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International Centre of Insect Physiology and Ecology

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Articles 361 - 390 of 443

Full-Text Articles in Agricultural Science

Plant Growth-Promoting Rhizobacteria Do Not Pose Any Deleterious Effect On Cowpea And Detectable Amounts Of Ethylene Are Produced, Olubukola O. Babalola, Abiodun I. Sanni, George D. Odhiambo, Baldwyn Torto Jun 2007

Plant Growth-Promoting Rhizobacteria Do Not Pose Any Deleterious Effect On Cowpea And Detectable Amounts Of Ethylene Are Produced, Olubukola O. Babalola, Abiodun I. Sanni, George D. Odhiambo, Baldwyn Torto

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The use of trap crops such as cowpea could reduce the effects of the root parasitic weed, Striga hermonthica and its subsequent constraints on the growth of cereals. Certain bacteria could augment the trap crop stimulatory effect. We studied the effect of three bacteria introduced to the rhizosphere of three cowpea varieties at planting. Number of days to cowpea flowering was noted and at harvest, data were collected on pod characteristics and biomass. Means of data subjected to ANOVA were compared using Tukey's Studentized Range Test. We analysed bacterial headspace volatiles for ethylene by gas chromatography and gas chromatography-mass spectrometry. …

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C-Methylated And C-Prenylated Isoflavonoids From Root Extract Of Desmodium Uncinatum, Salome M. Guchu, Abiy Yenesew, Muniru K. Tsanuo, Nicholas K. Gikonyo, John A. Pickett, Antony M. Hooper, Ahmed Hassanali Mar 2007

C-Methylated And C-Prenylated Isoflavonoids From Root Extract Of Desmodium Uncinatum, Salome M. Guchu, Abiy Yenesew, Muniru K. Tsanuo, Nicholas K. Gikonyo, John A. Pickett, Antony M. Hooper, Ahmed Hassanali

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A pterocarpan, 1,9-dihydroxy-3-methoxy-2-methylpterocarpan (named uncinacarpan) and two isoflavanones, 5,7-dihydroxy-2′,3′,4′-trimethoxy-6-(3-methylbut-2-enyl)isoflavanone (named uncinanone D) and 5,4′-dihydroxy-7,2′-dimethoxy-6-methylisoflavanone (named uncinanone E), were isolated from the CH2Cl2 root extract of Desmodium uncinatum (Jacq.) DC and characterised by spectroscopic methods. In addition, a rare pterocarpan edudiol and two known abietane diterpenes, 7-oxo-15-hydroxydehydroabietic acid and 7-hydroxycallitrisic acid were identified. The fraction of the root extract that was analysed induced germination of Striga hermonthica seeds, but none of the isolated compounds showed this activity. © 2006 Elsevier Ltd. All rights reserved.

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Environmental Abundance Of Anopheles (Diptera: Culicidae) Larval Habitats On Land Cover Change Sites In Karima Village, Mwea Rice Scheme, Kenya, Benjamin G. Jacob, Ephantus Muturi, Patrick Halbig, Joseph Mwangangi, R. K. Wanjogu, Enock Mpanga, Jose Funes, Josephat Shililu, John Githure, James L. Regens, Robert J. Novak Jan 2007

Environmental Abundance Of Anopheles (Diptera: Culicidae) Larval Habitats On Land Cover Change Sites In Karima Village, Mwea Rice Scheme, Kenya, Benjamin G. Jacob, Ephantus Muturi, Patrick Halbig, Joseph Mwangangi, R. K. Wanjogu, Enock Mpanga, Jose Funes, Josephat Shililu, John Githure, James L. Regens, Robert J. Novak

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A study was carried out at Karima Village in the Mwea Rice Irrigation Scheme in Kenya to assess the impact of rice husbandry and associated land cover change for mosquito larval abundance. A multi-temporal, land use land cover (LULC) classification dataset incorporating distributions of Anopheles arabiensis aquatic larval habitats was produced in ERDAS Imagine version 8.7 using combined images from IKONOS at 4m spatial resolution from 2005 and Landsat Thematic Mapper (TM)™ classification data at 30-meters spatial resolution from 1988 for Karima. Of 207 larval habitats sampled, most were either canals (53.4%) or paddies (45.9%), and only one habitat was …

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Antibacterial Activity Of Apis Mellifera L. Propolis Collected In Three Regions Of Kenya, Elliud M. Muli, J. M. Maingi Jan 2007

Antibacterial Activity Of Apis Mellifera L. Propolis Collected In Three Regions Of Kenya, Elliud M. Muli, J. M. Maingi

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The present study aimed at investigating the susceptibility of the microorganisms Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis to ethanolic extracts of propolis (EEP) from three regions of Kenya (Taita, Tana and Samburu). Propolis was extracted using four different concentrations of ethanol: pure, 70%, 50%, and 30%. Ethanol (70%) and Streptomycin were used as controls. The agar diffusion method using filter paper disks was employed. Antibacterial activity was determined as an equivalent of the inhibition zones diameters (in millimeters) after incubation at 37°C for 24h. Significant differences in the antibacterial activities of propolis were observed among …

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Larval Habitat Dynamics And Diversity Of Culex Mosquitoes In Rice Agro-Ecosystem In Mwea, Kenya, Ephantus J. Muturi, Josephat I. Shililu, Weidong Gu, Benjamin G. Jacob, John I. Githure, Robert J. Novak Jan 2007

Larval Habitat Dynamics And Diversity Of Culex Mosquitoes In Rice Agro-Ecosystem In Mwea, Kenya, Ephantus J. Muturi, Josephat I. Shililu, Weidong Gu, Benjamin G. Jacob, John I. Githure, Robert J. Novak

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Introduction of irrigation projects in developing nations has often been blamed for aggravating the problem of mosquito-borne diseases by creating ideal larval habitats for vector mosquitoes. However, whereas several studies have demonstrated the relationship between malaria vectors and irrigation, little work has been done on culicine mosquitoes despite their potential in transmission of filariasis and arboviruses and their significant biting nuisance in these areas. This study examined the diversity of Culex mosquito fauna and their larval habitats at two sites (Murinduko and Kiamachiri) in Mwea, Kenya over a 12-month period. The habitat types present at each site within a 200-meter …

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Distribution And Relative Importance Of Lepidopteran Cereal Stemborers And Their Parasitoids In Uganda, T. Matama-Kauma, F. Schulthess, J. A. Ogwang, J. M. Mueke, C. O. Omwega Jan 2007

Distribution And Relative Importance Of Lepidopteran Cereal Stemborers And Their Parasitoids In Uganda, T. Matama-Kauma, F. Schulthess, J. A. Ogwang, J. M. Mueke, C. O. Omwega

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Infestation levels and parasitism of lepidopteran stemborers on maize were assessed in four agroecological zones (AEZ) in Uganda. The indigenous noctuid Busseola fusca Fuller (Noctuidae) and the invasive Chilo partellus Swinhoe (Crambidae) were the most important stemborers recorded. C. partellus represented 77% of the stemborers in the Eastern AEZ while B. fusca was dominant in the other AEZs, accounting for 60-79%. The proportion of infested plants was between 16% and 45% and borer density between 0.2 and 1.0 borers per plant. There was no clear relationship between damage and stem tunneling, which is often used to estimate yield loss. Telenomus …

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Farmers' Perceptions Of Importance, Control Practices And Alternative Hosts Of Maize Stemborers In Uganda, T. Kalule, Z. R. Khan, G. Bigirwa, J. Alupo, S. Okanya, J. A. Pickett, L. J. Wadhams Dec 2006

Farmers' Perceptions Of Importance, Control Practices And Alternative Hosts Of Maize Stemborers In Uganda, T. Kalule, Z. R. Khan, G. Bigirwa, J. Alupo, S. Okanya, J. A. Pickett, L. J. Wadhams

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A survey was conducted in Tororo, Bugiri and Kapchorwa districts in eastern and northeastern Uganda on farmers' perceptions of constraints in maize production. Farmers in Tororo and Bugiri consistently ranked stemborers and striga as the major production constraints in maize growing, while those in Kapchorwa ranked stemborers and lack of capital as the most important. Approximately 35 and 40% of the farmers in Tororo and Bugiri, respectively, identified stemborers as the 'caterpillar' that destroys their maize. In Kapchorwa, 50% of the farmers identified stemborers. Pesticide application was the most common control measure while the use of indigenous and cultural control …

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Survival Of Immature Anopheles Arabiensis (Diptera: Culicidae) In Aquatic Habitats In Mwea Rice Irrigation Scheme, Central Kenya, Joseph M. Mwangangi, Ephantus J. Muturi, Josephat Shililu, Simon M. Muriu, Benjamin Jacob, Ephantus W. Kabiru, Charles M. Mbogo, John Githure, Robert Novak Nov 2006

Survival Of Immature Anopheles Arabiensis (Diptera: Culicidae) In Aquatic Habitats In Mwea Rice Irrigation Scheme, Central Kenya, Joseph M. Mwangangi, Ephantus J. Muturi, Josephat Shililu, Simon M. Muriu, Benjamin Jacob, Ephantus W. Kabiru, Charles M. Mbogo, John Githure, Robert Novak

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Background: The survivorship and distribution of Anopheles arabiensis larvae and pupae was examined in a rice agroecosystem in Mwea Irrigation Scheme, central Kenya, from August 2005 to April 2006, prior to implementation of larval control programme. Methods: Horizontal life tables were constructed for immatures in semi-field condition. The time spent in the various immature stages was determined and survival established. Vertical life tables were obtained from five paddies sampled by standard dipping technique. Results: Pre-adult developmental time for An. arabiensis in the trays in the experimental set up in the screen house was 11.85 days from eclosion to emergence. The …

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Development Of Pcr-Based Chloroplast Dna Markers That Characterize Domesticated Cowpea (Vigna Unguiculata Ssp. Unguiculata Var. Unguiculata) And Highlight Its Crop-Weed Complex, Y. Feleke, R. S. Pasquet, P. Gepts Nov 2006

Development Of Pcr-Based Chloroplast Dna Markers That Characterize Domesticated Cowpea (Vigna Unguiculata Ssp. Unguiculata Var. Unguiculata) And Highlight Its Crop-Weed Complex, Y. Feleke, R. S. Pasquet, P. Gepts

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In 1992, Vaillancourt and Weeden discovered a very important mutation for studying cowpea evolution and domestication. A loss of a BamHI restriction site in chloroplast DNA characterized all domesticated accessions and a few wild (Vigna unguiculata ssp. unguiculata var. spontanea) accessions. In order to screen a larger number of accessions, primers were designed to check this mutation using PCR RFLP or direct PCR methods. Using these new primers, 54 domesticated cowpea accessions and 130 accessions from the wild progenitor were screened. The absence of haplotype 0 was confirmed within domesticated accessions, including primitive landraces from cultivar-groups Biflora and Textilis, suggesting …

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Electrophysiological Responses Of The Lepidopterous Stemborers Chilo Partellus And Busseola Fusca To Volatiles From Wild And Cultivated Host Plants, M. A. Birkett, K. Chamberlain, Z. R. Khan, J. A. Pickett, T. Toshova, L. J. Wadhams, C. M. Woodcock Nov 2006

Electrophysiological Responses Of The Lepidopterous Stemborers Chilo Partellus And Busseola Fusca To Volatiles From Wild And Cultivated Host Plants, M. A. Birkett, K. Chamberlain, Z. R. Khan, J. A. Pickett, T. Toshova, L. J. Wadhams, C. M. Woodcock

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The stemborers Chilo partellus and Busseola fusca are major pests of subsistence cereal farming in Africa. Volatiles released by two cultivated hosts, sorghum and maize (Sorghum bicolor and Zea mays), and two wild grass hosts, Pennisetum purpureum and Hyparrhenia tamba, were collected by air entrainment. Electrophysiologically active components in these samples were detected by coupled gas chromatography-electroantennography (GC-EAG), and the active peaks identified by gas chromatography-mass spectrometry. A total of 41 compounds were identified from the four plant species, all of which, as well as two unidentified compounds, elicited an electrophysiological response from one or both of the stemborers. The …

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A Grid-Based Infrastructure For Ecological Forecasting Of Rice Land Anopheles Arabiensis Aquatic Larval Habitats, Benjamin G. Jacob, Ephantus J. Muturi, Jose E. Funes, Josephat I. Shililu, John I. Githure, Ibulaimu I. Kakoma, Robert J. Novak Oct 2006

A Grid-Based Infrastructure For Ecological Forecasting Of Rice Land Anopheles Arabiensis Aquatic Larval Habitats, Benjamin G. Jacob, Ephantus J. Muturi, Jose E. Funes, Josephat I. Shililu, John I. Githure, Ibulaimu I. Kakoma, Robert J. Novak

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Background: For remote identification of mosquito habitats the first step is often to construct a discrete tessellation of the region. In applications where complex geometries do not need to be represented such as urban habitats, regular orthogonal grids are constructed in GIS and overlaid on satellite images. However, rice land vector mosquito aquatic habitats are rarely uniform in space or character. An orthogonal grid overlaid on satellite data of rice-land areas may fail to capture physical or man-made structures, i.e paddies, canals, berms at these habitats. Unlike an orthogonal grid, digitizing each habitat converts a polygon into a grid cell, …

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Combined Control Of Striga Hermonthica And Stemborers By Maize-Desmodium Spp. Intercrops, Zeyaur R. Khan, John A. Pickett, Lester J. Wadhams, Ahmed Hassanali, Charles A.O. Midega Sep 2006

Combined Control Of Striga Hermonthica And Stemborers By Maize-Desmodium Spp. Intercrops, Zeyaur R. Khan, John A. Pickett, Lester J. Wadhams, Ahmed Hassanali, Charles A.O. Midega

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The African witchweed (Striga spp.) and lepidopteran stemborers are two major biotic constraints to the efficient production of maize in sub-Saharan Africa. Previous studies had shown the value of intercropping maize with Desmodium uncinatum in the control of both pests. The current study was conducted to assess the potential role of other Desmodium spp., adapted to different agro-ecologies, in combined control of both pests in Kenya. Treatments consisted of intercropped plots of a Striga hermonthica- and stemborer-susceptible maize variety and one Desmodium sp. or cowpea, with a maize monocrop plot included as a control. S. hermonthica counts and stemborer damage …

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Population Models For Threshold-Based Control Of Tetranychus Urticae In Small-Scale Kenyan Tomato Fields And For Evaluating Weather And Host Plant Species Effects, Markus Knapp, Ibrahima Sarr, Gianni Gilioli, Johann Baumgärtner Aug 2006

Population Models For Threshold-Based Control Of Tetranychus Urticae In Small-Scale Kenyan Tomato Fields And For Evaluating Weather And Host Plant Species Effects, Markus Knapp, Ibrahima Sarr, Gianni Gilioli, Johann Baumgärtner

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The spatial distribution of motile life stages of the two-spotted spider mite Tetranychus urticae Koch in Kenyan small-scale tomato fields was described by Taylor's power law and an enumerative sampling plan was designed for research purposes. The exponential increase of T. urticae populations during three growing seasons permits the development and use of a simple exponential model for the design of a threshold-based chemical control system. For this purpose, a critical threshold of 440 motile mites per sample unit at the end of the growing season (12 weeks after transplanting) was translated into a proportion of 0.83 infested units in …

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Spatially Targeting Culex Quinquefasciatus Aquatic Habitats On Modified Land Cover For Implementing An Integrated Vector Management (Ivm) Program In Three Villages Within The Mwea Rice Scheme, Kenya, Benjamin G. Jacob, Josephat Shililu, Ephantus J. Muturi, Joseph M. Mwangangi, Simon M. Muriu, Jose Funes, John Githure, James L. Regens, Robert J. Novak May 2006

Spatially Targeting Culex Quinquefasciatus Aquatic Habitats On Modified Land Cover For Implementing An Integrated Vector Management (Ivm) Program In Three Villages Within The Mwea Rice Scheme, Kenya, Benjamin G. Jacob, Josephat Shililu, Ephantus J. Muturi, Joseph M. Mwangangi, Simon M. Muriu, Jose Funes, John Githure, James L. Regens, Robert J. Novak

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Background: Continuous land cover modification is an important part of spatial epidemiology because it can help identify environmental factors and Culex mosquitoes associated with arbovirus transmission and thus guide control intervention. The aim of this study was to determine whether remotely sensed data could be used to identify rice-related Culex quinquefasciatus breeding habitats in three rice-villages within the Mwea Rice Scheme, Kenya. We examined whether a land use land cover (LULC) classification based on two scenes, IKONOS at 4 m and Landsat Thematic Mapper at 30 m could be used to map different land uses and rice planted at different …

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Diel Periodicity In The Production Of Green Leaf Volatiles By Wild And Cultivated Host Plants Of Stemborer Moths, Chilo Partellus And Busseola Fusca, K. Chamberlain, Z. R. Khan, J. A. Pickett, T. Toshova, L. J. Wadhams Mar 2006

Diel Periodicity In The Production Of Green Leaf Volatiles By Wild And Cultivated Host Plants Of Stemborer Moths, Chilo Partellus And Busseola Fusca, K. Chamberlain, Z. R. Khan, J. A. Pickett, T. Toshova, L. J. Wadhams

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The volatile chemicals produced by four poaceous plant species, blue thatching grass, Hyparrhenia tamba, Napier grass, Pennisetum purpureum, sorghum, Sorghum bicolor, and maize, Zea mays, which are host plants for the lepidopterous stemborers, Chilo partellus and Busseola fusca, were collected by air entrainment and analyzed by gas chromatography. The total quantities of volatiles collected hourly, over a 9-hr period, from P. purpureum and H. tamba showed an approximately hundredfold increase in the first hour of the scotophase. Thereafter, the amount decreased rapidly to levels present during photophase. Although onset of scotophase also triggered an increase in quantities of volatiles collected …

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The Effect Of Nitrogen Fertilizer Application To Maize And Sorghum On The Bionomics Of Chilo Partellus (Lepidoptera: Crambidae) And The Performance Of Its Larval Parasitoid Cotesia Flavipes (Hymenoptera: Braconidae), N. Jiang, F. Schulthess Dec 2005

The Effect Of Nitrogen Fertilizer Application To Maize And Sorghum On The Bionomics Of Chilo Partellus (Lepidoptera: Crambidae) And The Performance Of Its Larval Parasitoid Cotesia Flavipes (Hymenoptera: Braconidae), N. Jiang, F. Schulthess

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Laboratory and field trials were conducted to evaluate the effect of plant species (maize, sorghum), plant age (young, middle, old) and four different nitrogen fertilization levels (N0-N3) on the bionomics of the invasive crambid Chilo partellus and the performance of its braconid larval parasitoid Cotesia flavipes. Plant N varied significantly between N0 and N1-N3, but the differences among the latter were not significant. Intrinsic rates of increase and net-reproductive rates of C. partellus followed the same trends: they were lowest with N0 and similar among the other treatments. On maize only, mortality of C. partellus and parasitism by C. flavipes …

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Relationships Of Intercropped Maize, Stem Borer Damage To Maize Yield And Land-Use Efficiency In The Humid Forest Of Cameroon, A. Chabi-Olaye, C. Nolte, F. Schulthess, C. Borgemeister Oct 2005

Relationships Of Intercropped Maize, Stem Borer Damage To Maize Yield And Land-Use Efficiency In The Humid Forest Of Cameroon, A. Chabi-Olaye, C. Nolte, F. Schulthess, C. Borgemeister

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Stem borers are the most important maize pests in the humid forest zone of Cameroon. Field trials were conducted in the long and short rainy seasons of 2002 and 2003 to assess the level of damage and yield reductions caused by stem borers in monocropped maize and in maize intercropped with non-host plants such as cassava, cowpea and soybean. The intercrops were planted in two spatial arrangements, i.e. alternating hills or alternating rows. All intercrops and the maize monocrop were grown with and without insecticide treatment for assessment of maize yield loss due to borer attacks. The land-use efficiency of …

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Effects Of Grain Legumes And Cover Crops On Maize Yield And Plant Damage By Busseola Fusca (Fuller) (Lepidoptera: Noctuidae) In The Humid Forest Of Southern Cameroon, A. Chabi-Olaye, C. Nolte, F. Schulthess, C. Borgemeister Jun 2005

Effects Of Grain Legumes And Cover Crops On Maize Yield And Plant Damage By Busseola Fusca (Fuller) (Lepidoptera: Noctuidae) In The Humid Forest Of Southern Cameroon, A. Chabi-Olaye, C. Nolte, F. Schulthess, C. Borgemeister

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Field trials were run in the humid forest zone of Cameroon to investigate the effects of crop rotation, cover crops and bush fallow on infestations by the noctuid stemborer Busseola fusca (Fuller) and on yield of maize. A continuous maize production system was compared with crop sequence systems, in which maize followed a grain legume (cowpea, soybean), cover crop (mucuna, pigeon pea) or a bush fallow. Compared to the continuous maize cropping system, maize in the crop sequence with legume and fallow systems had significantly higher leaf and stem nitrogen content at 35 and 63 days after planting (DAP), respectively. …

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Life Tables, Key Factor Analysis And Density Relations Of Natural Populations Of The Spotted Maize Stemborer, Chilo Partellus (Lepidoptera: Crambidae), Under Different Cropping Systems At The Kenyan Coast, C. A.O. Midega, C. K.P.O. Ogol, W. A. Overholt Jun 2005

Life Tables, Key Factor Analysis And Density Relations Of Natural Populations Of The Spotted Maize Stemborer, Chilo Partellus (Lepidoptera: Crambidae), Under Different Cropping Systems At The Kenyan Coast, C. A.O. Midega, C. K.P.O. Ogol, W. A. Overholt

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Studies were conducted at Mtwapa, in the coastal area of Kenya, during the long and short rains of 1999 and 2000 to evaluate interaction of mortality factors in lowering Chilo partellus (Swinhoe) populations in diverse agroecosystems. Treatments consisted of hedgerows of leucaena only, gliricidia only, alternating rows of leucaena and gliricidia, and three plots without trees. During the cropping seasons, maize was planted between the hedgerows while a row of cowpea was planted between the rows of maize. One of the plots without trees was planted to an intercrop of maize and cowpea. The remaining two plots without trees were …

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Comparative Performance Of The Mbita Trap, Cdc Light Trap And The Human Landing Catch In The Sampling Of Anopheles Arabiensis, An. Funestus And Culicine Species In A Rice Irrigation In Western Kenya, Evan M. Mathenge, Gedion O. Misiani, David O. Oulo, Lucy W. Irungu, Paul N. Ndegwa, Tom A. Smith, Gerry F. Killeen, Bart G.J. Knols Jan 2005

Comparative Performance Of The Mbita Trap, Cdc Light Trap And The Human Landing Catch In The Sampling Of Anopheles Arabiensis, An. Funestus And Culicine Species In A Rice Irrigation In Western Kenya, Evan M. Mathenge, Gedion O. Misiani, David O. Oulo, Lucy W. Irungu, Paul N. Ndegwa, Tom A. Smith, Gerry F. Killeen, Bart G.J. Knols

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Background: Mosquitoes sampling is an important component in malaria control. However, most of the methods used have several shortcomings and hence there is a need to develop and calibrate new methods. The Mbita trap for capturing host-seeking mosquitoes was recently developed and successfully tested in Kenya. However, the Mbita trap is less effective at catching outdoor-biting Anopheles funestus and Anopheles arabiensis in Madagascar and, thus, there is need to further evaluate this trap in diverse epidemiological settings. This study reports a field evaluation of the Mbita trap in a rice irrigation scheme in Kenya. Methods: The mosquito sampling efficiency of …

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Effect Of Agroecosystem Diversity On Natural Enemies Of Maize Stemborers In Coastal Kenya, C. A.O. Midega, C. K.P.O. Ogol, W. A. Overholt Dec 2004

Effect Of Agroecosystem Diversity On Natural Enemies Of Maize Stemborers In Coastal Kenya, C. A.O. Midega, C. K.P.O. Ogol, W. A. Overholt

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A study was conducted at Mtwapa in the northern coastal area of Kenya during the long and short rainy seasons of 1999 and 2000 to assess the benefits of agroecosystem diversification-through agroforestry and intercropping-on the activity of natural enemies of maize stemborers. Treatments consisted of maize and cowpea intercrops or maize monocrops planted within hedgerows of Leucaena leucocephala and Gliricidia sepium. The plots were mulched or unmulched and insecticide-treated or not. The maize stemborers encountered, in order of abundance, were Chilo partellus, Chilo orichalcociliellus and Sesamia calamistis. The egg parasitoids Trichogramma spp. and Telenomus spp. were recovered from stemborer eggs. …

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Genetic Diversity In Cowpea [Vigna Unguiculata (L.) Walp.] As Revealed By Rapd Markers, Fana Sylla Ba, Remy S. Pasquet, Paul Gepts Aug 2004

Genetic Diversity In Cowpea [Vigna Unguiculata (L.) Walp.] As Revealed By Rapd Markers, Fana Sylla Ba, Remy S. Pasquet, Paul Gepts

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The present study, using RAPD analysis, was undertaken to characterize genetic variation in domesticated cowpea and its wild progenitor, as well as their relationships. The materials used consisted of 26 domesticated accessions, including accessions from each of the five cultivar-group, and 30 wild/weedy accessions, including accessions from West, East and southern Africa. A total of 28 primers generated 202 RAPD bands. One hundred and eight bands were polymorphic among the domesticated compared to 181 among wild/weedy cowpea accessions. Wild accessions were more diverse in East Africa, which is the likely area of origin of V. unguiculata var. spontanea. Var. spontanea …

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Multi-Trophic Level Interactions In A Cassava-Maize Mixed Cropping System In The Humid Tropics Of West Africa, F. Schulthess, A. Chabi-Olaye, S. Gounou Jun 2004

Multi-Trophic Level Interactions In A Cassava-Maize Mixed Cropping System In The Humid Tropics Of West Africa, F. Schulthess, A. Chabi-Olaye, S. Gounou

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Multi-trophic level interactions in a mixed crop, involving cassava and maize, were studied in derived-savanna in Benin, West Africa. Two trials were planted, one during the short rainy season two months before onset of the dry season and one during the long rainy season in spring. Key pests under study on maize were the noctuid Sesamia calamistis Hampson and the pyralids Eldana saccharina Walker and Mussidia nigrivenella Ragonot, and on cassava, the exotic mealybug, Phenacoccus manihoti Matile-Ferrero and its encyrtid parasitoid Apoanagyrus lopezi De Santis. Both crops received insecticide treatments to assess the crop loss by a pest species. On …

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Effect Of Constant Temperatures On Germination, Radial Growth And Virulence Of Metarhizium Anisopliae To Three Species Of African Tephritid Fruit Flies, Susan Dimbi, Nguya K. Maniania, Slawomir A. Lux, Jones M. Mueke Feb 2004

Effect Of Constant Temperatures On Germination, Radial Growth And Virulence Of Metarhizium Anisopliae To Three Species Of African Tephritid Fruit Flies, Susan Dimbi, Nguya K. Maniania, Slawomir A. Lux, Jones M. Mueke

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The effect of temperature on conidial germination, mycelial growth, and susceptibility of adults of three tephritid fruit flies, Ceratitis capitata (Wiedemann), C. fasciventris (Bezzi) and C. cosyra (Walker) to six isolates of Metarhizium anisopliae were studied in the laboratory. There were significant differences among the isolates in the effect of temperature on both germination and growth. Over 80% of conidia germinated at 20, 25 and 30°C, while between 26 and 67% conidia germinated at 35°C and less than 10% at 15°C within 24 hours. Radial growth was slow at 15°C and 35°C with all of the isolates. The optimum temperature …

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Crop Damage By Nematodes In Improved-Fallow Fields In Western Kenya, Serigne T. Kandji, Callistus K.P.O. Ogol, Alain Albrecht May 2003

Crop Damage By Nematodes In Improved-Fallow Fields In Western Kenya, Serigne T. Kandji, Callistus K.P.O. Ogol, Alain Albrecht

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The rotation of leguminous shrubs and crops is being tested on farms and recommended as a means of improving soil fertility and increasing crop yield in eastern and southern Africa, including western Kenya. However, this improved fallow practice may also increase the nematode population in the soil. An experiment was conducted to monitor the effects of plant-parasitic nematodes on crops after improved fallow. Soil was collected from a maize (Zea mays L.)/bean (Phaseolus vulgaris L.) field, a natural fallow, a Crotalaria (Crotalaria grahamiana Wight & Am.) fallow, a Tephrosia (Tephrosia vogelii Hook. f.) fallow and a Crotalaria - Tephrosia mixed …

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Effects Of Molasses Grass, Melinis Minutiflora Volatiles On The Foraging Behavior Of The Cereal Stemborer Parasitoid, Cotesia Sesamiae, Linnet S. Gohole, William A. Overholt, Zeyaur R. Khan, John A. Pickett, Louise E.M. Vet Mar 2003

Effects Of Molasses Grass, Melinis Minutiflora Volatiles On The Foraging Behavior Of The Cereal Stemborer Parasitoid, Cotesia Sesamiae, Linnet S. Gohole, William A. Overholt, Zeyaur R. Khan, John A. Pickett, Louise E.M. Vet

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Olfactory responses of the cereal stemborer parasitoid Cotesia sesamiae to volatiles emitted by gramineous host and nonhost plants of the stemborers were studied in a Y-tube olfactometer. The host plants were maize (Zea mays) and sorghum (Sorghum bicolor), while the nonhost plant was molasses grass (Melinis minutiflora). In single-choice tests, females of C. sesamiae chose volatiles from infested and uninfested host plants and molasses grass over volatiles from the control (soil). In dual-choice tests, the wasp preferred volatiles from infested host plants to those from uninfested host plants. There was no discrimination between molasses grass volatiles and those of uninfested …

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Screening Tomato (Lycopersicon Esculentum Mill.) Accessions For Resistance To The Twospotted Spider Mite Tetranychus Urticae Koch: Population Growth Studies, Markus Knapp, Debora Apiyo Mugada, Stephen Gaya Agong Jan 2003

Screening Tomato (Lycopersicon Esculentum Mill.) Accessions For Resistance To The Twospotted Spider Mite Tetranychus Urticae Koch: Population Growth Studies, Markus Knapp, Debora Apiyo Mugada, Stephen Gaya Agong

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The resistance of 63 tomato (Lycopersicon esculentum Mill.) accessions to the twospotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae), was investigated in screen house experiments and compared to Money Maker, a T. urticae-susceptible variety widely grown in Kenya. The number of motile mite stages 12 days after inoculation with 5 adult female mites was significantly lower than in the control variety (Money Maker) in seven accessions (Marglobe, Roma-VF, 94 RT 330, Continental Michel, Early Pearson, ARP 366-4 and 94 RT 316). Egg numbers were significantly lower than in the control in 14 accessions (Marglobe, Cal-J-VF, Roma-VF, Beauty, 95 RT 315, …

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Effects Of Different Neem Formulations On The Twospotted Spider Mite, Tetranychus Urticae Koch, On Tomato (Lycopersicon Esculentum Mill.), Markus Knapp, Sophia Shaban Kashenge Jan 2003

Effects Of Different Neem Formulations On The Twospotted Spider Mite, Tetranychus Urticae Koch, On Tomato (Lycopersicon Esculentum Mill.), Markus Knapp, Sophia Shaban Kashenge

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The effects of four different neem formulations (Neemros®, Neemroc EC®, Neemroc Combi and Saroneem) and a combination of Neemros® with a synthetic acaricide (Mitac®) on the twospotted spider mite (Tetranychus urticae Koch) were compared with Mitac® on tomato (Lycopersicon esculentum Mill.) leaf discs in the laboratory. The following LC50 were determined: Neemroc EC® 12.9 ml/l, Saroneem 5.8 ml/l, Neemroc Combi 1.0 ml/l and Mitac® + Neemros® 1 ml/l + 17.6 g/l. No LC50 was determined for Neemros® since the highest mortality observed was 11.4%. The combination of Mitac® and Neemros® resulted in the highest mortality after 24 hours (83.3%), followed …

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Isoflavanones From The Allelopathic Aqueous Root Exudate Of Desmodium Uncinatum, Muniru K. Tsanuo, Ahmed Hassanali, Antony M. Hooper, Zeyaur Khan, Festus Kaberia, John A. Pickett, Lester J. Wadhams Jan 2003

Isoflavanones From The Allelopathic Aqueous Root Exudate Of Desmodium Uncinatum, Muniru K. Tsanuo, Ahmed Hassanali, Antony M. Hooper, Zeyaur Khan, Festus Kaberia, John A. Pickett, Lester J. Wadhams

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Three isoflavanones, 5,7,2′,4′ -tetrahydroxy-6-(3-methylbut-2-enyl)isoflavanone (1), 4″,5″ -dihydro-5,2′,4′-trihydroxy-5″-isopropenylfurano-(2″, 3″;7,6)-isoflavanone (2) and 4″,5″-dihydro-2′ -methoxy-5,4′-dihydroxy-5″-isopropenylfurano-(2″,3″;7,6) -isoflavanone (3) and a previously known isoflavone 5,7,4′ -trihydroxyisoflavone [genistein (4)] were isolated and characterised spectroscopically from the root exudate of the legume Desmodium uncinatum (Jacq.) DC. We propose the names uncinanone A, B, and C for compounds 1, 2 and 3, respectively. Isolated fractions containing uncinanone B (2) induced germination of seeds from the parasitic weed Striga hermonthica (Del.) Benth. and fractions containing uncinanone C (3) moderately inhibited radical growth, the first example of a newly identified potential allelopathic mechanism to prevent S. hermonthica parasitism. © 2003 …

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Control Of Witchweed Striga Hermonthica By Intercropping With Desmodium Spp., And The Mechanism Defined As Allelopathic, Zeyaur R. Khan, Ahmed Hassanali, William Overholt, Tsanuo M. Khamis, Antony M. Hooper, John A. Pickett, Lester J. Wadhams, Christine M. Woodcock Sep 2002

Control Of Witchweed Striga Hermonthica By Intercropping With Desmodium Spp., And The Mechanism Defined As Allelopathic, Zeyaur R. Khan, Ahmed Hassanali, William Overholt, Tsanuo M. Khamis, Antony M. Hooper, John A. Pickett, Lester J. Wadhams, Christine M. Woodcock

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During investigations into the control of insect damage to maize crops in subsistence farming in Kenya, which involved intercropping with repellent plants, the fodder legumes silverleaf (Desmodium uncinatum) and greenleaf (D. intortum) were also found to reduce dramatically the infestation of maize by parasitic witchweeds such as Striga hermonthica. This effect was confirmed by further field testing and shown to be significantly greater than that observed with other legumes, e.g., cowpea, as were the concomitant yield increases. The mechanism was investigated, and although soil shading and addition of nitrogen fertilizer showed some benefits against S. hermonthica infestation, a putative allelopathic …

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