bluuebunny/crossref_metadata_2025_split huggingface dataset:
In‐vivo evaluation of adjuvants for more effective control of celery leaf‐spot (Septoria apiicola) and powdery mildew (Erysiphe graminis) of wheat with fungicides
Authors: Amer Mostafa A. , Hoorne Dirk , Poppe Josef 
Published: November 2006

AbstractThe effects of seven adjuvants (at 0, 0.5, 1.0 and 2.0 g litre−1) on the efficacies of four fungicides al 0.5 g litre−1 were studied in the laboratory for the control of leaf‐spot in celery (caused by Septoria apiicola) and powdery mildew on winter wheat (caused by Erysiphe graminis). The most effective fungicides for controlling leaf‐spot were: tebuconazole + triadimenol = flutriafol > mancozeb + oxadixyl > prochloraz. However, addition of adjuvant to the fungicides gave a modified pattern of effectiveness. The efficacy of flutriafol was strongly enhanced by addition of all adjuvants, but those of prochloraz and mancozeb+oxadixyl only partially so. The tested adjuvants were mineral oil + surfactant, a polymer/alkoxylated alkyl ether blend, an ethoxylated alkylphenol, an ethoxylated hexitan ester blend, an ethoxylated nonylphenol and an alkylpolysaccharide‐ based adjuvant mixture. However, the addition of adjuvants to tebuconazole + triadimenol had a negative effect. Of all the adjuvants tested, the nonylphenol ethoxylate and a mixture of mineral oil /surfactant and alkylpolysaccharides gave the highest efficacy with the fungicides, while the mineral oil/surfactant and the alkylpolysaccharides alone were less effective. There was a positive relationship between high concentrations of adjuvants and their effectiveness, but there were some exceptions.The most effective fungicides for control of powdery mildew in wheat were prochloraz, mancozeb + oxadixyl and tebuconazole + triadimenol. There was a linear relationship between the high efficacy of the fungicide and the concentration of adjuvants to control powdery mildew in wheat. The highest concentration of adjuvant (2‐0 g litre−1) gave the highest efficacy for the fungicides.
Characterizing pesticide and surfactant penetration with isolated plant cuticles
Authors: Bukovac Martin J. , Petracek Peter D. 
Published: November 2006

AbstractA survey is presented of the use of isolated leaf and fruit cuticles in studying foliar penetration. Isolated cuticles, which represent the prime barrier to penetration, provide a physical system with which transport studies can be conducted under well‐defined and highly controlled conditions while avoiding the physiological effects of biologically active compounds on the system. Most studies with isolated cuticles have focused on sorption, desorption and infinite‐dose cuticular transport of compounds in aqueous systems. Partition coefficients can be calculated for pesticides from sorption data, thereby yielding information on the solubility of the compounds in the cuticle. Permeance and diffusion coefficients can be calculated from cuticular transport studies. These transport parameters provide for a better understanding of the mechanisms of cuticular penetration. Further, they are useful in comparing both the penetration characteristics of selected compounds and permeability of cuticles. Transport systems, using isolated cuticles, may be used to quantify the effects of spray additives on pesticide penetration. A finite‐dose system is described that may be useful in studying spray droplet/deposit interactions with the cuticle and, concurrently, following transcuticular penetration from droplets/deposits on the surface. These systems may prove useful in optimizing spray formulations and spray parameters, leading to more efficient pesticide development and application.
Fungicidal activity of the polyamine analogue, keto‐putrescine
Authors: Foster Sally A. , Walters Dale R. 
Published: November 2006

AbstractThe polyamine analogue, keto‐putrescine, was shown to provide substantial control of infections by six economically important plant pathogens, with EC50 values ranging between 57 and 82 mg litre−1. However, keto‐putrescine was relatively less effective in vitro against Phytophthora infestans, Pyricularia oryzae and Pyrenophora avenae, with EC50 values ranging from 145 to 340 mg litre−1. In contrast, the polyamine analogue N‐acetylputrescine had to effect on in‐vitro growth of P. avenae or P. oryzae or infection of barley seedlings with powdery mildew. When P. avenae was grown in the presence of keto‐putrescine, there were small, insignificant reductions in ornithine decarboxylase activity, with more substantial, significant reductions in S‐adenosylmethionine decarboxylase activity. These changes were accompanied by a 43% reduction in spermidine concentration and increased concentrations of spermine and cadaverine.
The dietary toxicity of flocoumafen to hens: Elimination and accumulation following repeated oral administration
Authors: Eadsforth Charles V. , Gray Alan , Huckle Keith R. , Inglesfield Christopher 
Published: November 2006

AbstractIn a dietary toxicity study, laying hens received a diet containing the rodenticide flocoumafen at concentrations of 1.5, 5, 10 and 50 mg kg−1 for five consecutive days. The LC50 at termination following a 28‐day observation period was 16.4 mg kg−1.Livers of birds which received doses of flocoumafen between 5 and 50 mg kg−1 had concentrations of flocoumafen (1.5 nmol g−1) that were independent of dose. The data indicate the presence in hen liver of a saturable high‐affinity flocoumafen binding site with similar characteristics and capacity to that of the quail and rat. Residues of flocoumafen in samples of breast and leg muscle were low in all exposure groups. Higher, dose‐related residues were found in samples of abdominal fat and skin‐associated fat and there was a clear demonstration of the transfer of dose‐related residues into eggs.In a separate study in which hens were dosed with [14C]flocoumafen for five consecutive days at a daily rate of 1 and 4 mg kg−1 body weight, the majority (68 %) of the daily radioactive dose was eliminated over the following 24 hours via excreta. Residues in liver at death or when killed accounted for < 1 % of the cumulative administered radioactivity. Residues in eggs were located primarily in the yolk with maximum concentrations 1.0 mg kg−1 or 0.18% of the low dose; 2.1 mg kg−1 or 0.06% of the high dose as [14C]flocoumafen equivalents were observed at 10 days after start of dosing. Some 40 % of the total activity in the yolk was unchanged flocoumafen.
Foliar uptake of organosilicone surfactant oligomers into bean leaf in the presence and absence of glyphosate
Authors: Zabkiewicz Jerzy A. , Stevens Peter J. G. , Forster W. Alison , Steele Kevin D. 
Published: November 2006

AbstractThe nonionic organosilicone surfactant ‚Silwet’︁® L‐77TM (1, 2 and 5 g litre−1) and [14C]glyphosate‐monoisopropylammonium (10 g litre−1 a.e.), were applied, alone and in combination with each other, to the upper surfaces of leaves of Vicia faba L. plants growing in a controlled environment. Over 80% of the glyphosate was taken up within 10 min in the presence of 5 g litre−1 L‐77, with no further uptake over the remaining period. A similar pattern of uptake was observed with 2 g litre−1 L‐77, but only 30% was taken up initially. In the presence of 1 g litre−1 L‐77 initial glyphosate uptake was only 15%, but uptake continued, subsequently reaching c.25% after 360 min, this behaviour being essentially the same as that of glyphosate when applied without surfactant. The uptake of L‐77 was not significantly affected by the addition of glyphosate, being c.80% within 10 min at 5 g litre−1, but with a slow, further increase of c.12%. At 2 g litre−1 uptake was c.45% within 10 min, rising to c.70% by 360 min. The 1 g litre−1 solutions showed a similar pattern, with uptake increasing from c.35% at 10 min to over 60% after 360 min. In the absence of glyphosate, individual L‐77 oligomers penetrated at similar rates. In the presence of glyphosate, however, some discrimination was evident among the oligomers, in particular when the surfactant was added at 1 g litre−1. Literature on the foliar uptake of surfactants is reviewed and discussed in relation to the results of this study.
Diffusion of three ethoxylated octylphenols across isolated plant cuticles
Authors: Coret Joël , Gambonnet Bernadette , Brabet Frederic , Chamel André R. 
Published: November 2006

AbstractThe diffusion of three polydisperse [3H]ethoxylated octylphenols (5, 10 and 16 EO) through isolated plant cuticles was studied using diffusion half‐cells and droplet application. The diffusion half‐cells were used to determine the influence of ethylene oxide (EO) content and of surfactant concentration on the diffusion of the surfactants across the cuticle at a relatively constant concentration gradient. The influence of EO content, of temperature and of surrounding relative humidity on diffusion of the surfactants across the cuticle was determined with droplet application.Measurements in diffusion half‐cells showed that flux was lowest for OP16 in comparison to OP5 and OP10. Diffusion coefficients were 0.92, 3.17 and 2.18 × 12−12 cm2 s−1 for OP5, OP10 and OP16 respectively in pepper fruit cuticles. Flux of OP10 across pepper fruit cuticles increased with surfactant concentration in the donor cell (from 5 to 40 g litre−1), the diffusion coefficient of OP10 in the cuticle rising from 3.79 to 21.3 × 10−12 cm2 s−1.Surfactant penetration through pepper fruit and rubber‐plant leaf cuticles was initially very rapid after droplet application, decreasing gradually after 24 h. Flux of OP16 across cuticles of both species was lower than for the other two octylphenols. Penetration of OP10 and OP16 through pepper fruit cuticles was greater at low (40%) than at high (95%) relative humidity. Transfer of OP10 increased considerably as temperature increased from 5°C to 30°C. The value obtained for the diffusion activation energy was −70.3 kJ mol−1.The experimental results are discussed in the light of the free‐volume theory with respect to diffusion of organic molecules in polymers.
The role of surface tension of spreading droplets in absorption of a herbicide formulation via leaf stomata
Authors: Buick Rosalind D. , Buchan Graeme D. , Field Roger J. 
Published: November 2006

AbstractThe foliar absorption by field bean (Vicia fabu L.) of triclopyr‐triethylamine from solutions containing an organosilicone surfactant, ‚Silwet L‐77’︁ at 0, 1.0, 2.5 and 5.0 ml litre−1, was investigated using fluorescence and radiotracer studies. Physical characteristics such as formulation surface tension and contact angles of droplet formed on the field bean leaf were determined and combined to obtain a critical surface tension value (γcritical) of 19.5–22.9 mN m−1 for the adaxial leaf surface. The apparent surface tensions of the three formulations containing L‐77 were equivalent and low, an average of 22 mN m−1, which would be sufficiently low to permit stomatal infiltration. The presence of L‐77 at 2.5 or 5.0 ml litre−1 significantly enhanced the uptake of triclopyr‐triethylamine into the leaf, particularly via stomatal pore regions. However, stomatal uptake from solutions containing 0 or 1.0 ml litre−1 L‐77 was limited or non‐existent. A phenomenon termed ‚adsorptive dilution’︁ is proposed to explain the absence of stomatal infiltration with the 1.0 ml litre−1 formulation. This involves a migration of surfactant from the bulk solution to the expanding droplet surfaces as the droplet spreads. This dilutes the surfactant concentration within the bulk solution, which can in turn increase surface tension.
Using chlorophyll fluorescence induction for a quantitative detoxification assay with metribuzin and chlorotoluron in excised wheat (Triticum aestivum and Triticum durum) leaves
Authors: Ducruet Jean‐Marc , Sixto Hortensia , Garcia‐Baudin José‐María 
Published: November 2006

AbstractChlorophyll fluorescence induction was used as a probe to detect herbicide detoxification in tolerant or susceptible wheat cultivars. Experimental conditions have been carefully examined for establishing detoxification kinetics of chlorotoluron and metribuzin, two photosystem‐II‐inhibiting herbicides. After a root treatment, leaves were cut, placed in glass tubes and maintained in the dark. The fluorescence induction rise was examined repeatedly and detoxification kinetics were established from these data for the same position on the individual leaves. The herbicide‐dependent fluorescence rise decreased within hours in chlorotoluron‐tolerant but not in susceptible Triticum aestivum cultivars. In contrast, no significant reversion could be detected after metribuzin application in both tolerant and susceptible cultivars of Triticum durum. Near the fluorescence‐determined half‐inhibition of photosystem II, linear detoxification kinetics were obtained in individual leaves, thus providing an accurate measurement of relative detoxification rates.
The toxicity of brodifacoum wheat bait to the field rodents Microtus guentheri and Meriones tristrami
Authors: Moran Shmuel 
Published: November 2006

AbstractThe toxicity of the anticoagulant brodifacoum to the field rodent species Microtus guentheri (Danford & Alston) and Meriones tristrami Thomas was tested in the laboratory. Brodifacoum 0.05 g kg−1 whole‐wheat bait was offered to the animals without additional food. The LD50 calculated for M. guentheri was 2.28 mg kg−1 body weight. Brodifacoum was found to be more toxic to M. tristrami; the LD50 was c. 0.8–0.9 mg kg−1 body weight. The toxicity data served to plan the doses of bait to be broadcast in the field.
Mobilities of organic compounds in reconstituted cuticular wax of barley leaves: Determination of diffusion coefficients
Authors: Schreiber Lukas , Schönherr Jörg 
Published: November 2006

AbstractIsolated cuticular wax, obtained from barley leaves, was mixed with 14Clabelled organic chemicals including aromatic pesticides and long‐chain linear alkanes, alcohols and acids. These mixtures were reconstituted from the melt and labelled chemicals were desorbed from the wax by immersing the wax samples in aqueous phospholipid suspensions. Diffusion coefficients (D) of radiolabelled test compounds in the wax were derived from desorption kinetics. Diffusion coefficients ranged from 10−17 to 10−22 m2 s−1 and decreased rapidly with increasing molar volumes of solutes. However, size selectivity of D was much more pronounced with the linear, long‐chain molecules than with the aromatic compounds. It is argued that the two different groups of chemicals (compounds occurring naturally in cuticular waxes vs pesticide molecules) were trapped in different fractions of wax during crystallization from the melt. The normal long‐chain aliphatic compounds appear to be incorporated into the crystalline fraction of the wax, while the cyclic pesticide molecules are confined to the solid amorphous regions. Our data indicate that constituents of cuticular waxes are not immobile. In fact, relatively small linear aliphatic molecules have mobilities that do not differ too much from those of cyclic pesticides. However, the pronounced size selectivity of diffusivities of long‐chain aliphatic compounds causes a rapid decrease in D with increasing chain length. The value of D of hexadecanoic acid was 3.81 × 10−18 m2 s−1 while that of dotriacontane was only 4.07 × 10−22 m2 s−1. Thus, increasing the carbon number by a factor of two resulted in a decrease in mobility by almost four orders of magnitude. Diffusivities of selected pesticide molecules in reconstituted wax were compared with permeances measured using intact barley leaves and were found to be in satisfactory agreement.
Persistence and activity of mexacarbate and its metabolites against spruce budworm larvae
Authors: Helson Blair V. , Sundaram K. M. Somu 
Published: November 2006

AbstractThis study was conducted to determine if metabolites of mexacarbate contribute to its residual toxicity to spruce budworm (Choristoneura fumiferana) larvae. Potted white spruce (Picea glauca) trees were treated with ‘Zectran’ UCZF # 19 at 100 g a.i. ha−1 and kept in a glasshouse. Mexacarbate residues declined by 98–99% within three days and reached non‐detectable levels 10 days after treatment. Mortality of larvae fed on buds from these trees declined more gradually and was still 19–27% when exposed 10 days after treatment. The very low levels of mexacarbate (<0.07 μg g−1) found after three days did not produce such mortality. Gas chromatographic analysis of metabolites in needles revealed that after three days, 4‐methylformamido‐3,5‐xylyl N‐methylcarbamate was present at levels 20–30 times higher than the parent compound. This metabolite was about 50 times less toxic than mexacarbate to larvae when applied topically but was only 7 times less toxic when ingested. Two other methylcarbamate metabolites, the amino, and methylamino analogues were detectable for one day following treatment but not at later time points. They were as toxic as mexacarbate both topically and orally. Based on these findings, the methylformamido analogue could contribute to the residual toxicity of mexacarbate treatments of spruce.
Ionization and sorption of fomesafen and atrazine by soils and soil constituents
Authors: Weber Jerome B. 
Published: November 2006

AbstractFomesafen exhibited weakly acidic properties and was titrated spectrophotometrically and determined to have a pKAof 3.0. [14C]fomesafen and [14C]atrazine, as references, were used in slurry‐type sorption studies with H+‐ and Ca2+‐saturated soil organic matter, Ca2+‐saturated montmorillonite clay, Norfolk sandy loan (Typic Paleudult) and Drummer silt loam (Typic Haplaquoll) at suspension pH values of 2.0 to 6.3. Sorption of atrazine was greater than that of fomesafen for the organic matter sorbents but similar for montmorillonite clay and the two soils. Sorption of both herbicides on the Drummer soil was much greater than on the Norfolk soil, due to the higher organic matter content of the former. Decreasing the suspension pH greatly increased sorption of both herbicides by all sorbents. Atrazine sorption was attributed to ionic bonding at low pH and physical bonding at neutral pH. Fomesafen sorption occurred by way of physical forces at near neutral pH and by way of hydrophobic bonding and/or precipitation at low pH. Mobility and bioavailability of the herbicides in soils is expected to be lower at low pH than at high or neutral pH.
Evidence for the enhanced biodegradation of napropamide in soil
Authors: Walker Allan , Parekh Nisha R. , Roberts Steven J. , Welch Sarah J. 
Published: November 2006

AbstractIn laboratory incubations, the time to 50% loss of napropamide was approximately 60; 21 and 8 days in soil treated for the first, second and third time respectively. In a survey of soils from commercial fields, there was evidence that enhanced biodegradation of the compound had been induced by normal field applications—in some soils by a single previous treatment. Confirmation of the observations of rapid rates of loss in pre‐treated soil was obtained in experiments with three formulations of napropamide. The rate of degradation in enhanced soils was unaffected by treatment of the soils with the antifungal antibiotic cycloheximide, but was inhibited by the antibacterial antibiotic chloramphenicol. Mixed bacterial cultures able to degrade the herbicide were obtained from three rapid‐degrading soils by enrichment culture. Isolates from two of them were able to degrade the herbicide in pure culture. These bacteria have, as yet, not been characterised.
Studies on a mixed bacterial culture from soil which degrades the herbicide linuron
Authors: Roberts Steven J. , Walker Allan , Parekh Nisha R. , Welch Sarah J. , Waddington Martin J. 
Published: November 2006

AbstractA stable mixed bacterial culture which degrades the herbicide linuron was isolated from soil by enrichment with linuron in a liquid mineral medium. Radio‐respirometry studies showed that the culture mineralised linuron completely. No intermediate degradation products were detected in the medium. The culture was able to utilise linuron as a source of both nitrogen and carbon and was also able to degrade the related herbicides monolinuron and chlorbromuron and the possible intermediate degradation products of linuron: 3,4‐dichlorophenyl‐l‐methylurea, 3,4‐dichlorophenylurea and 3,4‐dichloroaniline. The culture was unable to degrade the 1,1‐dimethyl substituted ureas monuron, diuron or metoxuron. The culture contained Gram‐negative aerobic rods, and Gram‐positive aerobic non‐spore‐forming rods and cocco‐bacilli. Of 124 isolates from the mixed culture, none degraded linuron in pure culture, indicating that a consortium of organisms is involved. Further investigation suggested that Pseudomonas spp. were important components of the population responsible for degradation.
Regulatory problems associated with natural products and biopesticides
Authors: Plimmer Jack R. 
Published: November 2006

AbstractFor registration, the United States Environmental Protection Agency (USEPA) separates pesticides into conventional chemical pesticides and biochemical and microbial pesticides. Natural products generally fall into the latter category. The USEPA has specified the test requirements for registration in the United States in the guidelines for registration of biorational pesticides (Subdivision M of 40 CFR Part 158).A discussion of the regulatory issues requires some reference to the accompanying scientific developments. The potential application of chemicals that affect insect behavior and development appeared an extremely promising approach to the reduction of adverse environmental and health impacts associated with many conventional pesticides. In addition to these benefits, the new biopesticides generally affected a very specific range of target species. However, although juvenile hormones and semiochemicals offer exciting new approaches to pest control, and are potentially valuable components of pest management strategies, acceptance of these techniques has been slow.Commercial development has been difficult for several reasons. Regulatory requirements may appear burdensome. Unconventional pest‐control technologies may call for special formulations or application equipment. It may not be easy to establish the efficacy of non‐lethal potential techniques. Investigators who derive funds from the public sector may have neither responsibility nor resources to carry the technology beyond the experimental stage. Because most activities in this field have been heavily research‐oriented, few workers have possessed the additional resources to obtain safety data or data to satisfy regulatory requirements.Difficulties in preparing and administering guidelines for registration of biopesticides lie in the novelty of the pest control agents and the diversity of the techniques involved in their effective use. Rapid advances in molecular biology and other disciplines continually strain the capabilities of regulators who are responsible for making safety assessments regarding pest‐control agents. Although regulatory authorities are familiar with conventional pesticides, safety assessment of biopesticides calls for totally different approaches.
Diversity of microbial products—discovery and application
Authors: Porter Neil , Fox Frances M. 
Published: November 2006

AbstractNatural products derived from micro‐organisms, plants and animals possess inherent biological properties and are, therefore, an excellent source of lead chemicals on which to base synthesis programmes employing rational design techniques. Only a fraction of the fungal kingdom has been screened systematically for novel metabolites despite their suspected potential. Moreover, the fungi are generally manipulable in laboratory culture systems and, because of their developmental versatility, they offer tremendous potential as sources of novel metabolites. Primary assay systems based on biochemical targets provide an effective means of screening microbial products; such assay systems also efficiently support chemical purification of lead activities and rapid elucidation of new chemical templates.