ISSN:0967-0874    

DOI:10.1080/09670879309371750

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The complexities of managing migratory insect pests are reviewed. The roles of forecasting and preventive management strategies are discussed and illustrated from a variety of taxa and geographical areas, emphasizing the need to understand the effects of weather on migration. The potential of preventive management has not been exploited widely, partly through ignorance of the migratory ability of many insect pest species, and partly through the difficulties of founding and maintaining the operational organizations.

ISSN:0967-0874    

DOI:10.1080/09670879309371751

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Several native grasses, sorghum lines and maize genotypes were tested for susceptibility toPeronosclerospora sorghi(Weston and Uppal) C. G. Shaw at two locations in Nigeria. In the southwestern location, neither the native grasses nor the sorghum varieties were infected, but most maize varieties were susceptible to downy mildew. In the north‐central location, differential sorghum lines T x 412, T x 430, FFBL, L1499, T x 415 and most maize varieties were systemically infected. Among the native grasses, onlyDactylactenium aegyptium(L.) P. Beauv. andRoettboelia cochinchinensis(Louv.) Clayton were partially susceptible to downy mildew. Oospores from diseased sorghum and conidia from both infected sorghum and maize genotypes were found to be involved in the downy mildew disease cycle in the north‐central location, while only conidia from infected maize were detected and caused disease on maize in the southwestern location. This suggests the presence of a sorghum pathotype of downy mildew which infects both maize and sorghum in the north‐central zone and a maize pathotype which infects only maize in the southwestern zone. Oospores could not be detected in infected maize plants or in soils in the southwestern zone; however, infected maize plants with abundant sporulation were found in some hydromorphic areas during the dry season.

ISSN:0967-0874    

DOI:10.1080/09670879309371752

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The False Pink Bollworm,Sathrobota (Pyroderces) simplex(Walsingham), was observed infesting open cotton bolls during the 1987/88 cotton growing season in the Punjab region of Pakistan. The larvae were, at that time, incorrectly identified as Pink Bollworm(PBW), Pectinophora gossypiella(Saunders). Their presence caused concern, as the area of infestation occurred in a field of cotton which had been treated with pheromone (gossyplure)to controlinfestation byP. gossypiella.Subsequently identification of the adults in the UK revealed that the majority of the infested bolls contained S.simplexand this was confirmed in trials conducted in thesame area during the1988/89cottongrowing season. This is the first record ofS. simplexin Pakistan. The importance of S.simplexas a pest of cotton, and the evaluation of a pheromone formulation for monitoring adult populations, is described. Its significance as a pest of cotton is discussed.

ISSN:0967-0874    

DOI:10.1080/09670879309371753

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Crop damage toSorghumcaused by the endangered blackbuck antelope(Antelope cervicapra)was estimated by (1) comparisons between grazed and ungrazed biomass, and (2) the dietary needs of a known population of blackbuck. Blackbuck were observed to penetrateSorghumfields a mean maximum distance of 4.6 m from the edge. Ungrazed dry biomass ofSorghumwas greater than dry grazed biomass(P< 0.001). Damage caused to every 100 m of vulnerable edge of a field was estimated to be 228 kg for the Velavadar National Park region in Gujarat, India, during 1989. A population of 300 blackbuck in the vicinity of Latuda and Katuda villages, Surendranagar district,’ Gujarat, was estimated to be responsible for a maximum potential loss of 48 600 kg of theSorghumcrop for one season valued at about Rs.29 000 in 1989. Prophylacticmeasures toameliorate the problem are discussed and, alternatively, methods and criteria to decide on monetary compensation to farmers are suggested.

ISSN:0967-0874    

DOI:10.1080/09670879309371754

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Incidence and geographical distribution of downy mildew(Peronosclerospora sorghi)on maize(Zea mays)were determined in a systematic survey of 181 maize fields in the major maize‐growing regions and ecological zones of Nigeria. Downy mildew was observed in the forest and Guinea savanna ecologies, but no disease was detected in other ecologies. Highest levels of disease incidence (63%) were observed in the forest zone, and progressively less disease incidence was found at the southern and northern Guinea savanna zones. Spatial pattern analysis indicated an aggregation and randomness of infected plants in the northern Guinea savanna and the forest zone, respectively. Disease incidence was positively correlated with the presence of downy mildew infected sorghum plants and relative amount of sporulation on infected sorghum(Sorghum bicolor)but negatively correlated with plant age and cropping pattern. Relative sporulation on maize plants was negatively correlated with age of maize plants. Higher levels of disease incidence were observed when the previous crop was either maize or sorghum than when previous crops were cassava, okra, tomatoes, or rice.

ISSN:0967-0874    

DOI:10.1080/09670879309371755

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The importance of natural biotype differences affecting insect pest status and consequent pest management is indicated and discussed, including the occurrence of such differences in association with resistance to pesticides. Data on observed differences, especially those affecting the capacity to damage stored grain, are presented forRhyzopertha dominica, Prostephanus truncatus, Sitophilus oryzaeandTribolium castaneum.Simple tests to discriminate between biotypes, in this capacity and in some other characteristics, are briefly described. It is proposed that such tests should be included where pest management improvements are a research objective, and that their potential usefulness in field situations, where the information obtained may be especially relevant, should be more widely considered.

ISSN:0967-0874    

DOI:10.1080/09670879309371756

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fruit and leaf spot of citrus caused byPhaeoramularia angolensiswas first observed in Angola and Mozambique in 1952. The disease has now spread to 15 countries, south of Sahara, and recently to Yemen, in the Arabian Peninsula. All citrus species are affected with grapefruit, with orange being the most susceptible.P. angolensisinfects foliage, fruit and stems. Severe infection causes leaves to abscise, fruit to ripen prematurely and drop, and young shoots to die back. Total loss of yield of marketable fruit is not uncommon in severely diseased orchards. In most of the countries where the disease is prevalent control is effected by extensive use of fungicides. Because of strong traditional trade links and the wind‐borne nature of the fungal spores the fungus is a potential threat to citrus production in the Middle East, Indian subcontinent and the Far East (which is the centre of diversity of citrus). This paper discusses the disease in Kenya against the background of work reported elsewhere. It is also intended to make citrus researchers and quarantine officers in developing countries aware of this destructive disease.

ISSN:0967-0874    

DOI:10.1080/09670879309371757

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Studies were conducted on smallholder plots in northern Togo from 1988 to 1991 to determine the possibility of applying treatments according to action thresholds. Thresholds were defined for the following pests:H. armigera, D. watersi, Earias sp., S. derogataandA. gossypii.The threshold programme was compared to the routine insecticide application programme involving five applications fortnightly beginning 50 d.a.s. An u.l.v. formulation of a mixture of deltamethrine and dimethoate at 3 litres/ha was applied, in both programmes. The results obtained showed that seed cotton yields were significantly different in 1991 (164 kg/ha less in the threshold treatment programme). Calculation shows that a reduction in treatments from five to three is not economical for the producer under the cropping conditions of the experiment. However, it could be worthwhile for the cotton‐growing development company, if solutions are found to the numerous practical problems brought to light by the experiments conducted over the past 4 years.

ISSN:0967-0874    

DOI:10.1080/09670879309371758

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A field study was conducted at the Regional Research Centre, Mtwapa and at the Msabaha subcentre in Kilifi District of Coast Province, Kenya between 1986 and 1989. The objective of this study was to investigate the effects of four land preparation methods and different weeding regimes on maize(Zea mays)grain yield. Land preparation methods were slashing, hand hoeing, tractor ploughing, and herbicide (paraquat) application.’ Weeding treatments were: no weeding, hand weeding at 4th leaf, 10th leaf, 16th leaf, 4th and 10th leaf, 4th and 16th leaf, 10th and 16th leaf stages, and weed control using a pre‐emergence herbicide (pendimethalin and atrazine—metolachlor mixture). Use of pre‐emergence herbicide had the same effect on grain yield as two weedings (at 4th and 10th leaf stages). The yields obtained with chemical weeding were significantly higher than those obtained with one early weeding (at 4th leaf stage). Land preparation methods did not differ significantly in their effect on maize grain yield. Weeding more than once generally gave a yield advantage of about 60–135% over one weeding. There was no significant interaction between land preparation methods and weeding treatments. The possible implications of these findings on maize grain yields in this region are discussed.

ISSN:0967-0874    

DOI:10.1080/09670879309371759

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor