摘要:

Trials described show that control of the secondary spread of groundnut rosette virus, which is transmitted byAphis craccivoraKoch, is possible with insecticides. In six trials carried out in the period 1965–1970 insecticides tested included dimethoate, phosphamidon and dicrotophos as emulsion concentrates and ulv formulations, menazon as a wettable powder, endosulfan and phenthoate as an emulsion concentrate and aldicarb as a granular formulation. Menazon, at a rate of 294 g a.i./ha applied four times at ten day intervals starting ten days from the germination (emergence) of the crop, was the most efficient insecticide overall in reducing rosette attack. In two trials it was shown to be very effective at rates of 196 and 147 g a.i./ha. Endosulfan and dimethoate and to a lesser extent phosphamidon were also successful as emulsion concentrates and in the instance of dimethoate and phosphamidon as ulv's. Dicrotophos was promising in the two trials in which it was used, but phenthoate was not. Aldicarb, used as a side dressing, was inadequately tested. Ulv application was quick, simple and efficient and has much to recommend it in Uganda conditions. Insecticides significantly reduced the percentage plants attacked in growth up to harvest. There were improvements in kernel quality, shelling percentage and yield. It was concluded that in most seasons even on well grown and well tended crops spraying was worthwhile.

ISSN:0030-7793    

DOI:10.1080/09670877509411481

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

In Uganda, robusta coffee, which forms the main crop, is relatively free from pests, but these can be serious with the more valuable arabica crop. Most research in the last 20 years has been directed towards the development of chemical control methods and of machinery suitable for use by smallholders. Of insecticides tested, fenitrothion has been found suitable for controlling most coffee pests. Its application is a problem since most of the coffee is not accessible to wheeled machinery, and farmers cannot afford expensive sprayers. Teams using knapsack sprayers have been found suitable for the routine treatment of arabica coffee. Any applications to robusta coffee are made by individual farmers. Recommended threshold levels for spraying are given for some insects. Experience has shown that insecticide applications can create new pest problems. The ecology of coffee pests in Uganda requires more study since little is known of the causes of outbreaks or why pests differ in importance locally.

ISSN:0030-7793    

DOI:10.1080/09670877509411482

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The effectiveness and economics of two commonly recommended methods of reducing rat damage to coconuts were examined.

ISSN:0030-7793    

DOI:10.1080/09670877509411483

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Bacterial wilt of cassava has been causing a severe reduction of tuber yield in the savanna of the southern part of Zaire since 1970. Infection of young shoots often takes place through insect punctures made mainly byPseudotheraptus devastansDistant. Systemic colonisation of the stem leads to vascular browning, formation of bacterial pockets in the bark which extrude a yellow-white exudate and sudden drying of the leaves and necrosis of the stem tips. Angular leaf spots, accompanied by small droplets of exudate on the lower surface of the lesion, rapid blight of large areas of the lamina and defoliation, are endemic in Zaire. Epidemics develop under conditions of heavy rainfall. The cultural appearance, the morphological and biochemical characters as well as the cross-inoculation tests demonstrate that the bacteria causing wilt, leaf spotting and blight are identical. They are identified asXanthomonas manihotis(Arthaud-Berthet) Starr and can be distinguished from a Brazilian isolate ofX. manihotisonly by a lower amylolytic activity. A critical analysis of the literature suggests a worldwide distribution of the disease. The recent epidemic development of bacterial wilt in Zaire and the control by resistant cultivars are discussed.

ISSN:0030-7793    

DOI:10.1080/09670877509411484

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Bacterial blight of cassava is a serious problem in Central and South America and has been observed in parts of Africa. Symptoms include leaf spotting, wilting, die-back, gum exudation on young shoots, and vascular discoloration in mature stems and roots of susceptible cultivars. Dispersal by rain splashing is the most important means of dissemination within localized areas. Dissemination from one area to another occurs through infected planting material or by the use of contaminated tools. Delay in spread of the disease has been obtained by pruning infected plants. The use of resistant varieties and the production of certified bacteria-free planting material, obtained from plants propagated from shoot tip cuttings, has given satisfactory control.

ISSN:0030-7793    

DOI:10.1080/09670877509411485

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Recent developments on the identities of the causal agents of bacterial diseases of cassava throughout the world are discussed.

ISSN:0030-7793    

DOI:10.1080/09670877509411486

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Taro cultivation in the Solomon Islands is in decline because of severe disease and insect problems. Fungal diseases, the most important of which is leaf blight caused byPhytophthora colocasiaeRac, result in considerable crop losses.Pythiumspp. andErwinia chrysanthemlBurkholder, McFadden Dimock cause rotting of roots and corms. Several pathogens affect stored corms. Resistance to virus diseases, which are transmitted by the delphacidTarophagus proserpina(Kirk.), varies according to cultivar. The most serious insect pest is the taro beetlePapuans inermisPrell. Other insects usually cause only minor damage. Control measures and current research at the Dala Research Station on taro insect and disease problems are discussed.

ISSN:0030-7793    

DOI:10.1080/09670877509411487

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The effects of weed competition on cassava yield were assessed using two sets of treatments. In the first set, plots were kept weed free for specified periods and then weeds were allowed to grow. In the second set, weeds were allowed to grow initially for specified periods and were then eradicated. Effects were assessed from fresh weights of cassava roots, and weed species commonly found in the plots were identified. The work was done in the rain forest zone of western Nigeria. The predominant weed species were mainly annual broad-leaved species and competition from weeds at any period of growth after rooting reduced yield. The most damaging effect on yield was noted during early canopy formation and early tuberisation (third month after planting) and a less damaging effect from the fourth month until harvest. Where labour is a limiting factor in cassava production labour input should be applied during the third month after planting to control weed growth. Weeding during this period was as effective in ensuring a high yield of cassava roots than weeding throughout the entire period of growth.

ISSN:0030-7793    

DOI:10.1080/09670877509411488

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Repeated applications of glyphosate, formulated as MON-2139, were tested against persistent perennial sedges, grasses and broad-leaved weeds of coffee in Kenya. The possibility of eradicating these weed species by applying dosage rates of 2,4 or 6 kg a.e./ha towards the beginning of the rains, followed three months later by the same or half the dosage rate, was studied. Undirected sprays appeared very potent against all the species under test, but caused injury to coffee suckers.

ISSN:0030-7793    

DOI:10.1080/09670877509411489

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Orobanche is the most debilitating plant parasite of tobacco in Andhra Pradesh. The crop suffers considerably for about six weeks before the parasite appears above the ground. In the absence of effective herbicides for controlling Orobanche especially in this pre-emergence phase, it was felt worthwhile to evaluate the effectiveness of various cultivated crops as trap crops. A preliminary pot trial was conducted with 17 crop plants and the results are presented.

ISSN:0030-7793    

DOI:10.1080/09670877509411490

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor