摘要:

The critical period of weed‐crop competition was studied in greengram(Vigna radiate)during the monsoon seasons of 1982 and 1983, the summer seasons of 1983 and 1984 and in blackgram(Vigna mungo)during the monsoon seasons of 1982 and 1983. The major weed species during the monsoon seasons wereEchinochloa colonum, Dactyloctenium aegyptium, Eleusine indica, Digitaria sanguinalis, Celosia argentea, Phyllanthus niruri, Cleome viscosa. Cyperus rotundus and C. iria.During the summer seasonsE. colonum, D. aegyptium, Physalis minima, Portulaca quadrifidaandC. rotunduswere the major weed species. Competition during the first 15 days after sowing (d.a.s.) in greengram during the summer season had only a small depressing effectongrain yields. Grain yields of both crops during two seasons increased significantly with the increase in weed‐free duration up to 30 d.a.s. However, a weed‐free condition maintained beyond 30 d.a.s. induced no further improvements in grain yields. Weed emergence and growth 30 d.a.s. were low and suppressed by the crops. The period during the first 30 d.a.s. for monsoon‐planted crops of greengram and blackgram, and 15–30 d.a.s. for a summer‐planted crop of greengram was found to be critical for crop‐weed competition.

ISSN:0143-6147    

DOI:10.1080/09670879109371562

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In an effort to identify chemicals for post‐emergence control of broomrape,Orobanche cernuaLoefl, on tobacco, 3 mineral oils (diesel oil, kerosene and thinner oil used in paints) and 12 plant oils(viz.castor oil, coconut oil, cottonseed oil, dalda, gingelly oil, groundnut oil, linseed oil, mustard oil, neem oil, palm oil, sunflower oil and safflower oil) were tested.The oils were applied on young shoots (unflowered) at one, two, three, four and five drops/shoot with a dropper. All three mineral oils showed quick knock‐down effect within 24 hours: plant oils, except dalda, were also effective but slow in action. The optimum dosages were one or two drops/shoot. Mineral oils were phytotoxic to tobacco leaf and plant oils were not. An applicator was developed to apply oils by swab method in field.

ISSN:0143-6147    

DOI:10.1080/09670879109371563

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In glasshouse pot experiments 25 cowpea lines were exposed to samples of the parasitic weedsAlectra vogeliiBenth., from several localities in West and Southern Africa, andStriga gesnerioides(Willd.) Vatke from Mali. The lines used were mainly those reported to have resistance to one or other parasite. No general cross‐resistance was observed and the resistance genes are assumed to be different for the two parasite species. Cowpea lines from Botswana, exposed to BotswanaAlectrasamples, showed responses ranging from complete resistance to susceptibility, in keeping with their reported behaviour in the field. All Botswana lines, however, showed almost complete resistance toAlectrasamples from West Africa. It is concluded that there is an important difference between West and Southern African populations ofA. vogelii.On the basis of these results it should be relatively easy to develop Alectra‐resistant cowpea varieties for use in West Africa.

ISSN:0143-6147    

DOI:10.1080/09670879109371564

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Field trials were conducted at Kadawa in the 1983/4 and 1984/5 dry seasons to evaluate some herbicide treatments for weed control in transplanted irrigated sweet pepper (Capsicum annuumL., var. California mild). In the 1983/4 dry season, mixtures of metolachlor with metribuzin at 1.5 + 0.25 and pendimethalin plus linuron at 1.5 + 0.75 kg a.i./ha, each followed by supplementary hoe‐weeded control. Without supplementary hoe‐weeding, mixtures of linuron with oxadiazon and alachlor each at 0.75 + 1.5 kg a.i./ha and metolachlor plus metobromuron at 1.25 + 1.25 kg a.i./ha resulted in yields comparable to the hoe‐weeded control. In the 1984/5 dry season, linuron at 0.75 kg a.i./ha in mixture with either diphenamid, metolachlor, oxadiazon or chlorthal dimethyl ester at 3.0,1.5,1.5 and 10.0 kg a.i./ha, respectively, as well as metolachlor plus metobromuron at 1.5 + 1.5 kg a.i./ha, all supplemented with one hoe‐weeding, combined effective weed control with high pepper fruit yield comparable to the hoe‐weeded control. In this study unchecked weed growth throughout the crop life cycle resulted in 90% and 97% losses in sweet pepper fruit yield compared with the approximate maximum obtained in the 1983/4 and 1984/5 dry seasons, respectively.

ISSN:0143-6147    

DOI:10.1080/09670879109371565

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Field trials were conducted for two seasons with the objective of testing the comparative efficacy of herbicides applied singly or in combination, and the integration of chemical and manual methods of controlling weeds in grain sorghum. All the treatments reduced the density and dry weights of dominant weeds, and increased the grain yields compared to weedy control plots. Treatments having metolachlor at 1.0–1.25 kg ha−1, a combination of atrazine + metolachlor, sequential application of metolachlor and bentazon, atrazine at 0.75 and metolachlor at 1.0 kg ha−1as pre‐emergence followed by one manual weeding around 30 days after sowing were superior to the rest. The grain yield from the above herbicide‐treated plots did not differ significantly from the yields of plots which were repeatedly hand‐weeded. However, atrazine alone at all rates or in combination with other herbicides significantly reduced the sorghum height and stover yields.

ISSN:0143-6147    

DOI:10.1080/09670879109371566

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Poor economic return from perennial aromatic grasses during a planting year results from the high cost of cultivation, on account of planting, and lower yields, largely due to slow crop growth rate and high vulnerability of aromatic grasses to weeds, which are poorly managed In the absence of suitable weed control measures. Field experiments were established in July 1982 to examine the suitability of organic mulch (distillation waste of citronella Java) and herbicides in three important perennial aromatic grasses, citronella Java(Cymbopogon winterianusJowitt), lemongrass(C. flexuosus(D.C.) Stapf) and palmarosa (C.martiniiStapf var.motia) fortwo harvest years (1981–82 and 1982–83) under a subtropical climate at Lucknow. Weeds caused an average 40% reduction in herb and oil yields in the first harvest year as against 6% In the second. Organic mulch 3 t/ha, oxyfluorfen 0–5 kg/ha, diuron 1.5 kg/ha and simazine 1.5 kg/ha gave herb and oil yields equal to weed‐free check, and proved superior to the conventional method, which yielded 20% less than weed‐free check in the first harvest year. Organic mulch was found to be most competitive over other promising treatments. Palmarosa followed by lemongrass had a better weed‐suppressing effect than citronella Java.

ISSN:0143-6147    

DOI:10.1080/09670879109371567

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A survey to determine the species of ticks infesting camels, sheep and goats in the semi‐arid rangelands of Kenya showed thatHyalomma trancatum, Hyalomma dromedariiandRhi‐picephalus pravuswere the most abundant, in that order. Most of the ticks were restricted to the predilection sites with evidence of tissue damage. When this occurred on the lower extremities of the limbs, abscesses and lameness developed. In camels, ticks attached on the eyelids causing excessive irritation, lacrimation and conjunctivitis. Thin and thick blood smears were negative for hae‐moparasites, and during the study period no animals died as a result of ticks and tick‐borne diseases. The absence of tick‐borne diseases and the low numbers of ticks in the hosts demonstrated that the indiscriminate use of acaricides, especially on camel herds, is unnecessary. Conventional methods of herd spray are suggested, but the use of slow‐release devices and pour‐ons would be more suitable in this environment if it can be demonstrated that they are economically justifiable.

ISSN:0143-6147    

DOI:10.1080/09670879109371568

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This study was done to determine the extent of tree damage (primarily bark‐stripping) caused by blue monkeys(Cerco‐pithecus mitis)in the Sokoine University of Agriculture Training Forest in the Mount Meru Forest Plantations. The impact of monkeys was extensive; 88.7% of the pine (Pinus patula)amd 79.5% of the cypress(Cupressus lusitanica)trees were damaged. Intermediate pine trees were damaged more than dominant trees, whereas dominant cypress trees incurred the most damage. Suppressed trees of both species were least damaged. For all types of trees the most severe damage occurred at the middle and top.of the tree trunks. Damage was low in the rain season and increased in the dry season, peaking in June and July when 22% of the trees were damaged. Differences in the ease of bark peeling and nutritional elements in the bark of the two species, and shortages of natural foods, are discussed as possible explanations for the variations in damage between seasons, tree species and types of trees.

ISSN:0143-6147    

DOI:10.1080/09670879109371569

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Rodent damage to crops in developing countries is widely known. In Madagascar the most important rodent pest is the roof rat(Rattus rattus).The impact of the rat on rice crops was studied in the region of Lake Alaotra, the principal rice‐producing region of Madagascar. Evaluation of rodent damage was conducted in 591 parcels just before harvesting. The average damage value was low (on average less than 1%) and the average losses per hectare were also low at less than 100 kg paddy rice/ha. Differences were significant, depending on the locality and the presence of good refuge habitat for rats around the ricefield. The rice variety and agronomic practices did not influence the damage levels. The low damage level does not require the use of rodenticide in a rat control programme.

ISSN:0143-6147    

DOI:10.1080/09670879109371570

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In an experiment, house crows(Corvus splendens)were estimated to damage 65.1% of sprouting sunflower(Helianthus annuus)seedlings at Ludhiana, Punjab (India). Seed treatments with 0.5% thiram (tetramethylthiuram sulphide) and 0.5% copper oxychloride [3Cu(OH)2CuCI2], both commonly used fungicides, did not reduce bird damage. The number of seedlings in a plot from which birds were excluded by netting was significantly greater than, that in any of the chemical treatments as well as in the untreated control.

ISSN:0143-6147    

DOI:10.1080/09670879109371571

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor