Thesis Abstract

Abstract
Root-knot nematodes (Meloidogyne javanica Treub) are a major threat to tomato (Solanum lycopersicum Mill) production worldwide. In this study, the effects of botanicals, soil amendments, and polyethylene mulch colors on root-knot nematode infection in tomato plants were investigated. The experiment was conducted in a randomized complete block design with three replications. The treatments included botanical extracts of neem (Azadirachta indica), marigold (Tagetes erecta), and garlic (Allium sativum), soil amendments such as biochar and compost, and polyethylene mulch colors of black, silver, and white. Results indicated that all botanical extracts showed significant nematicidal effects against Meloidogyne javanica compared to the untreated control. Among the botanicals, neem extract exhibited the highest efficacy in reducing nematode infection in tomato roots. Soil amendments of biochar and compost also demonstrated promising results in reducing nematode populations in the soil and improving plant growth parameters. Biochar, in particular, showed significant suppression of nematode infection and enhanced plant growth. Furthermore, the color of polyethylene mulch had a significant impact on nematode infection levels. The black polyethylene mulch was found to be the most effective in reducing nematode penetration into tomato roots compared to silver and white mulches. This effect could be attributed to the ability of black mulch to raise soil temperatures, which may have detrimental effects on nematode survival and mobility. Overall, the combined application of neem botanical extract, biochar soil amendment, and black polyethylene mulch showed the most effective suppression of Meloidogyne javanica infection in tomato plants. These results suggest that an integrated approach utilizing botanicals, soil amendments, and mulch color selection can be an effective strategy for managing root-knot nematodes in tomato production systems. Further research is warranted to explore the underlying mechanisms of these treatments and their long-term effects on soil health and crop productivity.

Thesis Overview

    Tomato (Solanum lycopersicum Mill) is a solanacious plant. The fruit is very rich in essential vitamins and mineral salts (Peet,2001). It generates income to its growers. It is tropical warm season crop, said to have originated in tropical Central and South America(COPR,1983), and it is grown all over Nigeria. The bulk of production is from the dry season cropping particularly under irrigation in the Northern states and near riverbanks in the southern states of Nigeria. According to COPR(1983),the total land area covered annually is over one million hectares with most of the production from the Northern Guinea Sudan Savannah. The area of land used for tomato production in tropical Africa is about 300,000 hectares with an estimated annual production of 2.3 million tonnes. Nigeria is the largest producer with 126,000 hectares and annual production of about 879,000 tonnes ( Van der Vassen et al.,2004). The average yields in local farms range from 5 to 10 t/ha, while 30 t/ha have been recorded in research farms ( Adeyemi, 2010).

    Uguru (1996) stated that tomato is a short –lived herbaceous annual with weak trailing much branched stem with hairs at juvenile stage of development. Tomato is a warm season crop that grows well in areas with evenly distributed rain fall and with long period of sunshine. Fruits of local varieties in Nigeria are thin-walled, heavily seeded and sour in taste. Tomato fruits contain high level of vitamins A, B, and C (Erince, 1999). Purseglove (1998) reported that tomatoes were used in large quantities to produce sauce, ketchup, puree and juice. Green tomatoes are used for pickles and the seeds are extracted from the pulp are used in canning industry. Tomato is one of the most important vegetables grown for edible fruits consumption in virtually every home in Nigeria. Its production in South Western Nigeria is concentrated mainly during the hot raining season (Ahmad and Singh, 2005). According to Adelana (1976), tomato is usually grown in Southern part of Nigeria in small holdings in farms and gardens under rainfed conditions while it is grown in the Northern States under irrigation.

            Tomato grows well in many types of soils ranging from sandy to the heavy clayey soils (Uguru,1996). Well drained, fertile soils, with good moisture retaining capacity and high level of organic manures are required for the production of tomato ( Tindal, 1998).  Soil is generally a favourable habitat for the proliferation of saprophytic and pathogenic micro-organisms, such as viruses, bacteria, fungi, algae and protozoa (Atlas and Bartha,1993). Soil also supports plant life by providing nutrients and mechanical support. It is one of the vast dynamic sites for biological interactions in nature. Many biochemical reactions which result in distribution of organic matter and nutrients normally occur in the soil.  Jaraba et al.,(2007) reported that sand to sandy-loam soils are conducive to  Meloidogyne species .

    The production of tomato is limited by the attack of pest and diseases. This results in acute shortage of the fresh fruits in certain periods of the year. Yield losses are partly attributed to the susceptibility of tomato cultivars to serious pests and diseases (Udo, 2004). More than a hundred different pest species have been recorded worldwide on tomato crops(Peet,2001; Udo,2004). They include nematodes, mites, thrips, aphids, moths, whiteflies, beetles and flies (COPR, 1983; Kessel,2003).

        Nematodes are one of the major pests of tomato globally especially in the tropical and subtropical regions.  The production of tomato is impaired by among other factors its infections by nematodes (Abubakar et al., 2004). Adesiyan et al.,(1990) reported reductions in yield ranging from 28 to 68%. Over sixty species of plant parasitic nematode attack tomato but the most destructive nematodes responsible for enormous yield losses of tomato are the root-knot nematodes belonging to the genus, Meloidogyne (Sasser 1989. Dufour et al.,., 2003; Udo, 2004).

 Udo (2004) stated that about 29-50% overall yield reduction of tomato in the tropics is attributed to the root-knot nematodes. Root knot nematodes (Meloidogyne spp.) are small microscopic roundworm organisms grouped as a major pathogen of vegetable crops throughout the world, affecting the quantity and quality of marketable yields     (Kingland, 2001). They infect plant roots by producing galls through their feeding habits (Nesmith, 2000). These nematodes are responsible for a greater yield loss of tomatoes when they infest plants at the seedling stage (Vavring, 1991; Mullins, 2000; Dufour et al., 2003). According to Adesiyan et al., (1990), nematodes can predispose plants to infections, break disease resistance, act synergistically in the development of the disease or are vectors of the disease organisms.

        Nematodes in agricultural soils have been controlled using such measures as chemicals like furadan, sincocin and oxamyl which are very expensive and misapplication might result in an adverse effect on the environment. Pyrethriods and other newly developed safer pesticides are expensive. Other control measures like use of biological agents (Verticillium chlamydosporium and Arthrobotrys oligospora), resistant varieties, botanicals, organic manures, crop rotation and time of planting are also employed in controlling plant pathogenic nematodes in the soil. Atungwu (2006) reported that several organic materials have been effectively used for the management of nematode pests of crops throughout the world. Atungwu et al., (2010) stated that although chemical control gives instant reduction of nematodes, its expensive cost forces farmers to exploit indigenous control methods.  Other alternative control measures which are cheaper, available and environmentally friendly should therefore be developed and used in controlling nematode attacks on tomato to ensure higher productivity and sustenance of the crop. The objectives of this research are therefore to:

1. evaluate the efficacy of some aqueous leaf extracts in controlling root-knot nematode infections on tomato.
2. evaluate the effect of different soil amendments in controlling root-knot nematode infections on tomato.
3. evaluate the effect of different coloured polyethylene mulches in controlling root-knot nematode infections on tomato.