Mohammad Akhtar

Roles of organic soil amendments and soil organisms in the biological control of plant-parasitic nematodes: a review.

Organic soil amendments stimulate the activities of microorganisms that are antagonistic to plant-parasitic nematodes. The decomposition of organic matter results in accumulation in the soils of specific compounds that may be nematicidal. Amendments are mainly bio-products and wastes from industrial, agricultural, biological and other activities. Control of plant-parasitic nematodes can be by improvements of soil structure and fertility, alteration of the level of plant-resistance, release of nemato-toxic compounds), parasites (fungi and bacteria) and other nematode antagonistic (biological control agents). The mode of action of organic amendments leading to plant disease control and stimulation of microorganisms is complex and dependent on the nature of the amendments.

Utilization of waste materials in nematode control: A review

Abstract The addition of waste materials from animals and plants to soil has been explored as an alternative means of nematode control. These materials include agricultural wastes in the form of green manures and dried-crop residues in general and industrial by-products, such as oilcakes, sawdust, cellulosic waste, and sugar-cane bagasse in particular. Besides these, other biological wastes (chitin, bone meal, horn meal, sewage-sludge, municipal refuse, and livestock wastes) have been proved succesful in controlling nematodes for several years. The beneficial effects of organic incorporation have been generally considered to be due to direct or indirect stimulation of predators and parasites of plant-parasitic nematodes. Very often, when there was a decrease in the soil-pathogen population, there was a consequent increase in crop yield. This review reveals a promising area of ‘non-conventional’ nematode-management.

Control of plant-parasitic nematodes with organic and inorganic amendments in agricultural soil

Abstract The effects of different application rates of oilcakes of neem ( Azadirachta indica ) and castor ( Ricinus communis ), composted manure and urea on plant-parasitic, predatory and free-living nematodes and growth of pigeonpea ( Cajanus cajan ) in field trials were studied. Amendments to soil with these materials resulted in a significant decrease of plant-parasitic nematodes, whereas predatory and free-living nematodes increased. Neem and castor oilcakes were the most effective in reducing plant-parasitic nematodes. However, amendment to soil of composted manure and urea was found to be beneficial in increasing free-living nematodes. As a consequence of suppression of plant-parasitic nematodes, plant growth parameters improved. Increasing doses of the amendments were found to be effective in further reducing plant-parasitic nematodes and increasing predatory and free-living nematodes.

Potentiality of phytochemicals in nematode control: A review

Abstract In the search for alternatives to chemical control of nematodes and with consideration for resource-poor farmers, the potential nematicidal value of a number of plant parts, by-products, and residues, and plant interculture with other crop plants, have been studied. In order to find out their nematicidal properties, the plant materials have been tested by in-vitro, pot and field trials by extracting or incorporating the materials as soil amendments, seed treatments and/or bare-root dip treatments. Root exudates of certain plants have also exhibited nematicidal activity. However, the mode of action of the materials on nematodes is not understood. The beneficial effects of natural phytochemicals reveals a promising area of non-chemical nematode management, but further work on the plant-based nematicides is needed.

Nematicidal Potential of the Neem Tree Azadirachta indica (A. Juss)

Plant products are receiving greater attention as prophylactics against several species of plant-parasitic nematodes. Numerous experiments have shown the potential nematicidal value of plant parts and their by-products when incorporated into soil or when the plants themselves are interplanted as seedlings among crop plants. Various products (oils, cakes, extracts, etc.) prepared from the leaves and seeds of the neem plant (Azadirachta indica A. Juss) (Family Meliaceae) have been reported as effective protectants against nematode pests when used as root-dips and seed treatments. Nemato-toxic compounds of the neem plant, especially the azadirachtins, are released through volatilization, exudation, leaching and decomposition. The modes of action of these compounds are complex, and a number of mechanisms in relation to nematode management are yet to be fully explored. This review critically assesses the potential of these products in the management of nematodes in tropical agriculture.

Current options in integrated management of plant-parasitic nematodes

Efficient management of plant-parasitic nematodes requires the carefully integrated combination of several methods. Although each individual method of management has a limited use, together, they help in reducing the nematode populations in agricultural soils or in plants. A public desire for methods of managing plant pests in ways that do not pollute or otherwise degrade the environment has increased concomitantly with progress in research. Integrated pest management (IPM) provides a working methodology for pest management in sustainable agriculutural systems. In this paper, current methods for the management of plant-parasitic nematodes are discussed within the guidelines of IPM. The emphasis is on the methods by which decisions are made to manage nematode problems with the most effective and widely used management strategies. The advantages and difficulties associated with nematicidal chemicals (i.e. cost, reinfestation of soil after harvest, contamination of ground water and residues in fruits and vegetables), biological control (by predatory or parasitic fungi and nematodes) and management with cultural methods (including the use of uncontaminated plants or seeds, crop rotation, modification of sowing and/or harvesting times, trap crops and resistant varieties etc.) are considered

Biological control of plant-parasitic nematodes by neem products in agricultural soil

Abstract Various products prepared from neem ( Azadirachta indica ) such as leaf powder, sawdust and oilseed cake, and urea were tested for their activities against plant-parasitic nematodes ( Hoplolaimus indicus , Helicotylenchus indicus , Rotylenchulus reniformis and Meloidogyne incognita juveniles), a predatory nematode ( Dorylaimus elongatus ), free-living nematodes and the growth of chickpea ( Cicer arietinum ) in the field. Soil-amendments with these materials resulted in a significant decrease of plant-parasitic nematodes relative to control plots. In contrast, populations of predatory and free-living nematodes increased. Oilcake was most effective, though all the neem products and urea markedly suppressed plant-parasitic nematodes. However, leaf powder increased populations of predatory and free-living nematodes. All treatments resulted in increased fresh and dry weights and the height and number of pods on chickpea plants.

Effect of crop residues amendments to soil for the control of plant-parasitic nematodes

Abstract Incorporation of harvested crop-residues of marigold, mustard and sunflower into soil proved highly effective in suppressing the incidence of root-knot caused by Meloidogyne incognita and in reducing the population build-up of some plant-parasitic nematodes. Enhanced plant growth of susceptible chilli ( Capsicum annum L.) was directly correlated with the degree of nematode control. Higher dosages resulted in better effects.

Utilisation of plant-origin waste materials for the control of plant-parasitic nematodes

Abstract The nematocidal properties of several waste materials of plant origin were studied in soil infested with plant-parasitic nematodes. Among the materials pressmud, vegetable- and fruit-processing waste and tobacco wastes were the most effective in reducing the incidence of rootknot and development of plant-parasitic nematodes on tomato ( Lycopersicon esculentum Mill.). However, amendments to soil with spent tea, wheat straw, paddy husk, paddy straw, sugarcane trash, domestic garbage, dead vegetation and pigeonpea stubble were also found to be beneficial in nematode control. As a consequence of nematode control plant growth improved, with a few exceptions where higher levels (5% (w/w)) of waste materials were phytoxic.

Effects of two Compositae plant species and two types of fertilizer on nematodes in an alluvial soil, India

Abstract In a field study conducted at Aligarh, India, Compositae plants were used alone and in combination with two types of fertilizers to investigate their effects on the community of soil nematodes. Organic fertilizer (composted manure – an organic source of nitrogen) and synthetic fertilizer (urea – a non-organic source of nitrogen) were incorporated in a field soil at two different dosages. All treatments decreased the number of plant-parasitic nematodes, however, doubling the dosage of fertilizer further decreases nematode numbers. Combination of both fertilizer treatments with Compositae plants were the most effective in suppressing plant-parasitic nematode populations. Both fertilizer types significantly increased number of microbivorous (free-living) nematodes relative to untreated control plots; however, Compositae plant species (Tagetes erecta and Helianthus annuus) did not affect the free-living nematode populations. Populations of predatory nematodes (Mononchus aquaticus and Dorylaimus elongatus) were significantly different in all the treatments. Few differences between the two plant species were found for any of the nematode community measurements.