ISSN:0143-6147    

DOI:10.1080/09670878009414914

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Laboratory studies were carried out to determine the course of poisoning and toxicity of some synthetic pyrethroid insecticides (bioresmethrin, cismethrin, cypermethrin, deltamethrin, fenpropathrin, fenvalerate and permethrin) against the desert locust. From doses in excess of the LD99all the insecticides were quick acting; from doses of about the LD99or less the insects are rapidly knocked down or show symptoms of poisoning, but may recover. The symptoms which follow treatment by the various insecticides are described. Although these insecticides are all highly toxic to locusts there are many other insecticides which are similarly toxic, can be sprayed at high concentrations and are much cheaper.

ISSN:0143-6147    

DOI:10.1080/09670878009414915

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A survey of yield losses in yams caused by soil pests showed that, of a wide variety of organisms causing damage, only termites (Amitermes), yam beetles, nematodes and various ‘rots’ caused significant losses. Damage was a poor indicator of yield loss which was estimated by assessing monetary values of damaged and undamaged tubers. A total of 114 farmers were surveyed during 1976–1977 in eight villages, two each in the Mokwa, Lokoja (Guinea savanna), Onitsha and Aba (forest) areas. The percentage of farmers sustaining total losses exceeding 8% in these areas was 10%, 8%, 2% and 35% respectively. The maximum losses sustained by individual farmers were 29% forAmitermes, 42% for yam beetle, 29% for nematode (Scutellonema) and 6% for ‘rots’ and all of these were from Obegu village near Aba. A trial using 2.5% aldrin dust to treat setts indicated that the increase in yields resulting from decreased damage byAmitermesand yam beetle would be profitable for 92–100% of farmers in Obegu, 24% in Ibere (both near Aba), 20% in each of the two Mokwa villages and none in the other villages.

ISSN:0143-6147    

DOI:10.1080/09670878009414916

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The status ofRhinacloa forticornisReuter, the brown mirid of Sea Island cotton in Barbados is discussed. Unsprayed cotton had higher sweepnet catches of mirids and had retained fewer fruiting forms than sprayed cotton. Photographs show the damage circumstantially attributed toR. forticornisin the match-head, flared square, flower bud, flower and boll stages; there is no leaf tattering. A field of unsprayed cotton matured very few bolls in the presence of large numbers of mirid although some of the Sea Island plants and wild cotton appeared to be resistant to mirid attack/damage. Early instars were definitely phytophagous, but the predatory habits of later stages reported elsewhere could not be confirmed. Early shedding delays crop formation and this should be prevented by spraying although control is usually obtained as a result of spraying against other pests.

ISSN:0143-6147    

DOI:10.1080/09670878009414917

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Physico-chemical studies of insecticide sprays applied by helicopter have been undertaken during the course of the WHO Phase II aerial spraying trials for riverineGlossinacontrol in Upper Volta during the 1977/78 dry season. A Bell 47G-4A helicopter was fitted with electrically operated rotary atomisers and the equipment was calibrated to apply insecticides at very low dosages (endosulfan 100 g/ha and deltamethrin 12.5 g/ha). This was achieved by the accurate metering of insecticide quantities to the atomisers and employing a technique of application which produced very small droplets from atomisers located along a boom on the port side of the helicopter. This method of installation allows the downwash of the main rotor of the helicopter to direct the spray droplets more effectively into the riverine canopy and is called the ‘unilateral’ technique. Distribution of insecticide deposits close to the ground during the morning were markedly different from the evening in open savanna, but not so in the riverine forest. There was evidence that droplets of approx 80 μm vmd penetrated more effectively than droplets of 150 μm vmd but a comparative evaluation of endosulfan applied at equivalent dosage rates (100 g/ha) and at these droplet sizes indicated both to be equally effective in reducingG. tachinoidesduring the first two weeks following the applications. Deltamethrin applied as a fine spray at a dosage rate of 12.5 g/ha gave similar reductions ofG. tachinoides. Studies of spray deposits within the habitat of the fly close to the ground and near the river's edge suggested that there was insufficient insecticide on the target surfaces to give a persistent deposit. However, there is evidence that deposits increased with increasing height, therefore the incidence of movement of tsetse flies during the night to resting sites within the upper parts of the riverine forest canopy may have an important bearing on their control. The ability of aerial sprays to penetrate the riverine forest canopy is of importance in the different vegetation zones and is of particular relevance in the more densely forested areas of the Southern Guinea Savanna zone where studies have yet to take place.

ISSN:0143-6147    

DOI:10.1080/09670878009414918

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The construction of a live trap for small rodents, which has been named the Serengeti Trap, is described. Some aspects of its working efficiency, applicability, durability and availability are presented. A comparison of choice, by the grass ratArvicanthis niloticusDesmarest is made between the Serengeti and Longworth traps.

ISSN:0143-6147    

DOI:10.1080/09670878009414919

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Cassava bacterial blight, first observed in Nigeria ih 1971, caused an estimated loss of 25 million naira in cassava production in East Central State of Nigeria in 1976. Results in the present study showed that yield was reduced from 10.61 million t/ha at severity class 1.77 to 6.22 million t/ha at severity 2.01. Increasing K content of the leaves by K-fertilization from 0 kg K2O/ha to 180 kg K2O/ha in a soil with 0.25% N, 20.08 ppm P, 2.85 m.e. Ca/100 g, 1.17 m.e. Mg/100 g and 0.20 m.e. K/100 g tended to reduce the severity and enhance the yield. The main effects of N- and P-fertilization at rates up to 60 and 30 kg/ha respectively were not significant with respect to root yield. Highest root yields were obtained with the fertilizer level of 30 kg N/ha, 15 kg P2Os/ha and 180 kg K2O/ha.

ISSN:0143-6147    

DOI:10.1080/09670878009414920

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Crop loss due toChoanephora cucurbitarumwas estimated at between 7% and 20% in southern Nigeria. Injury is an important factor inChoanephorapod rot infection. Chloroneb, thiram, thiram + BHC, fentin acetate, captafol, fentin hydroxide and captan, in laboratory bioassay, inhibited the mycelial growth while thiram, thiram + BHC and captan inhibited conidial germination ofC. cucurbitarum. The same fungicides which inhibited conidial germination reduced initial infection rate in the field but seemed to aggravate infection rate subsequently.

ISSN:0143-6147    

DOI:10.1080/09670878009414921

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Nine fungicides testedin vitroinhibited the growth of all pathogens associated with basal stem rots at 200 ppm active ingredient except chloroneb and mancozeb which were ineffective onPythium aphanidermatum. Thiram + BHC, captafol, captan, thiram and fentin hydroxide gave effective control of pre-emergence damping-off caused byP. aphanidermatumandCorticium rolfsiiin cowpea seeds, but failed to control post-emergence damping-off in the glasshouse. Soil drench with an aqueous suspension of thiram, thiram + BHC and captan controlled both pre- and post-emergence damping-off. In field trials, however, there was no significant difference between seed dressing alone and a combination of seed dressing and soil drench both in terms of percentage plant survival and grain yield.

ISSN:0143-6147    

DOI:10.1080/09670878009414922

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Ufra, caused by the stem nematode,Ditylenchus angustus(Butler, 1913) Filipjev, 1936, is a serious disease of deepwater rice in southern Bangladesh. It was studied between 1977 and 1979 as part of a joint project with the Overseas Development Administration at the Bangladesh Rice Research Institute. Three symptom types are distinguished according to the extent of panicle emergence: Ufra1 (none), Ufra2 (partial) and Ufra3 (complete). All three represent total loss from that panicle. The number of Ufra2 as a percentage of the total number of panicles present in a specified area is selected as a disease index (UfraII). A function relating yield to the level of UfraII is proposed on the basis of selective samples from a field with a well-defined ufra patch. This function is compared with another derived from random samples in different fields along a linear transect through an area where ufra is endemic. Loss of panicle density, i.e. panicles/m2, is identified as a major component of yield loss, approximately equal to the loss associated with all three symptom types added together. Although severe and widely distributed throughout the southern part of the deepwater rice region in 1977 and 1978, it was very difficult to find in 1979 when there was a spring drought. Ufra is worse in wet years, in areas which flood early, and where the crop is harvested late. The length of the over-winter decay phase appears to be a critical factor regulating the survival of the pathogen from one season to the next. This suggests an approach for ufra control.

ISSN:0143-6147    

DOI:10.1080/09670878009414923

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor