摘要:

Yield reduction of cassava infected with African cassava mosaic virus (ACMV) was greater when plants were infected from the outset as cuttings than later by the whitefly vectorBemisia tabacl.Early infection byB. tabacicaused greater losses than late infection. When symptoms first appeared, more than four months after planting, there was no significant yield reduction. Yield reductions in plots where diseased plants were inter‐mixed with healthy ones and subject to inter‐plant competition were much greater than when they were assessed using separate healthy and infected plots. Crop losses due to ACMV in the cultiver CB were estimated atca40%.

ISSN:0143-6147    

DOI:10.1080/09670878809371216

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Re‐infection of healthy cassava plants by African cassava mosaic virus (ACMV) was followed In different varieties and for several years at various locations in two regions of Ivory Coast. Whitefly populations on cassava and virus incidence varied widely between sites, even amongst those close to one another. However, for each location and in every year, the spread of ACMV showed the same general trend. Little spread occurred at Toumodi in the savannah region which is outside the main cassava production area. Much greater spread occurred at a nearby site and at all sites in the forest region except one alongside the ocean where there were no cassava plantings upwind. Among sites there was no direct relation between virus incidence and the total number of adult whitefly, whereas there was a relationship between spread and the occurrence of infected cassava upwind although not necessarily close by.

ISSN:0143-6147    

DOI:10.1080/09670878809371217

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Studies were carried out on farms to evaluate potential control practices which could be constituted into a package of recommendations for the control ofStriga hermonthicain the Gambia. ICSV 1002, a variety of sorghum, was identified as being relatively more tolerant toStrigaand to the common insect pests of sorghum. Spot treatment of emergedStrigashoots with 2% solution of product paraquat using a pistol‐grip hand sprayer was found to controlStrigawithout stimulating regrowth, improved yields and was more acceptable and cost‐effective than handpulling of the shoots in early millet and sorghum. Where there might be objections to the use of paraquat because of its toxicity hazards, a mixture of 2,4‐D (1 % soln.) plus glyphosate (1 % soln.) or 2,4‐D (2% soln.) was a useful substitute. A tentative control package consisting of ICSV 1002, spot spraying ofStrigashoots with paraquat, and side dressing of urea fertilizer at 30 kg N/ha at 4 w.a.p. was tested at two sites against farmers’ practice on pilot scale. Infestation ofStrigawas reduced and yields were increased by 119% and 37% by the package at the two sites.

ISSN:0143-6147    

DOI:10.1080/09670878809371218

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A field experiment was conducted during the wet seasons of 1980 and 1981 to find out the relative influence of weed control and applied nitrogen on performance of transplanted rice and nutrients uptake by rice and weeds. Propanil and thiobencarb, each at 2.0 kg a.i/ha, were found comparable to two hand weedings in increasing grain yield of rice and minimizing dry matter of weeds. The mean grain yield was increased by 28.06% while dry matter of weeds reduced by 84.04% over unweeded control. Application of nitrogen from 0 to 75 kg N/ha increased grain yield to the tune of 1631 kg/ha. Remarkable increase in grain yield was noticed when weed control treatments were associated with application of nitrogen. Higher uptake of N, P and K by crop and lower removal of same nutrients by weeds were observed in herbicides and hand weedings than unweeded control. N, P and K in the order of 11.49, 1.71 and 12.40 kg/ha respectively could be saved through weed control in transplanted rice.

ISSN:0143-6147    

DOI:10.1080/09670878809371219

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0143-6147    

DOI:10.1080/09670878809371220

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

During August 1986 when there was a build up ofParasa lepidaCramer on coconut in the study area in Kerala, India, many dead larvae were found on the underside of the leaves. A few of these cadavers which were suspected to be infected by a virus were collected. Pathogenicity tests proved positive. PIBs were negative to stain by Giemsa, and section of the polyhedra shows that the virions are rod shaped. The pathogen is a multiple embedded baculovirus.

ISSN:0143-6147    

DOI:10.1080/09670878809371221

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0143-6147    

DOI:10.1080/09670878809371222

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0143-6147    

DOI:10.1080/09670878809371223

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0143-6147    

DOI:10.1080/09670878809371224

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0143-6147    

DOI:10.1080/09670878809371195

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor