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Summaries of presentations

Dr F. Lamberti (Italy) addressed the meeting on Nematology in developing countries: problems and progress and indicated that root-knot nematodes are major pests of various crops in developing countries. Other important plant-parasitic nematodes are species of cyst nematodes, Aphelenchoides besseyi, Ditylenchus dipsaci and D. angustus, species of Pratylenchus and Hirschmanniella, Radopholus similis, Rotylenchulus reniformis, species of Hoplolaimus and Xiphinema ifacolum. He added that these nematodes can be controlled by various methods but nematicides are generally not applied because of being too expensive. Rotations are time-consuming and not applicable to polyphagous species on cash crops. Biological control is not yet practical. Soil solarization is a feasible technique in areas with hot summers, provided that plastic for mulching and water for irrigation are available.

Dr Lamberti concluded that the main constraint to the development of applied nematology in developing countries is the lack of an interaction between researchers, plant protection officers and farmers. Extension service is poor and very little information is known on the real problems because they do not have the facilities and/or the habit of going into the field. Even if some good research is done or practical results are obtained these are not transferred to users and remain confined to laboratories or to some scientific journals.

Dr M.R. Siddiqi (United Kingdom), in the presentation on Techniques and methodologies for nematode disease diagnosis and nematode identification, stated that nematode disease detection and species identification are basic to any control strategy. The field symptoms on above-ground and underground plant parts produced by ecto- and endoparasitic nematodes were discussed. Methods of surveying, collecting, killing, fixing and mounting nematodes were detailed. Taxonomy and species concepts were briefly discussed. Morpho-anatomical characters of the phenotype are most important in nematode identification. Biological data and biochemical and cytogenetic characters are also important, especially in the identification of host-specific and endoparasitic nematodes. Use of computers in recording, retrieving and analysing survey and identification data was discussed and it was suggested that national and international data should be exchanged by interlinking and networking. Importance of nematode taxonomic expertise, nematode reference collection, identification equipment and literature was emphasized. Need for having good diagnostic centres was highlighted.

Dr D.L. Trudgill (United Kingdom) presented a paper on Nematode population dynamics, threshold levels and estimation of crop losses. He indicated that both yield loss and population dynamics are influenced by initial population density (Pi), by host factors such as susceptibility and tolerance, and by environmental factors such as soil type, planting time, fertilizer and water availability. Equations exist which can be used to model yield losses and population dynamics, but these equations are not predictive because the yield losses caused by nematodes are given as a proportion of the nematode-free yield. Because of this, and because of the various interactions and the complexity of the economics involved, for most nematode/crop combinations the development of economic thresholds is a distant goal. What is required is better information on the relationship between nematode numbers and crop yields. To achieve this field trials are needed at sites where nematode numbers have been manipulated to give a range of Pis. There are several ways of conducting such trials, all of which have their limitations and involve considerable effort to minimize variation. Other difficulties, especially for Meloidogyne spp., are how and when to measure Pi. That such problems are still unresolved points to the relatively undeveloped state of our knowledge. Knowledge is also required for a better understanding of how differences in tolerance of damage and in host status between crops and cultivars affect nematode multiplication rates. Although nematology is mainly an applied science, and the problems being addressed have a strong applied bias, Dr Trudgill argued that we will proceed much more rapidly if we ensure we have a sound understanding of the important principles and mechanisms.

Dr S.R. Gowen (United Kingdom), in his presentation on Chemical control of nematodes: its efficiency and side-effects, indicated that the use of chemicals to control plant-parasitic nematodes has always been an expensive remedy that could be economically justified only on high-value crops such as pineapple, banana, tobacco, potato and some ornamental plants. The first products to be used as nematicides were volatile compounds with fumigant action that required specialized application equipment. Few of these compounds are now in use because of the problems that were discovered concerning toxicity and in some locations unwelcome persistence in the environment that resulted in contamination of groundwater extracted for drinking. The development of organophos-phate and oximecarbamate non-volatile nematicides has enabled the use of chemical treatments for a wider range of situations without the need for specialized application equipment. Unlike most of the fumigants, these products are not phytotoxic at effective doses and multiple applications to growing crops can be made.

Dr Gowen stated that the objectives of a nematicide treatment are to prevent injury to a crop and to limit or prevent the increase of nematode numbers. How effective the treatment is depends greatly on correct conditions for application. Timing, soil moisture, degree of incorporation and rainfall/irrigation can influence nematicide efficacy. With non-volatile compounds economies can be made by treating plants in rows or by spot applications around individual plants rather than as overall broadcast treatments. He added that non-volatile nematicides may be formulated as granular or emulsifiable concentrates. Liquid formulations are easy to apply in drip irrigation systems where dosages can be carefully controlled; however, concentrated formulations are highly toxic and should be used only by qualified personnel. He said that organophosphates and carbamates are of relatively short persistence in topsoil but once they penetrate to deeper soil levels may persist and contaminate aquifers. The long-term effects of nematicide use are not fully understood and disquiet about environmental contamination threatens the future use of these products. Dr Gowen concluded that as components of an integrated approach to nematode control, nematicides can have an important function in decreasing numbers of nematodes to levels at which other remedies may be used to their best advantage.

Dr D.L. Trudgill (United Kingdom) gave a presentation on Problems and perspectives in nematology in the Near East. Applied nematologists need a broad knowledge of crop production systems, plant physiology, etc. relevant to their interests. In practice, they need to collaborate with other specialists, including plant breeders, to achieve their objectives. In such collaboration, it is vital that nematologists are expert in their science and work from basic principles. Scientific progress is interactive and based on a series of small steps. First comes observational information which should be used to formulate hypotheses. Testing of the hypotheses follows and, hopefully, this process leads to increased understanding and further progress. Currently much nematology is observational and does not progress to the development and testing of hypotheses. Thermal time information was used to demonstrate the application of basic principles to applied nematology, particularly to the thermal range of different species and their likely competitive differences. For the future, nematicides will be less available and genetic engineering and biological control agents will probably only be effective against certain problems. Therefore, most farmers will need to rely on more traditional methods including rotation, resistant varieties, improved hygiene, etc. Integration of these approaches with other methods such as solarization may be productive and the role of leading farmers in helping to pioneer such advance should not be underestimated. Overall, training at all levels will be vital and will need to include nematologists, extension workers and farmers.

Dr B. Kerry (United Kingdom) addressed the consultation on Biological control of nematodes: prospects and opportunities. He stated that nematophagous fungi and bacteria occur in some soils in sufficient numbers to provide effective control of several nematode pests. This natural control tends to develop when nematode-susceptible crops are grown in monocultures, and under perennial crops. Where detailed studies have been made the biological control provided by a limited number of fungi and bacteria appears to be predictable and effective. However, in several cases the level of control achieved is inadequate and other control measures are required to reduce nematode populations below damaging levels. Research on soils in which nematode multiplication is suppressed by the activities of nematophagous micro-organisms has helped identify potential biological control agents and key factors which affect their activity.

Dr Kerry added that research on the application of biological agents for control of plant-parasitic nematodes has largely concerned the use of facultative and obligate parasites, but the impacts of rhizosphere bacteria and root-colonizing fungi on the multiplication of nematodes have also been investigated. It is essential to understand the biology and ecology of these organisms for the selection and application of virulent strains. The type of interaction greatly affects the level of population control, damage to the crop and the method of application. Research effort on biological control has concentrated on cyst and root-knot nematodes, which include the most important nematode pests in world agriculture. Those agents that attack infective second-stage juveniles of these nematodes may limit crop damage but have little effect on population control, whereas those agents that infect the developing female have effects similar to partially resistant plant cultivars in that nematode invasion and damage to roots occur, but multiplication is limited. Biological agents have generally provided insufficient control and their integration with other control methods is essential. The host plant greatly affects the efficacy of several agents but this interaction has been little studied. Similarly, the mode of action and the epidemiology of most agents are poorly understood. He concluded by saying that such knowledge is essential for the rational development and application of control strategies using biological agents.

Dr S.R. Gowen (United Kingdom) presented a paper on Alternate strategies for nematode control towards sustainable agriculture. He indicated that the management of plant-parasitic nematodes continues to present problems. For some intensively managed systems, control by use of nematicides may be justified economically but there is increasing pressure to substitute chemical methods with safer non-chemical alternatives. For subsistence and smallholder producers who crop their land continuously, control of nematodes with chemicals has never been feasible and alternative methods have to be developed. He added that a feature of crop intensification is the increased pressure of pests and diseases. The traditional practices of long rotations and fallows are no longer possible in these situations.

Dr Gowen stated that the greatest abundance of plant-parasitic nematodes is to be found in the soil zones where there is a high density of plant roots. Eggs and free-living stages occur in spaces between the soil particles. If the zones of greatest root growth extend to 30 cm, the volume of soil in one square metre is 300 litres. The problems of exerting an influence on nematodes and their eggs in this environment are considerable. Such influences are based on nematode vulnerability to starvation, anaerobic conditions, heat (above 40°C) and desiccation, and also to certain biotic influences such as natural enemies and antagonists and repellents or poisons issuing from plant roots or decaying organic matter. He concluded that the selection of one or more of these potential controlling influences to sustain crop productivity is a challenge that is being taken up with great vigour in many countries.

Dr K.R. Barker (United States), in his presentation on Opportunities for integrated management of plant-parasitic nematodes in the Near East, indicated that an effective blending of traditional and modem technologies is essential to fulfil the increasing demands for food and fibre. For the Near East and much of the world, highly efficient, integrated pest management (IPM) systems for plant-parasitic nematodes must be a key component of this strategy. With the continuing removal of the most efficacious nematicides in most countries, nematode management systems should include a number of compatible strategies (management plans) and tactics (specific weapons). He added that available strategies and respective tactics for combating nematodes are:

· exclusion (quarantine);

· reduction of initial population densities (elimination of established, but limited foci; cultural practices, including crop rotation, inter- and intracropping, cover crops, soil amendments, trap crops, fallow, time of planting and harvesting, and farm hygiene and general culture; vertical resistance; chemical nematicides, and biological agents; and physical treatments such as heat-solarization, flooding, and tillage for destruction of residual, infected roots);

· suppression of nematode reproduction (horizontal resistant cultivars and use of supplemental nematicides);

· restriction of current crop damage (use of tolerant cultivars or deployment of other tactics under the first three strategies).

The integration of strategies and tactics must be based on their relative efficacy, their compatibility/antagonism, and assessments of regional and site-specific nematode problems. Where nematode assay services are unavailable, assessment of some of the major infestations can be made through on-farm, critically timed bio-assays, including root-galling for Meloidogyne spp., or cyst counts for Heterodera/Globodera spp. Dr Barker stated that although considerable progress has been made, much research on damage functions and low-input management tactics/options for nematodes and associated disease complexes remains to be accomplished. Where damage thresholds and related information are unavailable, nematode-hazard indices (relative probability of moderate to severe damage) might be considered. An expert systems approach can facilitate the integration and deployment of these management tactics. The long-term goal of IPM is the interfacing of compatible strategies and tactics for all associated pests and pathogens, including nematodes. He concluded that overall constraints in developing effective IPM programmes, encompassing technology development and transfer, institutional resources and training, related economic and social cultural facets, and environmental factors must also be given high priority.

Dr J. Philis (Cyprus) gave an account of nematological problems with special emphasis on economically important nematodes attacking citrus, potato, grapevine, banana and vegetables. The most important nematodes found being the citrus nematode, potato-cyst nematode, spiral nematodes, dagger nematodes, root-knot and lesion nematodes. He added that chemical control is still the main nematode control measure used in Cyprus. Nematicides are incorporated in the soil before planting as a protection measure, or applied during the season when high nematode populations occur. The use of resistant/tolerant varieties, non-host cropping, fallowing and soil solarization are not widely used due to their limitations. Dr Philis indicated that such methods should be promoted in an IPM programme. To achieve this, awareness of policy-makers is essential. Upgrading infrastructures, provision of facilities, involvement of farmers, conducting applied research and cooperating at the national, regional and international level is of prime importance to ensure satisfactory nematode control measures.

Dr M.A. El-Sherif (Egypt) said that the area of agricultural land in Egypt is limited to the Nile Valley and Delta. The total cultivated area is 7.2 million feddans including 900 000 feddans of newly reclaimed desert land. The most important crops grown in Egypt are cereals (rice, wheat, maize), fibre crops (cotton, flax), sugar cane, food legumes, fruit crops (citrus, grape, mango, stone fruits, etc.), and vegetable crops (tomato, cucumber, etc.). Egypt has 72 nematologists of Ph.D. level, distributed among 12 universities, the Ministry of Agriculture and the National Research Centre. Sixteen of these nematologists are located at the Nematology Research Centre (NRC). Four plant-parasitic nematode genera have been identified and classified as important pathogens that cause severe damage to some important crops in the country: Meloidogyne spp., Rotylenchulus sp., Tylenchulus sp. and Pratylenchus spp. The cyst-forming nematode Heterodera spp., recently became an important pest in Egyptian agriculture.

The majority of farmers are smallholders with less than 2 hectares who cannot afford chemical control of the nematodes. This has led to the increase in nematode population in the soil and thus to the increase of the magnitude of the nematode problem in Egyptian agriculture, especially in the newly reclaimed areas. Rotation is not usually a practical control measure due to the intensive use of the land.

Efforts have been made to limit nematode damage in Egypt through collaboration between nematologists at NRC and those at the Ministry of Agriculture. Also, international collaboration is directed towards combating nematodes in Egyptian agriculture. The search for integrated biological, cultural and physical measures for nematode management that suit the majority of landholders takes first priority.

The NRC at Cairo University should be considered as a focal centre that can offer nematology services (identification, training, etc.) to all North Africa. The centre could also organize regional workshops through which nematologists from the region would exchange information and put forward new strategies for nematode management.

Dr S. Barooti (Iran) stated that because of the variation in climatic conditions in the different parts of the country, the nematode species found in different areas are quite variable. During the past 30 years, 142 species of plant-parasitic nematodes belonging to 41 genera and 15 families have been identified, of which only 12 nematode species cause economic losses. These include Heterodera schachtii, H. avenae, Meloidogyne javanica, M. incognita, Ditylenchus dipsaci, D. destructor, Tylenchulus semipenetrans, Anguina tritici, Pratylenchus penetrans, P. neglectus, Xiphinema index and Longidorus iranicus. Controlling nematode damage in Iran is usually difficult and expensive. Control is achieved by measuring population levels and then using crop rotation, fallow, ploughing and flooding. No chemical control is in use. However, Iranian experts require training on methodology and control of sugar-beet nematodes.

Dr Z.A. Stephan (Iraq) indicated that root-knot nematodes, citrus-root nematodes and seed-gall nematodes are of economic importance to vegetables, citrus and cereals in Iraq. The presence of races of these nematode species should be carefully studied to avoid problems of crop rotation and host resistance breakdown. Crop-loss assessment trials should be carried out for those important nematode species that cause economic damage. Integrated control should be developed by research studies on the effect of cultural and biological factors on nematode populations.

Dr W.I. Abu-Gharbieh (Jordan) stated that nematology research in Jordan began in 1963. Several survey investigations were made and currently nearly 28 genera and over 80 species have been identified. The main nematology laboratory is located at the University of Jordan which is undertaking work in teaching and research. A second laboratory belongs to the Ministry of Agriculture and is located in the Jordan Valley for extension purposes. Only one nematologist with a Ph.D. degree is located at the University of Jordan and two with M.Sc. degrees.

Dr Abu-Gharbieh said that the most important phytonematodes in Jordan include: Meloidogyne, Pratylenchus, Helicotylenchus, Ditylenchus, Tylenchulus semipenetrans, Xiphinema, Longidorus, Heterodera and Anguina. The root-knot nematodes, however, cause the greatest economic damage on a long list of cultivated crops. Because of this these nematodes received the greatest attention in research.

Dr Abu-Gharbieh also recommended an increase in the number of trained nematologists in Jordan, both in the university and in the Ministry of Agriculture; the establishment of a well-equipped central nematology laboratory; and the allocation of adequate funding for research, teaching and extension in nematology.

Dr E.A. Edongali (Libyan Arab Jamahiriya) stated that the Libyan Arab Jamahiriya, a North African country, has a vast area and wide varieties of cultivated crops. Among the most common crops are cereals (wheat, barley, oats, millets and maize), fruit-trees (citrus, date-palm, apricot, almond, olive, grapes, apple, fig and many others), vegetables (potato, cucumber, tomato, leafy vegetables, melons and many others), and forest trees.

He said that owing to the wide variety of hosts, and intermixed cropping systems, plant-parasitic nematodes are well fed and established themselves without any difficulty. Among the most common established nematodes is the root-knot nematode {Meloidogyne spp.). It was found that this nematode is attacking all cultivated crops grown and causing great damage. Others are Tylenchulus semipenetrans, Xiphinema spp., Pratylenchus spp., Rotylenchulus reniformis, Criconemella spp., Longidorus spp., Paralongidorus spp., Heterodera spp., Ditylenchus dipsaci and Globodera spp., etc. The immediate need to tackle these problems is by cooperation between different scientists in the region as well as technical assistance from international agencies.

Dr M.A. Maqbool (Pakistan) indicated that nematode problems have been recognized as one of the great threats to agricultural production. Various surveys conducted from time to time by different workers have revealed that burrowing, cyst, dagger, lance, reniform, root-knot, seed-gall, sheath and stunt nematodes are of common occurrence causing approximately 5 to 20 percent damage to their respective host plants. The up-to-date fauna of plant-parasitic nematodes in Pakistan comprises 294 species, belonging to 56 genera, 36 subfamilies, 21 families, 9 superfamilies, 3 suborders and 3 orders.

The National Nematological Research Centre (NNRC), University of Karachi, is providing nematode diagnostic and advisory services to farmers and developing personnel in this field through teaching M.Sc., M. Phil, and Ph.D. students and training personnel through the organization of workshops, seminars and training courses at the national and international levels. Moreover, this centre is publishing an international journal, Pakistan Journal of Nematology, and has published several books on plant nematology. Host differential testing for identification of species and races of root-knot nematodes has been taken up. Furadan, Temik and indigenous nematicides developed by the Pakistan Council of Scientific and Industrial Research (PCSIR) have been used in nematode control in severely infested fields of sugar cane, citrus, banana, tomato, tobacco, potato and cauliflower. Nematicides have produced marked reductions in the populations and there has been significant increase in crop yield. Besides chemical application, cultural practices, biocontrol agents, organic amendments, plastic mulching and plant extracts have also proved effective in nematode control. Tissue culture technique has been developed to maintain axenic cultures of nematode species, for studying the life cycle and for testing varieties for nematode resistance. Studies on different nematological problems undertaken at the NNRC, University of Karachi; Nematology Laboratory, PCSIR; Crop Diseases Research Institute, National Agricultural Research Centre, Islamabad and NWFP Agriculture University, Peshawar, were reviewed.

Dr A.M. Yassin (the Sudan) indicated that nematological investigations started in the Sudan some three decades ago. Although the effective number of Sudanese nematologists is very limited, several achievements have been made. A total of over 70 species of plant-parasitic nematodes in association with the roots of field crops have been identified; of these, at least six were identified as new species, e.g. Pratylenchus sudanensis, Paratrophurus lobatus and Xiphinema. spp.; as well as two races of Meloidogyne incognita, namely races 1 and 2. Salient nematological problems are root-knot nematodes M. javanica and M. incognita; root-lesion nematodes, especially Pratylenchus sudanensis, and dagger and citrus nematodes. Biological and ecological data for these have been collected. Cooperation with international nematologists was outlined. Dr Yassin indicated that further development of nematology in the country, recruiting more qualified staff, developing technical skills and provision of equipment are essential.

Dr A.S. Al-Hazmi (Saudi Arabia) indicated that his country is witnessing an unprecedented exploitation of its agriculture potential that has never been seen before in its history. Cultivated land has tripled to more than 1.5 million hectares during the past decade. Self-sufficiency in many products and even exports of a few such as wheat, have been achieved. The transformation of the agrodesert to a more intensive modem agro-ecosystem would trigger a population build-up of plant-parasitic nematodes and other plant pests.

Dr Al-Hazmi indicated that plant nematology in Saudi Arabia is relatively very young. The first nematode was only reported in 1957. Although later extensive surveys have shed some light on nematological problems, only a fraction of the true picture has been revealed. Accurate assessment of crop losses and their socio-economic impacts and many nematological aspects are still to be disclosed. The most important nematological problems are the root-knot nematodes on most vegetable crops, the citrus nematode in established citrus orchards and, very recently, the cereal-cyst nematode on wheat. Control measures are mainly through various cultural practices. Use of resistant varieties or nematicides is limited, but practised whenever possible. Efforts are being made to increase efficiency of available methods and to adopt new measures.

Dr Al-Hazmi said that prior to 1980, plant nematology received very little attention compared with other plant protection disciplines, owing to a lack of native nematologists. Since 1980, great efforts have been made in the field of plant nematology which have resulted in good progress and achievements in awareness, education and research in plant nematology. Each of the three colleges of agriculture is offering a three credit nematology course for undergraduates majoring in plant protection. Two other graduate courses are offered for M.Sc. students at the University of Riyadh. Extension and services are officially the responsibility of the Ministry of Agriculture and Water; however, the three colleges are also contributing. Financial aid for research is provided by the government through competitive grants. Although plant nematology has comparatively grown more rapidly than other disciplines of plant protection in recent years, much more work in all aspects of plant nematology remains to be done. For alleviating nematode problems Dr Al-Hazmi recommended education of farmers through simple leaflets and audiovisual aids; demonstration plots and on-site research; training technical personnel; upgrading nematology research, education and extension; making available appropriate books and literature (in Arabic); promoting cooperation and coordination among scientists and authorities concerned; use of healthy planting materials; and enhancement of integrated nematode pest management.

Dr M.E. Okten (Turkey) indicated that his country has a great deal of agricultural production potential, in terms of field crops, fruits and vegetables. Nematological studies in Turkey started during the 1930s. Nematology had long been considered within the scope of entomology, thus little progress was made in developing it as a separate branch. Until recently, plant-parasitic nematodes have drawn less attention than insects, viruses, bacteria and fungi. Nematological studies were concentrated on parasitic nematodes until recent years. In general, economically harmful nematodes are present locally where their host culture plants are cultivated and climate and soil requirements are met. Information is provided to farmers by experts from the Ministry of Agriculture about what measures should be taken to prevent clean areas becoming infected from already infected ones, which is of paramount importance. Since chemical control of nematodes is not practical, cultural measures are being considered. Besides those, internal and external quarantine measures are very important. Although some projects are financed by the Ministry of Agriculture, TUBITAK (Turkish Scientific and Technical Research Agency), DPT (State Department of Planning), and the Atomic Energy Institution of Turkey, there are no projects in the field of nematology supported by foreign aid programmes.

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