The Potential Use of Herbicides in Tropical Peasant Agriculture

Abstract

The possible effects of herbicide use by peasant farmers are examined. It is considered that herbicides could be used for bush clearing but that their use should not be encouraged at present. It is concluded that herbicides can be used to control perennial weeds, to protect cereal crops from witchweed and to reduce the seasonal peak of labour demand.     

The Control of Cercospora Leafspot on Groundnuts in Malawi and its Effect on the Parameters of Yield

Abstract

Leafspot is one of the major factors which limits the yield of the groundnut crop in Malawi. The most effective and economical uses of fungicidal dusts and water-based sprays to control the disease, are described. Data are also presented to show how the use of such fungicides affects parameters of yield such as numbers, size, weight and quality of kernels, and weight and quality of haulms.     

An identification guide to common whitefly pest species of the world (Homopt Aleyrodidae)

Abstract

A key is presented to aid the identification of pupal cases of 46 species of whitefly often found infesting economic plants around the world. The general pupal case morphology of each species is illustrated, together with more detailed figures of some key characters. The key is designed for use with slide‐mounted specimens, and techniques for their preparation are described. The synonymy of Bemisia hancocki with B. afer is discussed.     

Within-plant distribution of the leaf miner Tuta absoluta (Meyrick) immatures in processing tomatoes,with notes on plant phenology

Bacteria of the genus Serratia are often associated with insects, often carry distinctive pigments and can be readily isolated onto diagnostic selective media. Bacterial marking of parasitoids has been used in studies to determine rate of oviposition and host acceptance, and it provides a rapid indication of ovipositor penetration. The technique has been applied to parasitoid-weevil and parasitoid-lepidoptera interactions. Bacterial marking has the potential to be used in parasitoid dispersal studies and its use in IPM is discussed.     

A Method for Baiting Corticium rolfsii and of Estimating the Sclerotial Population in Soil

Abstract

The use of tissue blocks of Xanthosoma sagittifolim for baiting Corticium rolfsii from soil is described. The baiting technique has been found efficient for gross estimation of the viable sclerotial content of air-dried soil. The results obtained by this method compare well with those determined by the sieving technique of Rodriguez-Kabana et al.     

Presence–absence sampling for Tetranychus urticae and its predator Neoseiulus californicus (Acari: Tetranychidae; Phytoseiidae) on strawberries

The use of snails as biocontrol agents against other snails and against aquatic weeds is reviewed, evaluating their success and their impacts on non-target organisms. The predatory snail Euglandina rosea (and other species), although widely used against Achatina fulica (the giant African land snail) on Pacific and Indian Ocean islands, has not been shown to control A. fulica but has seriously impacted endemic island species. The facultative predator Rumina decollata , used in California against Helix aspersa (brown garden snail), is widely considered to be environmentally benign. However, evidence of its effectiveness is weak and it will also consume native snails. Ampullariid and thiarid freshwater snails have been used as competitors (and incidental predators) of snail vectors of human schistosomes, the parasites causing schistosomiasis (bilharzia). Successful control has been reported but impacts on native biotas have been essentially ignored. Ampullariids have been used in attempts to control aquatic weeds, sometimes successfully, but again with little consideration of impacts on native biota. Most snails have generalist feeding habits. Thus they are inappropriate biocontrol agents because of their potential nontarget effects. Rarely has adequate pre-release testing of snails been undertaken and post-release monitoring of non-target impacts has always been incidental. The use of non-native snails for biocontrol purposes is poorly regulated; many introductions are unofficial and sometimes illegal. Use of snails as biocontrol agents, if implemented, must be based on adequate pre-release testing, post-release monitoring and genuine concern for preservation of native biodiversity.     

Ecology and Control of Erinnyis ello and E. alope,Important Insect Pests in the New World

Abstract

The sphingid moth Erinnyis ello L. is an important pest of cassava and the most serious pest of the rubber tree in the New World; E. alope Drury is sometimes a serious pest of papaya. Information on the known food plants, life cycle, behaviour, natural enemies, seasonal abundance and present methods of control of these two lepidopterous pests is reviewed. The perspectives for improved control of E. ello with special reference to rubber plantations in Brazil, through the manipulation of natural enemies, a more rational use of insecticides and the adoption of certain cultural methods, are discussed.     

Weed Control in Wheat and Barley in the Middle East

Abstract

Wheat and barley constitute the bulk of agricultural production in the Middle East. Unfortunately, these crops are grown on marginal soils which are infested with annual and perennial weeds. The principal weed species include Avena sterilis L., Convolvulus arvensis L., and Sinapis arvensis L. and it has been estimated that yield losses due to weeds are between 20 and 30%. Control is mostly by hand pulling, hoeing or mechanical tillage, the use of herbicides being limited to about 2–5%, of the cereal area. The chemical used is usually 2,4-D but there are a few applications of barban. With the increase in wages, and unavailability of agricultural labour it is suggested that herbicide application should be widely used in the Middle East. Mixtures with benzonitriles and dicamba should be used in addition to the economical phenoxy herbicides to widen the spectrum of control of broadleaved weeds. Glyphosate may also be used after grain harvest for the control of perennial weeds and tri-allate, chlortoluron and other chemicals for the control of wild oats and other grasses. Plant breeders should study the genetic response of newly developed varieties to the most widely used herbicides.     

Progeny production of Steinernema abbasi in lepidopterous larvae

Progeny production of a new entomopathogenic nematode Steinernema abbasi in various lepidopterous prepupae was investigated. Most dauer juveniles (DJs) developed in the greater wax moth, Galleria mellonella (234 000) but the bollworms Helicoverpa virescens (220 000) and Spodoptera exigua (166 000) were also good hosts. Progeny production was independent of the number of nematodes invading the host between the doses of 40 and 230 DJs. The infectivity of DJs declined when they were stored for 3 months but at 30°C approximately 11% of the DJs were still infective. S. abbasi is a nematode of the semi-arid tropics and it would be possible to use the nematode to target pests in these areas if it can be produced satisfactorily locally.     

The Adaptation of a Stainless Steel Container for use as a Compression Sprayer

Abstract

Stainless steel sprayers are popular but expensive. The stainless steel tanks manufactured for use with soft drink vending machines can be adapted for use as compression sprayers relatively cheaply. The procedure and materials necessary for adapting the tank are described.     

Improving Control of the Vegetable Armyworm

Abstract

Because of recently acquired resistance of armyworm in Cyprus to prophyllactic spraying of methylparathion, a full investigation into the biology of Spodoptera littoralis was launched. It is not yet clear whether immigration to the Island occurs, but some moths can overwinter in “survival pockets” on the South coast. Pheromone traps and sterilisation are suggested as an alternative method of control. A more rational use of pesticides will cause less damage to natural enemies of the pest and reduce further development of resistance.     

Weed Control in Nigeria

Abstract

Chemical weed control is playing an increasing role in Nigerian agriculture due to the increasing cost and widespread unavailability of the labour required to carry out traditional practices. Nigeria's drive towards increased food production must involve a systematic approach to weed control based on a good understanding of weed biology and ecology. The objectives of such an approach must be the development of effective control methods which are efficient in the use of available resources and within the reach of the farmers. This paper reviews the major weed problems, the status of weed science research, and some constraints to herbicide use in Nigeria.     

Recent Advances in the Use of Plant Pathogens as Biocontrol Agents of Weeds

Abstract

Among various organisms attacking skeleton weed, Chondrilla juncea, in Europe, a rust fungus, Puccinia chondrillina, and two powdery mildews, Erysiphe cichoracearum and Leveillula taurica f. sp. chondrillae were found to be the most damaging. P. chondrillina was shown to be specific to Chondrilla and has recently been introduced into Australia where skeleton weed is important in wheat cultivation. It has already spread throughout the weed infestations and is beginning to reduce plant populations. Encouraged by the result of the Chondrilla rust, the possible use of Puccinia xanthii for the control of Xanthium strumarium and X. spinosum has also been studied. Current research on the possible use of phytopathogens in the biological control of some other weeds is reviewed.     

A review of the effects of various agronomic practices on cereal stem borer populations

Abstract

The effects of agronomic practices such as sanitation and alternate hosts, tillage and mulching, time of planting, multiple and intensive cropping, rotations, spacing, intercropping, use of fertilizers and irrigation on pest populations are reviewed, with special reference to cereal stem borers. The disadvantages of chemical control of stem borers are discussed. It is concluded that agronomic practices have some potential for reducing populations of many pest species and of increasing those of beneficial ones. The effects of cultural methods are complex, and attention is drawn to the many areas of study requiring further investigation and the need for an interdisciplinary approach.     

Chemical Control of Weeds in Cotton in the Sudan Gezira

Abstract

Early work on chemical weed control in the fallow towards the end of the Second World War is reviewed briefly. Attempts to use contact residual herbicides as pre-emergence applications in the early 1950s are also described.

Pre-sowing applications of residual herbicides were found more phytotoxic to cotton than pre-emergence applications. The closer the time of pre-sowing application to cotton sowing, the more effective was suppression of weeds competing with cotton.

Mechanical cultivations and particularly disc ploughing and rotovation to a depth of more than 15 cm were found more effective in the control of Cynodon dactylon than pre-sowing herbicide applications.

Fluometuron, noruron and prometryne were found very effective as pre-emergence herbicides. Optimum rates of application were found to be only 25-50% of rates recommended for the USA and other countries. Resistant weeds included Cyperus rotundus, Cynodon dactylon, and Rhyncosia memnonia.

A large-scale trial with fluometuron, covering 125 feddans at Wad el Nairn showed that yields obtained were equal to those with normal weeding. Costs of herbicide treatments were also comparable to costs of hand-weeding in a year of exceptionally low hand-weeding costs.     

Synthetic Pyrethroids: Their possible Role in the Control of Locusts and Leafworms

Abstract

The toxicity of a number of topically applied pyrethroids has been tested in the laboratory against three species of locusts and parathion-resistant and susceptible strains of the Egyptian cotton leafworm. Bioresmethrin, resmethrin and 5-benzyl-3-furylmethyl (+)-cis-chrysanthemate (NRDC 119) proved to be extremely active against one or more of these pests and there were small but noteworthy improvements with the synergists sesamex and TBTP. The field potential of the pyrethroids is discussed against the background of environmental problems associated with some of the insecticides in current use.     

The organisation and practice of vertebrate pest control,Elvetham Hall,Hampshire, August–September 1982

Abstract

The evaluation of an electrostatic sprayer developed by ICI, the Electrodyn® sprayer, for use in the residual treatment of dwellings for the control of malaria vectors is detailed, and the advantages of using an ultra‐low volume technique for this type of mosquito control are discussed. The impact of this new technology on malaria control programmes is also considered.     

Eldana saccharina as a Crop Pest in Ghana

Abstract

Eldana saccharina is a serious pest of maize in Ghana on the second rains crop grown in the south of the country. The question is raised whether it is worth growing a second maize crop under present conditions. E. saccharina is also a serious pest of sugarcane, causing severe losses to a valuable cash crop, and more work is needed to find suitable means of control, preferably combining the use of resistant varieties, cultural practices and natural enemies.     

Monitoring Drought in the West

Although drought is difficult to define and measure, several indices are presently available to assist in rangeland monitoring and management. Several drought indices are noted with documentation where recent information may be easily found. Temporal and spatial considerations may be helpful in management applications. Research is continuing in the development of understandable, and usable, graphical presentations of drought.     

A New Approach to Weed Control in Puerto Rican Sugarcane Fields

Abstract

Experiments have been carried out on the south coast of Puerto Rico to determine the susceptibility of Leptochloa filiformis, Echinochloa colonum and Saccharum officinarum-spontaneum-robustum hybrids (sugarcane) to various herbicides applied post-emergence.

Ametryne proved to be the most suitable herbicide for use as a selective post-emergence grass-killer in sugarcane. The crop is resistant to rates of up to 1.6 lb a.i./ac, while very young seedling grasses are highly susceptible to this or lower rates. During tillering, the weed grasses rapidly become resistant and even 3.2 lb a.i./ac (which damages emerged cane) does not kill fully tillered seedlings. The residual pre-emergence effect of ametryne applied over seedling grasses is as pronounced as when this herbicide is applied to clean ground.