, Oligonychus coffeae Nietner (Tetranychidae) to determine its effect on adult mortality, viability of eggs, oviposition deterrence and repellent properties. The direct spray method was used in the laboratory at concentrations of 2, 4, 6 and 8 g/l. Mortality of O. coffeae was dependent on both concentration and time after application. Deposition of eggs by adult mites on treated leaf surfaces decreased significantly and the viability of eggs was also significantly reduced. In addition, different concentrations of the aqueous extract of these chosen plants also exhibited repellent properties against adult mites. Among the chosen plant extracts, S. mukorossi registered highest mortality in both adults and egg forms, whereas P. thyrsiformis showed significantly higher repellence property against O. coffeae. The plant extracts caused no mortality to the adults and 4th instar larvae of Stethorus aptus, a natural predator of O. coffeae and no significant change in predatory efficiency was recorded in comparison with untreated control. Availability and distribution of these plants in and around tea growing areas of Assam, along with the feasibility of processing, may be thus included in the current IPM programme in tea.