Evaluation of sweet orange peel aqueous extract as root knot nematode suppressant

Abstract

The toxic effect of the aqueous extract of sweet orange (Citrus sinensis) to the root knot nematode, Meloidogyne incognita, was compared to that of carbofuran (a synthetic nematicide) in the laboratory and in the field during the 2007 and 2008 planting season at Ahmadu Bello University, College ofAgriculture, Kabba. The laboratory experiment tested the effect of citrus peel extract and carbofuran on egg hatch and juvenile mortality of the nematode while the field experiment tested the effect of the treatments on soil and tomato root populations of the nematode. Sweet orange peel aqueous extract was applied at 0, 25, 50, 75 and 100% concentrations, while carbofuran was applied at 0, 250, 500, 750 and 1000ppm on the field and in the laboratory on egg hatch inhibition and juvenile mortality of M. incognita. The experiment lasted for a period of six months on the field and seven days in the laboratory for each year. The results from the field experiment showed that citrus peel aqueous extract and carbofuran solution brought about significant reduction in nematode
multiplication rate and consequent root damage (root gall index) as compared with the untreated control. The higher concentrations (750 and 1000ppm) of sweet orange peel aqueous extract were significantly more effective than lower concentrations of 250 and 500ppm in suppressing nematode population in the soil and root. In the laboratory, citrus peel extract and carbofuran inhibited Meloidogyne incognita egg hatch and juvenile survival. The result indicates with respect to all the tested parameters that sweet orange peel aqueous extract is toxic to root-knot nematode and can be incorporated into its control system and as potential raw material for manufacturing organic based nematicide.