Utilization of Organic Wastes for the Management of Phyto-Parasitic Nematodes in Developing Economies

The agricultural system in Nigeria and most developing countries has been dominated by the use of inorganic fertilizers as nutrient sources and synthetic pesticides for the management of pests and diseases. However the prices of these agro-chemicals have been skyrocketing beyond the reach of the rural poor farmer. Associated with this is their availability which is very highly unpredictable, thereby exposing the farmers to undue hardships in the crop production chain. Due to the high prices and unpredictable nature of the availability of these inputs, the rural poor farmers have resorted to utilizing organic materials /wastes principally as nutrient sources. These wastes however, have been shown to control a number of pests and diseases.


Introduction
The agricultural system in Nigeria and most developing countries has been dominated by the use of inorganic fertilizers as nutrient sources and synthetic pesticides for the management of pests and diseases.However the prices of these agro-chemicals have been skyrocketing beyond the reach of the rural poor farmer.Associated with this is their availability which is very highly unpredictable, thereby exposing the farmers to undue hardships in the crop production chain.Due to the high prices and unpredictable nature of the availability of these inputs, the rural poor farmers have resorted to utilizing organic materials /wastes principally as nutrient sources.These wastes however, have been shown to control a number of pests and diseases.
The term' waste' can be loosely defined as any material that is no longer of use, useless, of no further use to the owner and is, hence discarded or unwanted after use or a manufacturing process.These materials include agricultural wastes in the form of farm yard manure and dry-crop residues, sewage sludge, municipal refuse, industrial byproducts, such as oilcakes, sawdust and cellulosic waste.Others are animal wastes such as feathers, bone meal, horn meal, and livestock wastes.Most discarded wastes, however, can be reused or recycled.This is the basis of the rag picking trade, the rifting through refuse dumps for recovery and resale of some materials.Today, heaps of refuse dump sites are disappearing in Nigeria because farmers evacuate them for use on their farms as organic fertilizers.Fortunately, these have been found to control phyto-parasitic nematodes among other diseases (Abubakar and Adamu, 2004;Abubakar and Majeed, 2000;Akhtar and Alam, 1993;Chindo and Khan, 1990;Hassan et al., 2010).This is becoming an unconscious but well organized economically important waste management practice in Nigeria and many West African countries with attendant environmental benefits.
In recent years, there has been tremendous increase in public awareness on environmental pollution and climate change associated with pesticide toxicity and residues.This resulted in the shift in pest control strategies from chemical to the environmental era in the late 1980s.Since then several workers have reported that waste materials either of animal, plant or industrial origin have nematicidal and plant growth promoting properties (Akhtar and Alam, 1993;Chindo & Khan, 1990;Kimpinski et al., 2003.This has been exploited as an alternative means of nematode control (Abubakar and Adamu, 2004;Abubakar and Majeed, 2000;Hassan et al., 2010;Nico et al., 2004;Nwanguma and Awoderu, 2002;).The beneficial effects of organic incorporation have been generally considered to be due to increase in soil nutrients, improvement in soil physical and chemical properties (Huang and Huang, 1993;Hungalle, et al., 1986;Kang et al, 1981), direct or indirect stimulation of predators and parasites of phyto-parasitic nematodes (Kumar, 2007;Kumar et al, 2005;Kumar and Singh, 2011), and release of chemicals that act as nematicides (Akhtar and Alam, 1993;Sukul, 1992).Very often, when there was a decrease in the soil-pathogen population, there was a consequent increase in crop yield.(Akhtar, 1993;Akhtar and Alam 1993;Chindo and Khan, 1990).
Given the high cost and unpredictable supply of inorganic fertilizers and synthetic nematicdes, the best way to overcome such condition in the developing economies is to utilize waste resources for sustainable crop production and plant disease management.Given the importance of organic wastes highlighted above, this chapter intends to: i. put together the research works published on the utilization of organic wastes for the management of plant disease with special reference to phyto-parasitic nematodes, ii.examine the prospects of their usage in modern day agriculture, iii.look at the challenges posed in the utilization of these wastes particularly in large scale agriculture, and iv.attempt to proffer suggestions towards addressing these challenges.

Deployment of organic wastes for the management of phyto-parasitic nematodes
The food and agricultural organization (FAO) of the United Nations defines sustainable agriculture as a practice that involves the successful management of resources for agriculture to satisfy human needs while, maintaining or enhancing the quality of the environment and conserving natural resources (FAO, 1989).The system does not unduly deplete the resource as it makes best use of energy and materials, ensure good and reliable yields, and benefit the health and wealth of the local population at competitive production costs (Wood, 1996).Organic wastes perfectly fit into this definition.Being products of crop farms, domestic use, animal or industrial wastes, they are often recycled from the soil to farm produce thereby ensuring conservation of resources and environmental cleanliness.In addition, indirect benefits of pest and disease management are achieved.Numerous examples of these benefits on the management of phyto-parasitic nematodes have been reported by several workers.

Wastes from plants and plant origin
Compost made of agricultural and industrial wastes have been widely used as amendment in soil for the management of soil-borne diseases (Hoitink and Boehm, 1999;Shiau et. al., 1999).In particular, several authors have reported suppression of diseases caused by root-knot nematodes with composted agricultural wastes (McSorely and Gallaher, 1995;Oka and Yerumiyahu, 2002).McSorely and Gallaher (1996) reported reductions in populations of the nematodes Paratrichodorus minor, M.incognita, Criconemella spp and Pratylenchus spp following applications of yard waste compost on maize (Zea mays) in Florida, USA.Forage yield of maize was increased by 10 to 212% when compared with the control.
In Spain, Andres, et al. (2004) using different composted materials at different rates in potting mixtures for the management of Meloidogyne species, found that root galling and final nematode populations of M. incognita race1 and M. javanica in tomato and olive plants were reduced.Increasing the rate of the test materials exponentially reduced galling and final population density of M.incognita by 40.8 and 81.9%, respectively (Table 1).Similar results were obtained for M. javanica.In south western Nigeria, Olabiyi et al. (2007) found that both decomposed and un-decomposed manure applied as organic amendment caused significant reduction in the soil population of Meloidogyne spp.Helicotylenchus sp. and Xiphinema sp. on cowpea.The organic manure resulted in a significant reduction of root galls on the cowpea (Table 2).
Table 1.Effects of composited amendments of potting mixtures on the root galling and finl population of Meloidogyne incognita race I and M. javanica on tomato and olive planting stock.
Table 2. Soil Nematode Population in 200 ml soil sample at planting (initial population) and harvest (final population), percentage reduction of nematodes and root gall index.

Use of plant parts
Numerous plant parts used as organic amendments have been shown to control phytoparasitic nematodes.Neem (Azadirachta indica) is the best known example that act by releasing pre-formed nematicidal constituents into soil.Neem products, including leaf, seed kernel, seed powders, seed extracts, oil, saw dust and particularly oil cake, have been reported as effective for the control of several nematode species (Egunjobi andAfolami, 1976, Akhtar, 1998 ).Neem constituents, such as nimbin, salanin, thionemone, azadirachtin and various flavonoids, have nematidal effects; triterpene compounds in neem oil cake inhibit the nitrification process and increase available nitrogen for the same amount of fertilizer (Akhtar and Alam, 1993).Akhtar (1998) reported the effect of two neem-based granular products, Achook and Sunneem G, urea and compost manure incorporated in the soil.These treatments were found to decrease the number of phyto-parasitic nematodes with increasing doses of plant products.Combination of both neem with urea were reported to be the most effective in suppressing this pathogen.

Use of animal and industrial wastes
Several animal and industrial wastes have been found to be very efficacious in the management of phyto-parasitic nematodes when applied to the soil.For instance steer and chicken manures reduced number of cyst and citrus nematodes and resulted in increased yields of potato and citrus (Gonzalez and Canto-Saenz, 1993).Chindo and Khan (1990) reported a significant reduction of root-knot nematode populations and root gall index following application of poultry manure on tomato (Table 3).Hassan et al. (2010) reported the use of refuse dump (RD), saw dust (SD) and rice husk (RH) for nematode control with attendant increases in crop yield in tomato in northern Nigeria.Table 3.Effect of soil amendment with four levels of poultry manure on the development of M. incognita and growth of tomato cv.Enterpriser in the greenhouse.
Refuse dump was found to perform best compared to rice husk (RH) and sawdust (SD) and this was attributed to the lower C: N ratio of the RD compared to SD and RH (Table 4&5).
Table 4. Effect of soil amendment with three organic wastes on the number of galls, egg masses and populations of Meloidogyne spp. on tomato in the villages of Arewaci and Kurmi Bomo of Zaria, Nigeria This is in conformity with the report of Miller et al., (1973) that availability of more nitrogen enhances the ability of the organic amendment to control nematodes.Similar achievements of nematode control through the use of several organic amendments have been reported by other workers (Abubakar and Adamu, 2004;Abubakar and Majeed, 2000;Khan and Shaukat 2002;Nwanguma and Awoderu, 2002;Nico et al., 2004).The abundance of refuse dump, industrial sawdust and rice husk all over Nigeria and most developing countries makes them very suitable candidates for deployment as soil organic amendments for the management of phyto-parasitic nematodes.
Source; Hassan, et. al., 2010 Table 5.Effect of soil amendment with three organic wastes on the yield and growth of tomato in the villages of Arewaci and Kurmi Bomo of Zaria, Nigeria The beneficial effects of organic wastes are both direct and indirect.They affect the nematodes directly by releasing toxic products (after decomposition) that kill or inactivate the nematodes (Bello et al., 2006).They indirectly control nematode effects by increasing soil fertility to the advantage of the crop (Boehm et al., 1993).In addition to soil fertility, soil amendment with organic matter may also alter soil physical and chemical properties, and thereby affecting soil microflora (Huang and Huang, 1993).
Nematodes are important participants in the underground energy transfer system.They consume living plant material, fungi, bacteria, mites, insects and each other and are themselves consumed in turn.Some fungi do capture nematodes with traps, sticky knobs and other specialized structures (Dropkin, 1980;Jaffe et al., 1998;Kumar et al., 2011)

(Table 6 &7).
There is substantial evidence that the addition of organic matter in the form of compost or manure will decrease nematode populations and associated damage to crops (Akhtar and Alam, 1993;Oka and Yerumiyahu, 2002;Stirling and Smith, 1991;Walker, 2004).
The fungus, Arthrobotrys species is a nematode-trapping fungus, which produces constricting rings for capturing and killing nematodes.The biocontrol efficiency of this fungus in reducing the population of Meliodogyne javanica was described by Galper et al. (1995).However, excellent control of root knot nematodes of vegetables following the application of granular formulations of A. dactyloides in pot and field was obtained by Sterling et al. (1998) and Sterling and Smith (1998).Hoffmann -Hergarten and Sikora (1993) also reported that the efficacy of A. dactyloides and some other Arthrobotrys spp. was enhanced with mustard as green manure and barley straw as soil amendment against early penetration of rape roots by Heterodera schachtii.Kumar and Singh (2005) reported that A. dactyloides with cow dung manure reduced infection of plants for 10 weeks due to well developed roots that protected the initial stage of infection by capturing and killing of nematodes by this fungus.These findings are in consonance with similar reports by Sterling et al., (1998), and Stirling and Smith (1998) where formulation of A. dactyloides caused 57 -96% reduction in number of root-knots and 75-80% reduction in number of nematodes per plant in tomato in pot and field experiments, respectively.
Source; Kumar et.al., 2011 Table 6.In vitro trapping of plant parasitic nematodes by direct formed rings of five isolates of Dactylaria brochopaga after 12 h of inoculation.
Generally, refuse dump, composts and some industrial wastes are abundant all over the major cities in the developing world.With support from governments and some private organizations, the abundance of these wastes can be channeled into our agricultural systems for the management of plant parasitic nematodes and other plant diseases.

Deployment of allelopatic plants in the management of phyto-parasitic nematodes
Production of allelopathic chemicals that function as nematode antagonistic compounds has been demonstrated in many plants such as castor bean, chrysanthemum, velvet bean, sesame, jack bean, crotalaria, sorghum-sudan, indigo, tephrosia, neem, Tamarindus indica, flame of the forest.These chemicals include saponins, tannins, polythienyls, glucosiniolates, cyanogenic glucosides, alkaloids, lipids, terpenoids, triterpenoids and phenolics, among others.When grown as allelopathic cover crops, bioactive compounds are exuded during the growing season or released during green manure decomposition.Sunn hemp, a typical legume, and sorghum-Sudan, a prolific grass plant grown for its biomass, are popular nematode-suppressive cover crops that produce the allelochemicals known as monocrotaline and dhurrin, respectively (Chitwood, 2002, Grossman, 1988, Hackney and Dickerson, 1975. Ball-Coelho et al., 2003) found that using forage pearl millet (Canadian Hybrid 101) and marigold (rakerjack) as rotation crops with potatoes resulted in fewer root lesion nematodes and increased potato yield than rotation with rye.

Deployment of plant extracts in the management of phyto-parasitic nematodes
The use of plant extracts is one of the promising tools being investigated for the management of nematode diseases.They are relatively cheap, easy to apply, with minimal environmental hazards and have the capacity to structurally and nutritionally improve the soil health.Several parts of neem tree and their extracts are known to exhibit nematicidal activities (Bello et al., 2006((Fig.1&2), Mojundar, 1995, Raguraman et. al., 2004, Suresh et al., 2004), and many neem based pesticidal formulations have been developed and marketed.The extracts of five organic waste of citrus (cv.Late Valencia), cocoa bean testa, rice husk, poultry manure and oil palm bunch were reported to have inhibitory effect in the egg masses of M. incognita (Osei et al., 2011).Adegbite and Adesiyan (2005) reported that the root extracts of Siam weed, neem, lemon grass and castor bean were found to have nematicidal properties.Rakesh et al. (2000) determined the efficacy of essential oils in Cymbopogon martinii, Mentha aivensis and Ociumum basilicum on the production potential of root-knot nematode, M. incognita and growth of black henbane, Hyoscyamus niger.Reduction of population of M.incognita by all the oils was achieved.The effect of aqueous leaf extracts of seven plants species on hatching and mortality of second stage juneniles of M. incognita were tested.There was a great reduction in hatching and an increase in nematode mortality with Murraya koenigii (curry leaf), Jasminum sambac (Jasmine), Citrus aurantifolis (sour orange), Zizyphus jujuba (ber), Hibiscus rarasieusis (China rose), and Justicia gandurosa (J.gendaussa) leaf extracts (Padhi et al., 2000).Bello et al. (2006) and Bello (2010) reported mortality of M. incognita following the use of water extracts of A. indica, Tamarmdus indica, Cassia sieberiana, Cassia siamea, and Delonix regia Bharadwaj and Sharma (2007) observed that higher concentration levels of Carica papaya inhibited hatching of M. incognita.Similarly.The plant extract of stored pulpified peels of lemon, orange and grape fruit demonstrated significant nematicidal activity against M. incognita second stage juveniles after 48 hours of exposure (Tsai, 2008).Also, root exudates of Gaillardia pulchella were reported to be lethal to J2 of M. incognita and inhibitory to egg hatch at the concentration of 250 ppm or higher (Tsay, et al., 2004).
Chemical based conventional systems of agricultural production have created many sources of pollution that either directly or in indirectly contribute to degradation of the environment and destruction of our natural resource -base.In this situation organic waste could be utilized both for the control of plant parasitic nematodes and other plants pathogenic diseases and improvement of soils and maintenance of a productive environment.For sustainability of agriculture in the developing economies, farmers should divorce themselves from the synthetic pesticides strategy for phyto-parasitic nematode management and marry the phytochemical option which is non-toxic to man and its environment.Most of these plants are richly available, biodegradable and affordable to the peasant farmers in the developing world.

Challenges and prospects in the utilization of organic wastes for the management of phyto-parasitic nematodes
The deployment of organic materials for the management of phyto-parasitic nematodes in modern day agriculture is pregnant with several challenges.These include among others initial fear of the unknown, dosage labour requirement and financial constraints

Fear of the unknown
The adoption of any new farming technology is often received by farmers with a lot of skeptism because of fear of the implications of the new technology on the productivity of their crops.Thus, adoption of such technologies is often slow until when fully convinced of its advantages over the traditional systems.Experience has shown that the transition from conventional agriculture to nature farming or organic farming can involve certain risks, such as initial lower yields and increased pest problems (James, 1994).However, once the transition period is over, which might take several years, most farmers find their new farming systems to be stable, productive, manageable, and profitable.In this case, the use of organic wastes will be beneficial through abundance of beneficial micro-organisms (characteristic of organically amended soils) which can fix atmospheric nitrogen, decompose organic wastes and residues, detoxify pesticides, suppress plant diseases and soil-borne pathogens, enhance nutrient cycling and produce bioactive compounds such as vitamins hormones and enzymes that stimulate plant growth (Higa, 1995).Besides, amendments may increase soil populations of micro-organisms antagonistic to nematodes, but are also known to release several toxic compounds during their decomposition in soil that act directly by poisoning the phyto-parasitic nematodes (Oka and Pivonia, 2002).

Dosage/Application rate
The quantities of organic wastes usually required per unit area are large.This poses problems of acquisition transportation and application particularly in large scale farms.Fortunately, in Nigeria and other developing countries, these wastes are in abundance.Large quantities of refuse dump sites, rice and other cereal straws, industrial wastes such as saw dust, rice husk, by-products of breweries, agro-processing plants etc abound.Concerted efforts by governments, organizations, non-governmental organizations (NGOs), research centers etc. are needed to mobilize these resources for use either directly or transformed into other products that can be utilized more easily by the farmers.In Taiwan for instance, fertilizers and organic wastes have been transformed into different products that are used to control plant diseases including nematodes (Huang and Huang, 1993;Huang and Kuhlman, 1991;Huang et al., 2003).

Labor requirement
Traditionally organic farming is labor and knowledge -intensive whereas conventional farming is capital intensive, requiring more energy and manufactured inputs (Halberg, 2006).This, however, is not a serious drawback in most developing economies .There is abundance of idle labour which can be readily deployed to the movement and application of these wastes to work in farms thereby mitigating the myriad of social ills that is often associated with such idle minds.

Financial constraints
Research and development in organic farming is normally constrained by scarce funding from government and large commercial stakeholders, and smaller commercial players are generally unable to allocate funds for research and development.In order to have a breakthrough, research organizations such as the Colloquium of Organic Research in the United Kingdom (UK) and the Scientific Committee for Organic Agriculture Research in the USA should be formed in the developing countries such as Nigeria to boost agriculture and provide employment for the increasing population.
Organic agriculture in developing economy can be improved upon with adequate funding, removal of production subsidies that have adverse economic, social and environmental effects, investment in agricultural science and technology that can sustain the necessary increase of food supply without harmful tradeoffs involving excessive use of water, nutrients or pesticides.

Conclussion
In view of the foregoing, it is clear that synthetic pesticide-based conventional system of agricultural production which has created many sources of pollution either directly or indirectly, contributed to degradation of the environment and destruction of our natural resource needs to be critically examined.This is with the view to minimizing usage of these compounds and deploying much more effective, cost effective and environmentally friendly strategies that will ensure good health of our people and enhance the stability of our agricultural soils.An area that appears to hold the greatest promise for technological advances in crop production, crop protection and natural resource conservation is that of organic wastes and organic materials.The generation of solid waste has been increasing steadily after the past ten years due to rising population, urbanization and industrialization in Nigeria and most developing countries.In the early 1970s, prior to the discovery of oil in Nigeria, municipal wastes were managed as compost manure and used as organic amendments.The onset of oil wealth changed lifestyle patterns leading to increased generation of varied components of municipal solid wastes which can be channeled towards improvement in crop production.