Acaricidal effects of Tagetes minuta L. (Asteraceae) against Tetranychus truncatus Ehara (Prostigmata: Tetranychidae)

Abstract

ABSTRACT The study evaluated the efficacy of solvent fractions of Mexican marigold, Tagetes minuta against the spider mite, Tetranychus truncatus. The dried and pulverized botanical was subjected to sequential extraction using three solvents viz., hexane, chloroform and water in the increasing order of polarity. Solvent fractions were evaluated for their ovicidal and adulticidal activities against T. truncatus in the laboratory at five different concentrations viz., 0.025, 0.05, 0.1, 0.15 and 0.2 %. Results indicated that only hexane fraction at higher concentrations of 0.15 and 2.0 % exhibited significant ovicidal action, causing 100.00 and 81.33 per cent egg mortality, respectively. However, all the fractions recorded significant adulticidal effect at higher concentrations with hexane fractions at 0.2 and 0.15 % recording significantly higher adult mortality (>90 %), followed by chloroform fraction. The best concentrations of the three solvent fractions identified in the laboratory study were evaluated against T. truncatus on amaranthus, in a pot culture experiment. Fourteen days post treatment, hexane fraction at 0.2 % reduced mite population by 88.78 per cent and was superior to neem oil emulsion at 2% (76.44 % reduction), which was on par with chloroform and aqueous fractions. Results of the study identified Mexican marigold as a potential candidate in mite pest management, which may be further validated through multi-locational field trials.