In vitro toxicity of extracts from Hyptis suaveolens (L.) poit on eggs and second-stage juveniles of Heterodera sacchari

Abstract

The replacement of synthetic nematicides with comparatively more bio-degradable, bio-active plant  extracts is desirable. Studies on the nematicidal potential of different extracts of Hyptis suaveolens on the eggs and second stage juveniles of sugarcane nematode, Heterodera sacchari was conducted. Leaves of H. suaveolens were hydro distilled to extract the essential oil. A second set of the leaves were  extracted separately in dichloromethane (DCM) and in water. Essential oil (EO) obtained was analyzed using Gas chromatography mass spectroscopy (GC/MS). The essential oil was tested in-vitro along with other extracts on the eggs and second stage juveniles of H. sacchari. The fractions were significantly (p<0.05) effective in inducing mortality. Bioactivity was highest at a concentration of 20mg/mL, which was significantly (p<0.05) different from all other concentrations. The essential oil (EO) compared well with the standard carbofuran (CBFN) at 65.58% and 66.06% mortality respectively, while the dichloromethane and aqueous extracts were not as effective. Mortality increased with increase in exposure time. There was total egg hatch inhibition with the essential oil and carbofuran, all the levels of concentration also inhibited egg hatch. The constituent of H. suaveolens as revealed by GC/MS include sabinene (29.5%), betacaryophyllene (11.8%), terpinolene (9.8%) and 1, 8-cineole (7.3%). The extracts of the leaves of H. suaveolens are nematicidal and holds promise as a natural bio-degradable alternative crop protectant against Heterodera sacchari

Key words: Heterodera sacchari, dichloromethane, essential oil,Hyptis suaveolens