Bioefficacy assessment of Melia azedarach (L.) seed extract on tea red spider mite, Oligonychus coffeae (Nietner) (Acari: Tetranychidae)

Abstract

Aqueous seed extract of Melia azedarach (L.) was evaluated against tea red spider mite, Oligonychus coffeae (Nietner), in relation to mortality of adult mites, viability of eggs and subsequent adult emergence and oviposition deterrence in the laboratory, and the extract underwent field evaluation in terms of per cent reduction of the mite population. Direct spray methods were used in the laboratory with concentrations of 1%, 2%, 4%, 6%, 8% and 10%. Mortality of O. coffeae was dependent on both concentration and time (56.4% mortality on the first day; 95.6% mortality by the seventh day). The viability of eggs was reduced significantly compared with untreated mite's eggs. Significant reduction in adult emergence and increased duration of total developmental period were noted. Deposition of eggs by adult mites on treated leaf surface was decreased significantly compared with the control. No phytotoxic effect (score 0–5% and grade 1) was observed in the field when tea bushes were sprayed with different doses of aqueous seed extract of M. azedarach. The made tea samples were taint free. An organoleptic test scored both leaf infusions and liquor strength as good, scoring 6.5–7.0 on a 10-point scale. The availability and distribution of this plant (M. azedarach) in and around the tea-growing areas of the sub-Himalayan region, along with its processing for economic utility and inclusion in the current integrated pest management program, is discussed.