摘要:

The economic threshold level of the mustard aphid,Lipaphis erysimi(Kaltenbach) was determined on the radish seed crop, var Punjab Sufed. Spraying oxydemeton methyl at 300 g a.i./ ha, was monitored at arbitrary set aphid levels from 25 to 150 aphids/plant. The maximum cost benefit ratio (1: 13.1) was achieved at an aphid level of 50 per plant, requiring three sprays. Spraying in the middle of February was the most crucial, as delay of 7 days from this stage resulted in significant decreases in yield in the fixed spray schedule and at the 75‐aphid level.

ISSN:0143-6147    

DOI:10.1080/09670878909371346

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The potato tuberworm,Phthorimaea operculella(Zeller) population size increased as the crop season progressed and was at its annual highest during the summer planting. A significant positive correlation was established between pheromone catches of adult moths, foliar larval populations and the plant infestation by potato tuberworm in all the six cropping seasons. Pheromone trap data could be used to predict foliar population and damage.

ISSN:0143-6147    

DOI:10.1080/09670878909371347

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Traps baited with synthetic codling moth,Cydia pomonella(L.), sex pheromone, were positioned at two heights in apple trees, 1.6–2.0 m and 3.5 m, to determine if height significantly influenced trap catch. To eliminate intertrap competition between traps at different heights, the traps were placed alternately high for a week, then low for a week, over an eight week period. Our results showed that the position of the trap in relation of the tree canopy was critical. The trap must be inside the tree canopy. In the absence of intertrap competition between high and low traps, there were no significant differences between catches in traps positioned in the top of the tree or traps at head height. Traps for monitoring codling moth in pest management programs will provide the same information when located where it may be easily reached, as when in the top of the tree.

ISSN:0143-6147    

DOI:10.1080/09670878909371348

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In surveys of coffee plantations in Chiapas, Mexico from 1983 to 1985 to assess the distribution and damage caused by the coffee berry borer, prior to parasite introduction levels of infestation were greatest near the Guatemalan border and varied with altitude, the borer was most numerous between 500–1000 m above sea level, corresponding to a mean annual temperature of 23 to 25 °C. Many berries are left on the tree and ground after harvest and high levels of attack were found in both places.

ISSN:0143-6147    

DOI:10.1080/09670878909371349

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

From preliminary samples of the coffee berry borer (Hypothenemus hampeiFerr.) in Chiapas, Mexico, various methods of calculating the number of samples needed for assessing the success of a parasitoid introduction scheme were reviewed, including those based on binomial, distribution‐free and Taylor's power law methods. The final choice of a method depends on the area to be sampled and time of year. Because of limitations on time for sampling, the high variance of the preliminary samples and the necessity of evaluating parasitoid impact over a wide area, it seems unlikely to be able to detect a significant drop of less than 20% in the borer population.

ISSN:0143-6147    

DOI:10.1080/09670878909371350

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Cowpea (Vigna unguiculata(L.) Walp) var. Ife Brown was infested with first instar larvae ofMaruca testulalisat three crop growth stages: flower primodia, flower bud and open flower stages. Successful establishment of larvae was possible only at the flower bud stage. An infestation of two larvae per plant was optimal for detecting differences in flower and pod production and difference in yield between infested and uninfested plant.

ISSN:0143-6147    

DOI:10.1080/09670878909371351

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Multilocation field trials on the chemical control of stemfly‐wilt complex due toOphimya phaseoliandFusarium oxysporumin early sown peas were conducted for 4 yr (1981–1984). Of the different combinations of insecticides/fungicides tested, the pre sowing treatment of pea seed (cv.Hara bona) with Aldrin‐30EC (0.5%) and Bavistin (0.05%) proved most effective in ensuring 95.2 and 98.3% reduction in plant mortality at the research farm and farmers fields respectively, besides increasing the yield by 16.00 q/ha over the control. The effect of this treatment on yield parameters (root nodulation, nodule weight, root weight and pod weight), reduction in severity of infection and residual problems are discussed.

ISSN:0143-6147    

DOI:10.1080/09670878909371352

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Studies of the geographic variability ofAscochyta rabieiwere done using chickpea cultivars of differing susceptibility under uniform growth room conditions. The pathogenicity of certain isolates particularly those from the Indian subcontinent and Western Asia was greater than that of most isolates collected in the Western Mediterranean. Several cultivars already deployed in breeding programmes showed stable resistance to the fungus, others with intermediate levels of resistance were less stable when exposed to a high disease pressure developed by the repeated passaging of isolates through them. In general differences in pathogenicity were attributed to variations in aggressiveness shown by the constant ranking of the cultivars used. Sporulation may not be linked to pathogenicity and significant statistical interactions with reversals in cultivar rankings suggests this to be an area for further study. Resistance toA. rabieiseems to be polygenic or at least oligogenic. In conditions of prolonged disease pressure some barriers to infection and/or spoulation may be overcome by pathogenic adaptation.

ISSN:0143-6147    

DOI:10.1080/09670878909371353

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In a study of the effect of initial infestation of chickpea, with one, two, three, four and five sexual pairs of pulse bruchid, up to F1(one generation) and F2(two generations), a highly positive correlation (r= 0.949) occurred between population in the F1and the number of pairs of beetles, but not up to F2generation. Significant correlations ofr= 0.921 andr= 0.385 between grain damage (%) and final population also occurred for the F1and F2generations, respectively, also high positive correlations (r= 0.974 for F, andr= 0.959 for F2) between loss in grain weight and population. The coefficients of determination revealed that 97% and 92% variability in loss in grain weight was due to the number of pairs of beetles initially released, their final population and per cent grain damage, for the F1and F2generations, respectively.

ISSN:0143-6147    

DOI:10.1080/09670878909371354

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The red bollworm,Diparopsis castaneaHamps is not yet a pest of cotton in Tanzania. However, in recent years cotton production has increased in the cotton quarantine zone and red bollworm larvae have been found on wild cottons in Mbeya region. These developments, which threaten the whole cotton industry, are discussed and steps to redress the situation suggested.

ISSN:0143-6147    

DOI:10.1080/09670878909371355

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor