摘要:

The relationship between the concentration of phenol in cowpea and field resistance to the legume pod borer,Maruca testulaliswas determined in variably resistant cultivars. Phenol concentration varied significantly (P<0.05) between the different parts of the cultivars at the same growth stage, and generally decreased with increase in plant age. Despite the differences in phenol concentration between cultivars, correlations showed that phenol does not play any significant role in cowpea resistance toM. testulalis.

ISSN:0967-0874    

DOI:10.1080/09670879309371802

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Intercropping studies conducted at the International Centre of Insect Physiology and Ecology (ICIPE) for 10 years identified sorghum and cowpea as the best crop combination in terms of minimizing crop borer population, stabilizing productivity and reducing yield loss due to crop borers. The maize and cowpea dicrop and the sorghum, cowpea and maize intercrop were also found to be effective. The worst crop combination was found to be an intercrop between maize and sorghum. It was also indicated that incorporation of resistant and tolerant cultivars in an intercropping system offers an added advantage (by reducing the pest attack) to farmers who for some very good reasons had to plant the maize and sorghum dicrop (the worst combination). The use of resistant and tolerant cultivars therefore offers an alternative. In the study further observations were noted from three combinations, viz. resistant/resistant; resistant/susceptible; and susceptible/susceptible. Results showed that there were no significant differences between resistant and resistant/ susceptible combinations, suggesting the possibility of intercropping resistant and susceptible plants within a monoculture of multi‐line intercropping. This finding opened up a new chapter in cropping systems in the sense that intercropping was seen as a practice that would also benefit large‐scale farmers.

ISSN:0967-0874    

DOI:10.1080/09670879309371803

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The accession ofOryza glaberrima(IRGC Acc. no. 100139) was identified and evaluated as an indicator plant for rice tungro spherical virus (RTSV), a latent virus of rice. This accession was susceptible and sensitive to RTSV infection. When 7‐day‐old seedlings were inoculated with viruliferous leafhopperNephotettix virescensthe infected plants showed stunting, reduced tillering, and pale green leaves 3–4 weeks after inoculation. The visual evaluation of infected plants corresponded well with the serological assay. Accession 100139 could also be used to distinguish plants infected either with rice tungro bacilliform virus (RTBV) or both RTBV and RTSV, based on characteristic symptoms and the life span of infected plants. The indicator plant would be useful in studying the epidemiology of rice tungro viruses without the need for expensive serological assays

ISSN:0967-0874    

DOI:10.1080/09670879309371804

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper describes both the colonization process and a method for estimating popular size inHylesinus variusa scolytid pest of various plant species including ash and olive. The colonization process occurs in two phases; during the first phase the construction of maternal feeding galleries induces a response by the tree which leads to the appearance of tumerous thickenings of the bark (so‐called ‘roses'); in the second phase further feeding galleries are constructed in the same roses and also at new sites on the tree. Population size in the olive grove (100 ha) was estimated to be 147700 adults, with a 1:1 sex ratio. The results obtained in this work are considered essential for the study of the dynamics of theH. variuspopulation and for developing optimal control of the pest.

ISSN:0967-0874    

DOI:10.1080/09670879309371805

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The fate and residues of pesticides in a rice paddy ecosystem were monitored because this is suspected to contribute more to pesticide pollution than any agroecosystem in the tropics. High pesticide user and low pesticide user farmers were selected in rice‐growing areas for two cropping seasons. In chlorpyrifos‐treated rice fields residues in paddy soil and water remained longer in the high pesticide user's farm than in the low pesticide user's farm. Monocrotophos residues in soil and water remained longer in the supervised field than in the farmer's field. Monocrotophos and chlorpyrifos residues in the immediate atmosphere did not exceed the threshold‐ level value (TLV) of 0.2 mg/m3of air. Pesticide residues on test animals were within the maximum residue limit (MRL) set by FAO/WHO.

ISSN:0967-0874    

DOI:10.1080/09670879309371806

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Studies were conducted to examine the possibility of using entomogenous fungi to control the diamondback moth (DBM),Plutella xylostellain Serdang, Selangor, Malaysia. Results from mass‐culturing indicated that rice was most suitable for growth and sporulation amongst the loose‐solid media tested and coconut water for the liquid media. Three applications of spore suspensions ofBeauveria bassianaandPaecilomyces fumosoroseuseach applied at a dilution of 1 χ 108spores/ml at a rate of 3.75 χ 1013spores/ha were required to cause significant reduction (?<·05) in the larval population of DBM. Sprays of permethrin (·025%) on plants already treated withB. bassianashowed no added improvement to the protection of the cabbage leaves. Alternating sprays of cypermethrin (0.01%) and phenthoate (0.1%) did not significantly increase the yield of marketable cabbage heads when compared with plots treated with the entomopathogens. The virulence of both fungal species was maintained throughout the duration of the experiment

ISSN:0967-0874    

DOI:10.1080/09670879309371807

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Seven near‐isogenic lines of rice were evaluated in the glasshouse for resistance to Nepalese strains ofXanthomonas oryzaepv.oryzaethe causative agent of bacterial blight in rice. Lesion length at 14 days after clip inoculation was used to characterize resistance or susceptibility of near‐isogenic rice lines to the 25 strains ofX. o.pv.oryzae.Considerable variation In reactions among near‐isogenic rice lines was observed. IR‐BB3 was highly susceptible to more than 80% ofX. o.pv.oryzaestrains, while IR‐BB1, IR‐BB7, and IR‐BB11 were resistant to one‐third of the strains. IR‐BB4 and IR‐BB5 were moderately to highly resistant to nearly 50% of the strains. IR‐BB8 exhibited a high level of resistance to nearly two‐thirds of the strains ofX. o.pv.oryzaethat were evaluated. No specificity of infection was observed, suggesting that these near‐isogenic lines are of little value in discriminating amongst pathogenic races ofX. o.pv.oryzaein Nepal.

ISSN:0967-0874    

DOI:10.1080/09670879309371808

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A survey was conducted in farmers’ fields in Nigeria during the 1990 cropping season to determine the prevalence of sorghum diseases in the four major sorghum‐growing climatic zones (Sahel, Sudan, northern Guinea, and southern Guinea). The foliar diseases anthracnose(Colletotrichum graminicola)oval leaf spot(Ramulispora sorghicola)sooty stripe(Ramulispora sorghi)and grey leaf spot(Cercospora sorghi)were widely distributed. Anthracnose was predominant throughout the areas surveyed with ≥40% leaf area covered or destroyed by lesions in 70% of the surveyed fields. The incidence of other foliar diseases was low. Among the panicle diseases, long smut(Tolyposporium ehrenbergii)incidence was ≤10% in ≥20% farmers’ fields in the sahelian zone. Head(Sporisorium reilianum)covered(Sporisorium sorghi)and loose(Sphacelotheca cruenta)smuts were common, but their incidence varied from 1 to 10% in the Sahel, Sudan, northern Guinea and southern Guinea zones. Survey results based on ELISA indicated for the first time in Nigeria the presence of three virus diseases of sorghum: maize mosaic (maize mosaic virus), maize stripe (maize stripe virus), and a potyvirus in the Sudan, northern Guinea, and southern Guinea zones. Grain moulds, charcoal rot(Macrophomina phaseolina)and bacterial diseases were not observed during this survey.

ISSN:0967-0874    

DOI:10.1080/09670879309371809

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In a field experiment the role of three crop rotations: brinjal‐radish‐onion‐brinjal, tomato‐wheat‐maize‐brinjal and tomato‐onion‐resistant tomato‐okra for the management of root‐knot nematode,Meloidogyne javanicawas investigated. Radish, wheat, maize, onion and resistant tomato tended to decreaseM. javanicapopulations by different amounts; brinjal favoured maximum multiplication of the nematode. Tomato‐onion—resistant tomato—okra was found to be the best rotation for limiting the root‐knot nematode population and in bringing the highest net returns (Rs. 54687/ha). Maize supported large numbers ofTylenchorhynchus goffartiandHoplolaimus indicus.

ISSN:0967-0874    

DOI:10.1080/09670879309371810

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In an investigation into the response of cassava yield to different planting dates, two local cultivars (red‐ and white‐skinned) were planted on eight dates from March to October, corresponding to the wet period of the zone, from 1984 to 1986. Fresh storage root yields were evaluated 12 months after planting with the incidence and severity of the main diseases. The fresh storage root yield 12 months after planting increased from March to August plantings and began to decrease from September in both cultivars. The white‐skinned cultivar was superior to the red‐skinned with a mean yield difference of 5–0 t/ha and mean storage root number of 9.5 per 10 m2. Fresh storage root yield of both cultivars followed the same rainfall pattern but the reverse was recorded in relation to sunshine hours. Early planting produces greater marketable yields. Cassava mosaic, bacterial blight and leaf spot diseases decreased from the early to the late plantings in both cultivars. Cassava can give profitable yields if planted from March to October in the area studied. If larger roots are preferred, early planting is recommended; late planting is recommended for quality leaves devoid of disease. The choice of planting period depends on the needs of the farmer for fresh storage root, the time available and the inputs at his disposal.

ISSN:0967-0874    

DOI:10.1080/09670879309371811

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor