摘要:

A survey of rice insect pests conducted during 1983–87 in Nigeria revealed 70 species of pests, 14 parasitoids and two predators. Both incidence and severity of pests varied considerably across different climatic zones and rice agro‐ecosystems. Thirteen Insects were classified as major pests. They are: stalk‐eyed fly.Diopsis longicornisMacquart; lepidopterous stem borers.Mallarpha separatellaRag.,Chllo zacconiusBlesz,Sesamiaspp.; African gall midge,Orseolia oryzivoraH&G;armyworm,Spodopteraspp.; leaf folder,Marasmia trapezallsGuenée; grain‐sucking bugs.Asparvia armlgeraFab.,Stenocorisspp.; case worm,Nymphula stagnalisZell; lady bird beetle,Epilachna similisThunb.; whorl maggot,Hydrellia prosternalisR&D; and termites. The brown plant hopper,Nilaparvata maeanderFennah, and whitefly,Aleurocybotus indicus D&Sare potentially serious pests. The insect pest situation will probably change in Nigeria as the use of modern inputs increases, based on experience In Asia.

ISSN:0143-6147    

DOI:10.1080/09670879209371666

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The results of field experiments showed that an improved crop package caused considerable reduction in density and dry weights of all categories of weeds and increased yield four times over traditional farmers’ practices in rainfed upland rice. Better land preparation (two ploughings at 15 d.b.s. and two at sowing), timely sowing (last week of June), application of fertilizer and an additional hand weeding markedly decreased the infestation of all categories of weeds in rainfed upland rice and helped in producing high grain yield. Improved variety and organic manuring had no effect on weed infestation but seemed to be essential for the yield improvement of upland rice.

ISSN:0143-6147    

DOI:10.1080/09670879209371667

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Transmission of okra leaf curl virus by seed or by mechanical inoculation was not demonstrated. Transmission by the whitefly vectorBemisia tabaciGenn. from okra to okra was successful but not from okra to cassava orN. benthamiana.The disease was more prevalent in the savannah area in the north of Côte d'lvoire than in the forest area to the south. The spatial distribution of infected plants and the whitefly vector led to gradients downwind from sources of infection.

ISSN:0143-6147    

DOI:10.1080/09670879209371668

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Isolation of fungi from samples ofOrobanche crenataForsk. andOrobanche minorSm. plants collected from Syria, Morocco, and France yielded 16 different species belonging to nine genera. The most common genera wereAlternaria, FusarlumandUlocladium.Eleven species out of the 16 had not been known previously to have occurred onOrobanche.In the preliminary laboratory and field testsUlocladium atrumPreuss. could infect and destroy underground tubercles and emerged shoots ofO. crenataprovided temperature was around 20°C and the relative humidity between 50% and 80%. Its use as a potential biological control ofOrobancheappears promising and should, therefore, be further studied.

ISSN:0143-6147    

DOI:10.1080/09670879209371669

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Field trials were conducted on the farm of the Institute for Agricultural Research, Samaru, Nigeria, during the 1985 and 1986 rainy seasons (May‐October) to evaluate herbicide treatments for weed control in the Simultaneous system of farming with sorghum—groundnut mixtures. Most of the low rates of herbicide treatments followed by supplementary hoe‐weeding (SHW) reduced weed infestation better than the higher rates without hoe‐weeding, but comparably to the twice hoe‐weeded control. Propachlor plus terbutryne at 2.0 + 1.0 kg a.i./ha, followed by SHW, was found to be promising in terms of selectivity in the component crops, with season‐long weed control, and to improve both sorghum and groundnut yield, which are comparable to the hoe‐weeded control. Pree (Metazachlor with ‘antidote') plus terbutryne at 0.5 + 1.0 and 0.75 + 1.0 kg a.i./ha, with and without SHW, respectively, although effectively reducing weed infestation and improving groundnut yield in 1985, produced high pod yield in 1986 only in plots treated with the low rate followed by SHW; moreover it was found to be phytotoxic to sorghum establishment and growth, which resulted in reduced grain yield. In these trials SHW was therefore found to be very important for an effective season‐long weed control.

ISSN:0143-6147    

DOI:10.1080/09670879209371670

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The within‐tree distribution of the guava fruit fly,Anastrepha striatain sour guava,Psidium friedrichsthalianumand common guava,P. guajavain the seasonal highlands and non‐seasonal lowlands of Costa Rica, was examined in relation to host fruit distribution, temperature, and ambient light levels. Larvae and adult flies were significantly more abundant in the middle and lower parts of trees than in the upper canopy layer where temperatures inside sun‐exposed, potential host fruits reached lethal levels for eggs and larvae ofA. striata.The number of adult flies was also significantly greater in relatively compact foliage than in fairly open foliage of host trees. The results suggest that the foliage structure of host trees, through its influences on the temperature inside host fruits, is determining the within‐tree distribution ofAnastrephafruit flies.

ISSN:0143-6147    

DOI:10.1080/09670879209371671

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Field incidence of a virus disease of zucchini squash causing severe mosaic, vein banding, shoe stringing, distortion of leaves and fruits with occasional blisters was monitored during 1988–1990 at 12 locations in four districts of Nepal. The causal agent was transmitted by sap and aphids but was not seed‐borne. Electron microscopic observation of samples collected from infected plants revealed flexuous elongate particles resembling those of potyviruses. Based on these results, the causal virus was tentatively diagnosed as zucchini yellow mosaic virus. In field plantings the onset of the disease was earlier and spread occurred more rapidly in March and April plantings than in one made in January. Spread was more than 8.5% per day during both pre‐ and post‐monsoon seasons. The disease significantly reduced various yield attributes. The disease was epidemic in most farmers’ fields at low elevations (about 250 m) and much less at higher altitudes (>1500 m).

ISSN:0143-6147    

DOI:10.1080/09670879209371672

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The anthurium whitefly,Aleurotulus anthuricolaNakahara, completed its life cycle within the inner surface of anthurium sheaths. The entire life cycle from egg to adult was 35.5 ± 1.2 days. Tests indicated that systemic insecticides were more effective than contact insecticides. Under greenhouse conditions the systemic insecticides, methomyl 1.8 L and dimethoate 4.0 EC, significantly reduced eggs, nymphs, pupae, and adult whiteflies. The contact synthetic pyrethroid, fenpropathrin, 2.4 EC, also reduced all stages of the whitefly but was not as effective as the systemic insecticides. The contact insecticides, malathion, 5.0 EC was only effective against adult and pupal stages and bifenthrin 10 WP was effective only against the adult stage of the whitefly. In field trials, methomyl 1.8 L and acephate 75 SP, both systemic insecticides, significantly reduced nymphs and pupal stages of the whitefly. Eggs were also significantly reduced in acephate 75 SP‐treated plots.

ISSN:0143-6147    

DOI:10.1080/09670879209371673

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Cylindrocladium clavatumcauses damping‐off and root rot of Eucalyptus whileC. scopariumalso produces serious leaf spot and leaf blight in addition to root rot. This paper reports results of comparing the damping‐off ability of the two fungi. Forty‐one provenances belonging to 17Eucalyptusspp. and oneMelaleucasp. were screened in growth chambers for resistance to damping‐off byC. clavatumorC. scoparium.Provenances ofE. torellianaE.citridodora, E. degluptaandE. maculatawere resistant to bothCylindrocladiumspp. Six provenances of five species (E.robusta, E. resinifera, E. urophylla, E. citriodoraandE. grandis)were resistant only toC. scoparium.Eleven other provenances belonging to eight species (E.grandis, E. pellita, E. urophylla, E. pilularis, E. pellita, E. camaldulensis, E. pellita, E. resinifera, E. grandisand E. maculata) were moderately resistant toC. clavatumbut only eight provenances belonging to six species (E.deanei, E. grandis, E. pellita, E. saligna, E. urophyllaand E.pilularis)were moderately resistant toC. scoparium. C. clavatumwas more aggressive thanC. scopariumtowards mostEucalyptusspp. besides having a wider host range thanC. scopariumamongEucalyptusspp.Melaleucasp. was susceptible to both fungi.

ISSN:0143-6147    

DOI:10.1080/09670879209371674

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Cashew production in Tanzania has declined dramatically since the mid‐1970s. Changes in socioeconomic factors have Influenced this, but previous work has shown that cashew tree yields have been substantially reduced by the occurrence of powdery mildew caused byOidium anacardii.This disease was first recorded from Africa in 1979 and is an apparently new introduction. Most of the cashew tree population in Tanzania appears to be susceptible to the disease, which has its most severe effect on the inflorescence and prevents fruit set. Characteristics of the cashew powdery mildew pathosystem are reviewed, and control strategies based on the use of fungicides and host plant resistance are discussed.

ISSN:0143-6147    

DOI:10.1080/09670879209371675

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor