摘要:

In a survey conducted in the four major rice ecological zones in Nigeria the predominant weeds of the flora growing in association with both direct‐seeded and transplanted rice(Oryza sativaL.) were determined. Most of the predominant weed species differed with differing rice ecologies. Among the predominant broadleaved species,Ageratum conyzoidesL.,Sphenochlea zeylanicaGaertn,Tridax procumbensL.,Portulaca oleraceaL. andCelosia argenteaL. were each found common to two different ecologies. Also, each of the grass species, includingOryza longistaminataChev and Roehr,Eleusine indica(L.) Gaertn,Digitaria sanguinalis(L.) Scop,Panicum maximumJacq andPanicum repensL. were found in two different ecologies. Of the sedge species,Cyperus rotundusL,Cyperus imbricatusL.,Cyperus difformisL. andFimbristylis dichotoma(L.) Vahl were each found in two different ecologies. The predominant weed species and their relative importance varied with the varying rice ecologies. There was little similarity between the weed communities, indicating that weed species are highly selective in adaptation. Recommending a single herbicide for all the rice ecologies would therefore be most undesirable. The predominant weed species in the various rice ecologies represent potential problems for the present and the future.

ISSN:0143-6147    

DOI:10.1080/09670878609371075

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Field trials were carriedoutduring winter seasons of 1981–82 and 1982–83 to assess the efficacy of the herbicide chlortoluron and hand weeding in controlling weeds in opium poppy at the Rajasthan College of Agriculture, Udaipur. Application of Chlortoluron at 1.5 kg/ha resulted in high yield of opium latex and seed and low weed count and weed dry matter yield at harvest, compared with the effect of hand weedings after 20, 40 and 60 days.

ISSN:0143-6147    

DOI:10.1080/09670878609371076

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A study to assess the economic and technical feasibility of chemical weed control method in maize (Zea maysL.) production was conducted during 1981 to 1983 cropping seasons. The results indicated that the use of herbicide reduced time required for hoe‐weeding, delayed hoe‐weeding and consequently reduced the labour demand during the months of June to August by 38%. A better weed control achieved on the herbicide‐treated plots resulted in yield increases of 9%, 6% and 15% per ha in 1981, 1982 and 1983, respectively, compared with the control plots. Based on income returns and labour use per ha, herbicide technology was found superior to hoe‐weeding alone.

ISSN:0143-6147    

DOI:10.1080/09670878609371077

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Colletotrichum gloeosporioideswas identified as the causal agent of carrot umbel blight in Brazil. Pathogenicity was evaluated on carrot and other host plants, as well as compared with the pathogenicity of otherC. gloeosporioidesisolates on carrot.C. gloeosporioidesisolated from carrot umbel was able to infect tomato plants and ripe fruits of tomato and sweet pepper, in addition to carrot umbels and seedlings. This appears to be the first report ofC. gloeosporioidesattacking carrots.

ISSN:0143-6147    

DOI:10.1080/09670878609371078

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Anthracnose development was not influenced by different plant population. Yield loss of marketable fruits was 99–5%. Carbendazim and benomyl applications had decreased disease intensity, increased yield and decreased infection rates. Carbendazim, benomyl and captafol had reduced the basic infection rate R values to 1:18, 1:10 and 1:4, respectively. Correlations between the disease indices and marketable and total fruits were negative, while with the diseased fruit numbers were positive. Bottlegourd anthracnose epidemic progressed as a polycyclic disease.

ISSN:0143-6147    

DOI:10.1080/09670878609371079

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Corynespora cassiicolais reported in the Republic of Seychelles, where it causes a leaf spot disease of tomatoes, cucumbers and watermelons. Isolates from tomatoes and cucumbers were cross pathogenic, but differences in symptoms indicated a degree of host specificity. The fungus developed rapidly as a saprophyte and sporulated abundantly for at least 28 days on dead tomato leaves in the field. Numbers of conidia increased with duration of wetting of the debris.C. cassiicolacolonized and sporulated on papaya leaf debris. Isolates from papaya leaf debris caused leaf lesionsontomato, cucumber and watermelon, but isolates pathogenic on papaya were not found.C. cassiicolais an aggressive facultative parasite that sporulates abundantly on plant debris. Inoculum ofC. cassiicolafrom several sources can initiate disease cycles. Consequently, sanitation as a control measure appears to be justified.

ISSN:0143-6147    

DOI:10.1080/09670878609371080

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Angular leaf spot of beans caused byPhaeoisariopsis griseolais a major problem on this crop in Eastern Africa. The sources of inoculum for this disease were investigated. The causal fungus was confirmed as seedborne in all the cultivars tested. The fungus caused seed discolouration but not all infected seeds were discoloured. Seed to seedling transmission was low. The fungus survived in infected crop debris for a maximum of nine and four to six months under indoor and outside conditions respectively. Under soil, the fungus survived for only two months. Infected offseason crops and volunteer plants were present at the time of planting the seasons’ crops and were an obvious source of the inoculum. It is concluded that the seed, crop debris, off‐season crops and volunteer plants are all possible sources ofP. griseolainfection under the local conditions.

ISSN:0143-6147    

DOI:10.1080/09670878609371081

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Puccinia psidiicauses rust on neotropical Myrtaceae and exoticEucalyptusspp.. Serious losses have been detected in Brazilian plantations of Eucalyptus. In the present work 27 provenances of 12Eucalyptusspecies were screened for resistance toP. psidiipresent in the southern part of the State of Bahia, Brazil. Provenances ofEucalyptus pellita, E. urophyllaEtereticornis, E. resiniferaEcamaldulensis, E.citriodora, E.microcorysandE.paniculatashowed resistance to the population ofP. psidiifrom South Bahia. Highly susceptible materials were detected among provenances ofE.grandisandE.cloeziana.These results differed from previous observations in the neighbouring State of Minas Gerais. This suggests differences in pathogenic behaviour of the populations ofP.psidiifrom those two areas.

ISSN:0143-6147    

DOI:10.1080/09670878609371082

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

South American leaf blight (SALB) caused by the fungusMicrocyclus ulei(P. Henn.) v.Arx is the main limiting factor to the development of the natural rubber (Heveabrasiliensis)industry in South and Central America. It also poses a great danger to the rubber grown extensively in Africa and South‐east Asia. Present knowledge of its distribution, epidemiology and spore viability, the risks of its entry into Asia and Africa and its possible behaviour in these countries are reviewed. In the control of this devastating disease, application of defoliants and fungicides, breeding for leaf blight resistance and crown budding of high yielding susceptible panel clones with leaf blight‐resistant crowns are measures currently being investigated. Present quarantine regulations appear inadequate. The need for more rigorous measures are stressed.

ISSN:0143-6147    

DOI:10.1080/09670878609371083

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0143-6147    

DOI:10.1080/09670878609371084

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor