Anti-mite activities of Clerodendrum viscosum Ventenat (Verbenaceae) extracts on tea red spider mite, Oligonychus coffeae Nietner (Acarina: Tetranychidae)

Abstract

Acaricidal and ovicidal activities of Clerodendrum viscosum Ventenat (Verbenaceae), a common weed of India, were investigated on tea red spider mite, Oligonychus coffeae Nietner (Acarina: Tetranychidae). Different solvent extracts (water, methanol, acetone and petroleum ether) of C. viscosum at different concentrations (1, 2, 4 and 8%) were used. These solvent extracts exhibited mortality of O. coffeae in the range of 40–90% in water, 67–97% in petroleum ether, 50–80% in acetone and 43–87% in methanol extract. Depending on LC₅₀ values, the relative toxicity was found to be significantly highest against petroleum ether extracts and lowest in water extracts. Acetone extract of C.viscosum recorded maximum ovicidal activity followed by petroleum ether, methanol and the less by water extracts. In the field trials, mite population were significantly lower (P < 0.05) on plots sprayed with different of C. viscosum extracts than the control and at par with chemical acaricide and neem biopesticide. No phytotoxic effect (score, 0–5% and grade 1) was observed in the field from tea bushes sprayed with different doses of extracts of C. viscosum. Made tea samples were taint free. Organoleptic test revealed leaf infusions and liquor strength as good, scoring 6.5–7.0 on a 10-point scale. Availability and distribution of this weed (C. viscosum) in and around tea growing areas of sub-Himalayan region, along with its processing for the feasibility of including C.visosum extracts in the current IPM programme are discussed.

Keywords:

• Clerodendrum viscosum
• Oligonychus coffeae
• acaricide
• ovicide