Management of Root Knot Nematode, Meloidogyne incognita Using Tithonia diversifolia and Tagetes minuta Through a Slow-Release Technique in Tomato

Abstract

Tomato (Solanum lycopersicum) is an economically important crop in Africa produced largely by small-scale farmers. The root-knot nematode (RKN), Meloidogyne incognita (Kofoid and White) Chitwood, causes serious constraints in tomato production. Synthetic nematicides have been used in the management of RKN, however, they have adverse effects on users and the environment. Botanical pesticides are a safer alternative since they contain compounds that act as hatching inhibitors, repellents and nematoxicants. These compounds are constituted in leaves, seeds, flowers and roots and are applied through aqeous extracts, essential oils, powder or pellets derived from various plant parts. The use of plant extracts has been effective, however, more than two applications are done for effective RKN management. This study investigated the use of a filter bag as a slow release technique, to ensure the continuous release of the nematotoxic compounds to enhance the management of M. incognita and minimize the number of applications done. Powder and pellet of Mexican sunflower, Tithonia diversifolia Hemsl. and Mexican marigold, Tagetes minuta L. incorporated in a filter bag made of non-woven interfacing fusible fabric, were used in the management of M. incognita in tomato production. The experiment was laid out in a completely randomized design with a Pre-plant and Post-plant application of ammendments. Tomato seedlings were inoculated with about 1500 freshly hatched second-stage juveniles of M. incognita in both trials. Data collected on the nematode population dynamics, changes in tomato fruit qualities, and yield and root phenols and soil chemical properties. Data was subjected to analysis of variance and means separated using the Tukey Studentized Range Test (P = 0.05). Results of this study showed that pellet and powder from respective plant parts significantly (P = ˂0.001) reduced nematode populations relative to the untreated control but compared favorably to the positive control. The filter bag technique significantly improved the management of M. incognita. Pre-plant application of pellets incorporated in the filter bag resulted in plants that had lower egg mass and gall index and soils with lower juvenile populations. The fruit qualities were significantly improved where higher total soluble solids (4.37), total titratable acidity (0.83) and Vitamin C (18.33) content was recorded. The root phenols, N, P, K and organic carbon levels were higher in soils amended with ammendments incorporated in the filter bag. There was however no significant difference between ammendments in the filter bag and those without. The filter bag technique proved to be better in the pre-plant application relative to the post-plant application. These findings indicate that the filter bag technique averts the need for re-application which could help reduce the operation costs.