Structure-activity relationship development of dihaloaryl triazole compounds as insecticides and acaricides. 1. Phenyl thiophen-2-yl triazoles

An extended lipophilic system that incorporated some key elements of first-generation 2,6-dihaloaryl actives, such as 1, demonstrated desirable efficacy against chewing insects as well as sap-feeding insects. These four-ring systems, based on 2, were accessed primarily via Suzuki couplings of halothiophene derivatives with appropriately substituted boronic acids. In particular, phenylthiophene systems that incorporated haloxyether groups, such as those in 3, 4, and 5, had the broadest spectrum of activity across chewing and sap-feeding insect pests. Expansion of this structure-activity relationship to include compounds with differing substitution patterns on the thiophene-C-ring and aryl-D-rings was undertaken. The synthesis and insecticidal activity of 3-aryl-5-(thiophen-2-yl)-1-methyl-1H-[1,2,4]triazoles will be described.     

Improving participatory varietal selection processes: participatory varietal selection and the role of informal seed diffusion mechanisms for upland rice in Ghana

This paper considers the process of Participatory Varietal Selection (PVS) and presents approaches and ideas based on PVS activities conducted on upland rice throughout Ghana between 1997 and 2003. In particular the role of informal seed systems in PVS is investigated and implications for PVS design are identified. PVS programmes were conducted in two main agroecological zones, Forest and Savannah, with 1,578 and 1,143 mm of annual rainfall, respectively, and between 40 and 100 varieties tested at each site. In the Savannah zone IR12979-24-1 was officially released and in the Forest zone IDSA 85 was widely accepted by farmers. Two surveys were conducted in an area of the Forest zone to study mechanisms of spread. Here small amounts (1–2 kg) of seed of selected varieties had been given to 94 farmers. In 2002, 37% of 2,289 farmers in communities surveyed had already grown a PVS variety and had obtained seed via informal mechanisms from other farmers, i.e. through gift, exchange or purchase. A modified approach for PVS is presented which enables important issues identified in the paper to be accommodated. These issues include: utilising existing seed spread mechanisms; facilitating formal release of acceptable varieties; assessing post-harvest traits, and; the need for PVS to be an ongoing and sustainable process.     

Variation in the expression of specificity in two maize diseases

Summary Ten inbred lines from the open-pollinated maize variety Jarvis were selected from 51 randomly collected lines to represent a wide range of susceptibility to one isolate each of Bipolaris maydis or Colletotrichum graminicola. Ten isolates of each pathogen were selected for a range of virulence on a maize line with average resistance. Resistance and virulence ratings were based on lengths of lesions that developed on leaves of greenhouse-grown seedlings inoculated with 5 l droplets of suspensions of known spore concentrations. For each disease the ten maize lines were inoculated in all possible combinations with the ten pathogen isolates. The experiment was run six times with each pathogen. Analysis of variance for individual trials indicated a significant interaction between maize lines and B. maydis isolates in all six trials and between maize lines and C. graminicola isolates in four of six trials. For both diseases. the combined analysis over all six trials revealed no significant interaction. Apparently the expression of specificity in these host-pathogen interactions is variable.     

Atmospheric monitoring network operations and results in Canada

Atmospheric monitoring activities in Canada relevant to the long-range transport of atmospheric pollutants and the ‘acid rain’ problem are reviewed. Particular aspects examined are network objectives, station density and location, sampling protocol, and quality assurance. Results from a number of these networks are presented for the purpose of outlining the nature and extent of air and precipitation contamination by pollution released in eastern North America. Examples discussed include: the spatial distribution of acidic wet deposition, the temporal variation of acid-related substances in both air and precipitation, an episode of long-range transport, and the impact of acidic emissions on the Arctic atmosphere. Acidic wet deposition is greatest in Canada east of the Manitoba-Ontario border. In 1978, it ranged from 18 to 46 mmol H⁺ m^?2 yr^?1 in the southern half of eastern Canada, with maxima in southern Ontario (44 mmol H⁺ m^?2 yr^?1) and southwestern Quebec (46 mmol H⁺ m^?2 yr^?1). Western Canada receives less acidity in precipitation, but areas of some concern are the Pacific Coast (10 mmol H⁺ m^?2 yr^?1) and to a lesser extent northern Alberta and Saskatchewan (3 to 5 mmol H⁺ m^?2 yr^?1). Acidic emissions from mid-latitude sources which reach the Arctic in winter cause an increase in the acidity of snow from a pH of approximately 5.6 in the summer to values of 4.9 to 5.1 in January through March.     

Effect of collembolan grazing upon nitrogen and cation leaching from decomposing leaf litter

Fragmented oak litter was incubated in the laboratory for 4 months with and without collembola. The effects of the animals upon fungal standing crop and leaching of inorganic nitrogen and cations was monitored over this period.The results showed that the fungal standing crop was higher in the presence of small numbers of animals than in litter lacking animals, yet at higher grazing intensities the fungal standing crop fell markedly. Significant increases in the leaching of ammonium, nitrate and calcium occurred as a consequence of animal grazing, but potassium and sodium losses from the litter were unaffected.     

Grain Size Partitioning of Mercury in Sediments of the Middle Odra River (Germany/Poland)

The Odra River is the second largest river in Poland, running from Czech Republic through a large part of Poland before entering the Baltic Sea. For the last century its catchment area has been heavily polluted by anthropogenic emissions. The aim of this study is to determine the distribution of mercury in different grain size fractions of surface sediments from the middle course of the Odra River. Mercury concentrations were determined in bulk sediments of different grain size fractions using the cold vapor atomic fluorescence spectrometry method. The total mercury concentration in bulk sediments varied from 0.051 to 1.31 mg/kg dry weight. The concentration of total mercury was determined in the grain size fractions <0.2, 0.2–0.5, 0.5–1.0, 1.0–2.0 and >2.0 mm to be (in mg/kg d.w.): 0.118–2.99, 0.033–0.99, 0.034–1.17, 0.035–1.97 and 0.017–3.65, respectively. Gradual decrease in the mercury concentration with increasing grain size from fine to coarse fraction has been observed only for sediments taken from the river bed. Although, no similar gradual decrease in the mercury concentrations has been observed for sediments from the river banks, finer sediments (<0.2 mm) still tend to show higher concentrations of mercury.     

Wear rate of animal-drawn ploughshares in selected Ghanaian soils

Rapid ploughshare wear was identified as a major constraint facing animal traction farmers in Ghana. The objectives of this study were to: (i) identify the types of animal-drawn ploughshare used by farmers and their production methods, (ii) develop and test a new cast steel share and compare its performance with existing ploughshares, and (iii) determine the factors responsible for the rapid wear and durability of ploughshares in selected soils in the country. To address this problem, new and used ploughshares were collected from farmers, blacksmiths and foundries and their microstructure, chemical composition and hardness were studied. Based on the above studies, new cast steel ploughshares were developed. On-farm tests were conducted on the new shares for wear and durability in the major animal traction soils in the country. On-station field trials with tractor-drawn shares were carried out to compare the performance of the new ploughshares with the imported and local blacksmith versions. Multivariate statistical methods were used to analyse the similarities among the shares with respect to producers, chemical composition, share hardness, soil physical factors (moisture content, bulk density, cone index and soil texture) and their relationship to wear rate. When pulled by tractor, the average wear rates of the imported, improved and blacksmith shares in soils containing 50%, 64% and 74% sand were 297, 362 and 562 g/ha, respectively. The average wear rates of the new share when pulled by animals in the major soil classifications were: Eutric Plinthosols, 146 g/ha; Plinthic Lixisols, 164 g/ha and Haplic Lixisols, 176 g/ha, respectively. This gave an average durability of 3–8 ha/share before the farmer declares the new ploughshare completely worn. This compares with 1–2 ha and 2–5 ha per share wear rates for the blacksmith-forged and the imported shares, respectively. The study concluded the new cast steel ploughshares have qualities of enhanced durability and toughness similar to the imported versions and more durable than the local blacksmith shares and have prospects for mass production.     

A method for measuring anthocyanins after removing carotenes in purple colored carrots

A method used for anthocyanin measurement in cranberry resulted in a problem of interference by carotene in purple carrot extracts. We developed a method suitable for a purple color carrot breeding program. The new method includes a three step process: (1) extraction of anthocyanins using a small amount of acidified ethanol (95% ethanol in 1.5 N HCl); (2) removal of carotenoids present in the extract; and (3) measurement of total anthocyanins with a spectrophotometer. The purple colored carrots analyzed contained around 38–98 mg anthocyanin per 100 g fresh weight. The new method can be efficiently used in a breeding program for the development of purple colored carrots for nutritional benefits and a source of a natural pigment.