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Articles 421 - 429 of 429

Full-Text Articles in Agricultural Science

Influence Of Maize Row Spacing On Infestation And Damage Of Intercropped Beans By The Bean Aphid (Aphis Fabae Scop.). Ii. Reduction In Bean Yields, M. W. Ogenga-Latigo, C. W. Baliddawa, J. K.O. Ampofo Jan 1992

Influence Of Maize Row Spacing On Infestation And Damage Of Intercropped Beans By The Bean Aphid (Aphis Fabae Scop.). Ii. Reduction In Bean Yields, M. W. Ogenga-Latigo, C. W. Baliddawa, J. K.O. Ampofo

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Field studies were conducted to assess the effects of intercropping common beans (Phaseolus vulgaris L.) with maize (Zea mays L.), at two growth stages and four row spacings (0.5, 1.0, 1.5 and 2.0 m), on Aphis fabae infestation of beans and on the magnitudes of bean yield losses due to aphid attack and to competition by maize. The first maize planting (Old maize) was carried out 3 weeks earlier than beans, while the second planting (Young maize) was done simultaneously with beans. Significantly (P < 0.05) fewer plants were infested by A. fabae when beans were intercropped with older or densely planted maize. Aphid colonies on beans were also smaller, and there was reduced aphid damage to beans in the intercrops. However, whereas bean yield loss from aphid attack was less than 3.5% in all intercrop situations, yield loss from competition by maize was very high, being up to 98% when beans were intercropped with early-planted maize at 0.5-m row spacing. Yields of intercropped maize planted at row spacings of 0.5, 1.5 and 2.0 m were also depressed. The results show that both maize growth and row spacing could be exploited for the control of A. fabae on intercropped beans. However, adequate consideration must be given to the negative effects of maize planting density and growth on yields of both crops. © 1992.

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Larval Development Of Chilo Partellus (Swinhoe) (Lepidoptera: Pyralidae) On Artificial Diet Incorporating Leaf Tissues Of Sorghum Lines In Relation To Their Resistance Or Susceptibility, Kailash Narain Saxena Jan 1992

Larval Development Of Chilo Partellus (Swinhoe) (Lepidoptera: Pyralidae) On Artificial Diet Incorporating Leaf Tissues Of Sorghum Lines In Relation To Their Resistance Or Susceptibility, Kailash Narain Saxena

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This study was taken up to examine the relationship between the susceptibility or resistance of six sorghum lines to Chilo partellus and dietary quality of their leaf tissues, incorporated in an artificial diet, to support larval development. The diets tested were agar based basic medium with or without cellulose powder, dry leaf powder or fresh leaf-paste of the sorghum lines. The basic medium alone or with cellulose powder showed the poorest dietary quality in-as-much as it did not support more than 26–32% larval development. The tolerant sorghum IS 18520 leaf tissues, incorporated in the artificial diet as dry powder or …

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Oviposition, Larval Arrest And Establishment Of Chilo Partellus (Lepidoptera: Pyralidae) On Maize Genotypes During Anthesis, Harish Kumar Jan 1992

Oviposition, Larval Arrest And Establishment Of Chilo Partellus (Lepidoptera: Pyralidae) On Maize Genotypes During Anthesis, Harish Kumar

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The oviposition, larval arrest and establishment by the stem borer Chilo partellus (Swinhoe) were measured on different maize genotypes during anthesis. The maize genotypes tested were: Inbred A (Susceptible), Mp 704, MBR-8637, MBR-8650, MBR-8668, Poza Rica 7832, ER-29 SVR, Katumani Composite B, MMV 400, Bulk CG 4141, and ICZ2-CM. The moths oviposited on the middle leaves of the plant and the neonate larvae moved to leaf sheaths and ear husks to feed (arrest). As they grew older, the larvae invaded the stem, ear shanks and tassel to complete feeding (establishment) and to pupate. The response of the stem borer differed …

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Enhancement Of Diapause Development In A Stem Borer, Busseola Fusca (Lep.: Noctuidae) By Dry Conditions, Takashi Okuda Jan 1991

Enhancement Of Diapause Development In A Stem Borer, Busseola Fusca (Lep.: Noctuidae) By Dry Conditions, Takashi Okuda

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Water was an important factor for diapause termination only during the late stage of the diapause in Busseola fusca. Exposure to dry conditions for 2 months accelerated diapause development more. Diapause development proceeded at warm temperatures only. © 1991, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.

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Feeding Responses Of Chilo Partellus (Swinhoe) (Lepidoptera: Pyralidae) Larvae To Sorghum Plant Phenolics And Their Analogs, Baldwyn Torto, Ahmed Hassanali, Kailash N. Saxena, Sagary Nokoe Jan 1991

Feeding Responses Of Chilo Partellus (Swinhoe) (Lepidoptera: Pyralidae) Larvae To Sorghum Plant Phenolics And Their Analogs, Baldwyn Torto, Ahmed Hassanali, Kailash N. Saxena, Sagary Nokoe

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Phagostimulatory responses of third-instar larvae of Chilo Partellus to phenolic components identified in an ethyl acetate extract of the leaf whorls of 3-week-old plants of Sorghum bicolor cultivar IS 18363 were studied in no-choice bioassays. The major components in the extract were identified as 4-hydroxybenzaldehyde and 4-hydroxybenzoic acid, with 4-hydroxy-3-methoxycinnamic acid, 3,4-dihydroxycinnamic acid, and 4-hydroxycinnamic acid present in minor amounts. All but 4-hydroxycinnamic acid were stimulatory at the doses tested. 4-Hydroxybenzaldehyde was more stimulatory than other potential biogenetic analogs. Hydroxybenzoic acids generally elicited greater feeding response than cinnamic acids, and the pattern of oxygen substitution in the benzene ring was …

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Mechanisms Of Resistance In Wild Rice Oryza Brachyantha To Rice Leaffolder Cnaphalocrocis Medinalis (Guenée) (Lepidoptera: Pyralidae), R. Ramachandran, Z. R. Khan Jan 1991

Mechanisms Of Resistance In Wild Rice Oryza Brachyantha To Rice Leaffolder Cnaphalocrocis Medinalis (Guenée) (Lepidoptera: Pyralidae), R. Ramachandran, Z. R. Khan

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A wild rice, Oryza brachyantha, was rated as highly resistant to rice leaffolder, Cnaphalocrocis medinalis (Guenée), while its F1 hybrid from a cross with a high-yielding, leaffolder-susceptible rice, IR31917-45-3-2, was rated resistant in a standard screening test. In comparison with IR31917-45-3-2, O. brachyantha and the F1 hybrid were unsuitable for oviposition, survival, and growth of C. medinalis. However, growth and survival of larvae in artificial diets containing lyophilized leaf powder of IR31917-45-3-2 and O. brachyantha were comparable. Studies on the feeding and settling preference of the larval stages suggested that the mechanism of resistance of O. brachyantha is that of …

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Volatile Components Of Banana Pseudostem Of A Cultivar Susceptible To The Banana Weevil, Isaiah O. Ndiege, William J. Budenberg, Wilber Lwande, Ahmed Hassanali Jan 1991

Volatile Components Of Banana Pseudostem Of A Cultivar Susceptible To The Banana Weevil, Isaiah O. Ndiege, William J. Budenberg, Wilber Lwande, Ahmed Hassanali

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Volatiles from banana ('githumo''cultivar) pseudostem were trapped using porapak S. The trapped volatiles were desorbed from porapak columns by elution with dichloromethane and analysed using GC and GC-MS. The volatile compounds identified included α-pinene, β-pinene, β-myrcene, limonene, α-cubebene, α-copaene, α-cedrene, β-caryophyllene and α-humulene. © 1992.

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Policy Structures And Crop Productivity In Third World Countries, Zerubabel M. Nyiira Jan 1987

Policy Structures And Crop Productivity In Third World Countries, Zerubabel M. Nyiira

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Deciding what should be done in the crop-production sector is a policy issue and a public and management responsibility. Entrusted with that responsibility, governments formulate policies which should ensure maximum crop productivity. The impact of policies and policy structures on crop productivity, and the role of policy makers, administrators and scientists in research and development systems are the subjects of this paper. Observations are made on the role played by government policies in the generation, diffusion and application of crop-production technology and a brief discussion is presented of issues of public and international policies and crop productivity. © 1987.

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Influence Of The Termite Macrotermes Michaelseni (Sjöst) On Soil Fertility And Vegetation In A Semi-Arid Savannah Ecosystem, M. A. Arshad Jan 1982

Influence Of The Termite Macrotermes Michaelseni (Sjöst) On Soil Fertility And Vegetation In A Semi-Arid Savannah Ecosystem, M. A. Arshad

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The growth and species structure of vegetation in relation to the proximity of termite (M. michaelseni) mounds was studied in a semi-arid savannah ecosystem during 1978-1980. The dry matter yield in the termite-modified area at 1-10 m distance from mounds was significantly greater (P < 0.01) than that in the area beyond 22 m which is relatively unaffected by the termites. Themeda triandra and Digitaria scalarum, dominant grass species of the area, were totally absent in the 1-10 m zone around the mound. The major species in the immediate vicinity of the mound were Pennisetum stramineum and Cynodon dactylon, the latter was a dominant species (over 90%) within the 0-10 m zone and entirely absent beyond 15 m from the mound. The number of grass species increased from 2-3 species around the mound to 6-7 species in the area apparently beyond the influence of the mound. High concentration of nutrients and favourable water availability, together with good drainage, appeared to be the major causes of increased biomass and different species composition of vegetation around the mound. © 1982.

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