Efficacy of Sweet Orange and Cassava Peel Amendments for the Management of Root-knot Nematodes on Tomato

Aim: To determine efficacy of organic amendments in the management of root-knot nematodes.

Design of the Study: Experiments were arranged in a Complete Randomized Design (CRD) with five treatments replicated five times and Randomized Complete Block Design (RCBD) with 11 treatments replicated four times at the laboratory and field respectively.

Study Place and Duration: The studies were carried out in the Nematology laboratory and research field at the Faculty of Agriculture, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana from March, 2014 to December, 2015.

Methodology: Five aqueous extracts of: 1) Fresh sweet orange peel (FOP), 2) Fresh cassava peel (FCP), 3) Dry sweet orange peel (DOP) and 4) Dry cassava peel (DCP) on egg hatching inhibition and juvenile mortality of root-knot nematodes were studied at the laboratory. Sterilized water was used as the control. Eleven treatments: 1) FOP, 2) DOP, 3) FCP, 4) DCP, 5) FCP+FOP, 6) FOP+FCP, 7) DOP+DCP, 8) DCP+DOP, 9) NPK and ((NH4)2 SO4) fertilizers, 10) Carbofuran and 11) No application (control) against root-knot nematodes were studied on the field.

Results: At the laboratory, the highest percentage egg hatching inhibition (87.8%) and juvenile mortality (94.8%) of root-knot nematodes were recorded in the FOP aqueous extract. Significant differences (P<0.05) were observed between FOP aqueous extract and the rest of the treatments in the mortality of root-knot nematodes. For the field experiment, combined application of FOP and FCP significantly increased (P<0.05) yield more than the rest of the treatments. Carbofuran, followed by the combined application of FOP and FCP significantly reduced (P<0.05) gall index, number of eggs, number of root-knot nematode juveniles in the root and the soil in both seasons. However, no significant difference (P>0.05) was observed between carbofuran and combined application of FOP and FCP.

Conclusion: The sweet orange and cassava peels were found to be effective in reducing galling and population of root-knot nematodes in the roots and soil of tomato. Also, the aqueous extracts of FOP, DOP and FCP showed high potential in egg hatching inhibition and juvenile mortality of root-knot nematodes. Further evaluation of the combined application of FOP and FCP at farmers’ fields is recommended. Also, methods of application, for example, in the form of aqueous extract should be tested.