Nematodes - cowpea
Contributors to this section: IITA, Nigeria (M. Ayodele, L. Kumar).
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Scientific name
Meloidogyne arenaria.
Other scientific names
Meloidogyne incognita (Kofoid & White, 1919) Chitwood 1949
Oxyuris incognita Kofoid & White, 1919
Meloidogyne incognita acrita Chitwood, 1949
Meloidogyne acrita Chitwood, 1949
Importance
High
Significance
The nematode attacks many major food crops resulting in reduction in quality and quantity of food and feed .Yield loss ranges from 5%- to complete loss (Sasser and Carter, 1984).
Symptoms
The nematode affects the flowering, podding, seedling and vegetative growing stages. The leaves, roots and whole plant are also attacked by the nematode causing different symptoms on:
roots/ corms/ tubers: galls, abnormal formation and function of root system and blockage of; the vascular cylinder.
stem ( above the ground )symptoms : patchy, stunted growth; discoloration and
leaf : chlorosis, wilting
whole plant : stunting, reduced yield in quantity and quality; premature; death.
Hosts
The nematode has alarge host range which includes monocotyledons, dicotyledons, herbaceous and woody plants.
The major hosts include Vigna unguiculata (cowpea), Abelmoschus esculentus (okra), Arachis hypogaea (groundnut), Avena sativa (oats), Capsicum frutescens (chilli), Citrullus lanatus (watermelon), Coffea arabica (arabica coffee), Cucumis sativus (cucumber), Cucurbita pepo (ornamental gourd), Daucus carota (carrot), Glycine max (soyabean), Gossypium hirsutum (Bourbon cotton), Hordeum vulgare (barley), Ipomoea batatas (sweet potato), Lycopersicon esculentum (tomato), Medicago sativa (lucerne), Musa (banana), Nicotiana tabacum (tobacco), Oryza sativa (rice), Passiflora edulis (passionfruit), Phaseolus vulgaris (common bean), Pisum sativum (pea), Prunus persica (peach), Vitis vinifera (grapevine), and Zea mays (maize).
Geographic distribution
Cosmopolitan
Biology and transmission
Not reported
Detection/indexing methods used at IITA
General methods for the detection of all nematodes
A: On seeing suppressed growth/decreased production in crop plants
- Stage 1: Look for and assess symptoms of nematode damage
- Stage 2: Collect soil and plant tissue samples
- Stage 3: Extract nematodes from samples
- Stage 4: Identify nematodes
- Stage 5: Nematode density assessment
- Stage 6: Nematode damage analysis
- Stage 7: Management decision
B : Direct examination of plant material
- Wash the plant tissue/seed under a gentle stream of water, or place in a bowl of water for a few minutes, to remove soil and debris, taking care not to dislodge ectoparasitic nematodes feeding or attached on the outside of roots.
- Cut the plant tissue into ~2cm pieces with a pair of sharp scissors or knife.
- Place the plant tissue into an open Petri dish that has water in the base
- For immediate observation tease open the tissue with the aid of mounted needles and forceps to release the nematodes from the plant tissue. This is suitable for sedentary endoparasites.
- If the plant tissue contains migratory nematodes it may be useful to leave in a Petri dish overnight or longer even. Nematodes will migrate out of the tissue into the water.
- Nematodes can then be picked under the stereomicroscope for identification or preserved (and stained) and/or sent for further identification
- Infected materials are discarded by incineration
Treatment/control
- Plant resistant varieties.
- Crop rotation 2 yearly interval
- Use of nematicides as soil fumigants
Procedures in case of positive test at IITA
- Discard. Not acceptable for international distribution
References and further reading
Sasser JN, Carter CC. 1984. Overview of the International Meloidogyne Project, 1975-1984, pp. 19 - 24. In: Sasser JN, Carter CC, editors. An advanced treatise on Meloidogyne, Vol. 1 Biology and control. Raleigh, NC: A Cooperative Publication of the Department of Plant Pathology and Genetics, North Carolina State University, and the United States Agencey for International Development
Scientific name
Rotylenchulus reniformis
Other scientific names
Rotylenchulus leiperi (Das) Loof & Oostenbrunk, 1961
Rotylenchulus queirozi (Lordello & Cesnik) Sher, 1961
Rotylenchulus stakmani Husain & Khan, 196
Importance
High
Significance
The nematode is a pest of economic importance of cowpea , cotton, pineapple, sweet potato and soyabean, banana, aubergine, cabbage, okra, melon, pigeon pea, tea and tobacco.
There are no quantified reports on yield losses of cowpea due to attack by this nematode, although losses ranging from 9.5-17.4% and 40-60% due to attack by this nematode have been reported on cotton in India, and Egypt (Bridge, 1992; Robinson et. al., 1997).
Symptoms
Symptoms exhibited on all plant parts on:
Leaf : chlorosis
Seed/seedling : delayed emergence
Whole plant : stunted growth, wilting, collapse (Gaur and Perry, 1991).
Hosts
R. reniformis has a wide host. (Robinson et al., 1997) with major hosts such as: Vigna unguiculata (cowpea), Abelmoschus esculentus (okra), Ananas comosus (pineapple), Brassica oleracea var. capitata (cabbage), Cajanus cajan (pigeon pea), Carica papaya (papaw), Citrus , Cucumis melo (melon), Cucurbitaceae (cucurbits), Glycine max (soyabean), Gossypium (cotton), Gossypium hirsutum (Bourbon cotton), Ipomoea batatas (sweet potato), Lycopersicon esculentum (tomato), Musa (banana), Phaseolus (beans), Solanum melongena (aubergine), and some recorded minor hosts include: Arachis hypogaea (groundnut), Artocarpus altilis (breadfruit), Beta vulgaris (beetroot), Brassica oleracea (cabbages, cauliflowers), Solanum tuberosum (potato), Sorghum halepense (Johnson grass), Theobroma cacao (cocoa), triticum aestivum (wheat), Vicia faba (broad bean), Vigna mungo (black gram), Vigna radiata (mung bean), Vitis vinifera (grapevine), Xanthosoma sagittifolium ( Cocoyam),and Zea mays (maize).
Geographic distribution
R. reniformis is very widely distributed in the subtropical and tropical regions of the world and also in some warm temperate localities in Europe and other countries.
Biology and transmission
R. reniformis is a soil inhabiting semi-endoparasite of roots. (Robinson et. al., 1997). The life cycle from egg to egg can be as short as 3 weeks
The nematode has biological races. In India, the nematode is reported to have at least two races on the basis of parasitism on three hosts, one parasitic on cowpea, castor and cotton, the other parasitic only on cowpea.
Races have also reported from USA, Cuba and Japan (Dasgupta and Seshadri, 1971; Robinson et al., 1997.
Detection/indexing methods used at IITA
Direct examination of plant material
- Wash the plant tissue/seed under a gentle stream of water, or place in a bowl of water for a few minutes, to remove soil and debris, taking care not to dislodge ectoparasitic nematodes feeding or attached on the outside of roots.
- Cut the plant tissue into ~2cm pieces with a pair of sharp scissors or knife.
- Place the plant tissue into an open Petri dish that has water in the base
- For immediate observation tease open the tissue with the aid of mounted needles and forceps to release the nematodes from the plant tissue. This is suitable for sedentary endoparasites.
- If the plant tissue contains migratory nematodes it may be useful to leave in a Petri dish overnight or longer even. Nematodes will migrate out of the tissue into the water.
- Nematodes can then be picked under the stereomicroscope for identification or preserved (and staining the roots and nematodes in acid fuchsin or methyl blue and examining under a microscope.) and/or sent for further identification
Treatment
- Plant resistant varieties
- Crop rotation 2 yearly interval
- Use of nematicides as soil fumigants
Procedures in case of positive test at IITA
- Discard. Not acceptable for international distribution
- Infected materials are discarded by incineration
References and further references
Bridge J. 1992. Nematodes. In: Hillocks RJ, editor. Cotton diseases, Wallingford, UK: CAB International, 331-353.
Dasgupta DR, Seshadri AR. 1971. Races of the reniform nematode, Rotylenchulus reniformis Linford and Oliveira, 1940. Indian Journal of Nematology, 1:21-24.
Gaur HS, Perry RN. 1991. The biology and control of the plant parasitic nematode Rotylenchulus reniformis. Agricultural Zoology Reviews, 4:177-212.
Robinson AF, Inserra RN, Caswell-Chen EP, Vovlas N, Troccoli A. 1997. Rotylenchulus species: identification, distribution, host ranges, and crop plant resistance. Nematropica, 27(2):127-180
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