The host range, annual cycle and parasitoids of the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) in central and southeast Nigeria

Host range experiments and field sampling in Nigeria produced no evidence that African rice gall midge, Orseolia oryzivora Harris - Gagné, can develop on plants other than Oryza species. Sampling in three outbreak areas during 1994 showed that the insect's annual cycle varied according to the agroecological zone and rice cropping pattern. In the humid forest zone, Orseolia oryzivora persisted through the short dry season on ratoons of cultivated rice Oryza sativa at a rainfed site and on dry season rice crops at an irrigated one. In contrast, at rainfed sites in the moist savannah zone the pest survived the longer dry season on the perennial wild rice O. longistaminata, while ratoons and volunteers of O. sativa provided 'bridges' between the wild host and wet season rice crops. Early in the wet season at rainfed sites, galls of Orseolia oryzivora were not found at high density on wild rice, ratoons or volunteers. The heavy infestations which developed by October resulted primarily from rapid multiplication on rice crops themselves during the wet season. At all 13 sites sampled, the large majority of galls were found on fallow or cropped rice fields, rather than in ditches, bunds or uncultivated wetland, irrespective of the time of year or the hosts involved. From gall dissections, the parasitoids Aprostocetus procerae (Risbec) and Platygaster diplosisae Risbec caused over 30% mortality at some sites by October but generally increased too late to prevent crop damage. Implications of the results for the management of Orseolia oryzivora are discusse

Physical and Pasting Properties of ‘Ofada’ Rice (Oryza sativa L.) Varieties

ABSTRACTIn this study, grain physical and pasting properties of ofada rice cultivated in South-West Nigeria was evaluated using Standard Evaluation System (SES) for rice with the aim of providing basic information for brand development and utilization of ofada in the development of novel food products. Results showed that size and shape of ofada rice ranged from 5.9 to 9.0mm and 1.8 to 3.0mm respectively. The 1000-grain weight was between 24.0 to 31.0g. Percentage hull was significantly different among the cultivars, ranging from 16 to 21. Peak viscosity ranged between 112.7 and 152.8 BU, minimum, setback and final viscosities varied from 80.3 to 117.2 BU, 104.0 to 143.3BU and 190.8 and 232.3 BU respectively. Gelatinization temperature was not significantly different and varied between 64.1 to 64.7°C. Significant difference (p<5%) was observed among the samples in terms of minimum setback and final viscosities respectively. Significant negative association was observed between kernel length and gelatinization temperature (r=– 0.65), setback and gelatinization temperature (r=– 67) while positive correlation was observed between breakdown viscosity and peak viscosity (r=0.86). The good pasting behaviour makes ofada flour good material for the production of stiff dough products, better palatability and water binding capacity while physical qualities give ofada an advantage during milling. This attributes could be exploited for the development of new varieties and utilization in food development of the ofada rice value-chain

Distribution of the African rice gall midge, Orseolia oryzivora Harris and Gagne and its parasitoids in Nigeria

The African rice gall midge, Orseolia oryzivora Harris and Gagné has become one of the major biotic constraints to rice production in Nigeria. A survey of gall midge distribution in Nigeria showed that the pest was common in the savannah and forest zones on rice grown under lowland ecologies. Endemic areas were identified which could serve as ‘hot spots' for varietal screening. Indigenous parasitoids of the pest were identified as: Platygaster diplosisae Risbec, Aprostocetus pachydiplosisae Risbec and Aphanogmus spp. The dominant parasitoid was, however, P. diplosisae

Natural biological control of African rice gall midge in Nigeria: IITA research guide, No. 37

The African rice gall midge (ARGM), Orseolia oryzivora Harris & Gagne, has recently emerged as an important insect pest of rice in many African countries. Infestation can result in total crop failure. Naturally occurring biological control agents have been identified in Nigeria that can reduce ARGM to tolerable levels. Researchers observed a large percentage of parasitized galls in unsprayed rice fields. Naturally occurring biological control agents attack ARGM population, thus reducing the severity and frequency of attack. Control agents reduce ARGM populations free of charge to the farmers. Natural enemies of ARGM in Nigeria so far discovered are parasitoids

Les insectes nuisibles du riz au champ en Afrique: biologie et methode de lutte

Les inseeles nuisibles sont une contrainle principale II la production du riz en Afrique et dans d'autres parties du monde. lis occasionnent toujours des pertes de rendement de rordre de 30 II 100'*. Les mesures de lutle comprennent les methodes culturales el biologiques, la resistance de la plante-hote et les me-thodes chimiques. Les methodes chimiques presentent plusieurs inconvenients. La lutte integree contre les depredateurs combine les avantages de plusieurs me-thodes de lutte pour parvenir II des mesures ecologi-quement saines. Un bon systeme de lutte contre ces in-sectes nuisibles exige une connaissance adequate de l'identite et de la biologie des ravageurs et de leurs en-nemis nature Is

Field varietal screening against African rice gall midge: IITA research guide, No. 34

The African rice gall midge (ARGM) is an insect pest of rice in Africa which has recently attained outbreak levels in many African countries. Infestation can result in total crop failure. The use of insecticides to control the pest has several disadvantages. Cultivation of resistant varieties is the best control method. However, resistance is location specific. Screening for resistance over three to four year at the same location helps to identify resistant varieties for use by farmers

Biology, status and management of rice insect pest in Nigeria

Rice insect pest management in Nigeria is compartmentalized; literature documenting the status of research on the biology and significance of insect pests and on their management, has therefore been reviewed. A holistic, broadly based, multidisciplinary pest-management research approach is suggested. Because of the immense benefits that integrated pest management (IPM) can provide, it is urged that steps be taken immediately to develop and implement IPM for rice insects in Nigeria