bluuebunny/crossref_metadata_2025 huggingface dataset:
The inhibition of chitin synthesis in spodoptera littoralis larvae by flufenoxuron, teflubenzuron and diflubenzuron
Authors: Clarke Barry S. , Jewess Philip J.
Published: November 2006

The chitin precursor [14C] N‐acetylglucosamine injected into the haemolymph of Spodoptera littoralis (Boisduval) larva was incorporated into the chitin exponentially with time. When caterpillars were injected with precursor at the commencement of feeding on acylurea‐treated leaf discs, flufenoxuron, teflubenzuron and diflubenzuron were found to be equally effective inhibitors of chitin synthesis, measured after 21 h. The dose response curves by feeding are not parallel, indicating that the relative potency of the compounds will vary across the dose range.

When chitin precursor was injected simultaneously with topically applied diflubenzuron, flufenoxuron or teflubenzuron, all three acylureas were found to be equally effective as inhibitors of chitin synthesis when measured after five hours. The I50values (50% inhibition of chitin synthesis) were not significantly different; average 600 ng, compared with LD50values (50% lethal dose) of ∼ 13 ng for flufenoxuron and teflubenzuron but 130 ng for diflubenzuron (topical application). Injection of precursor 24 h after topical application of insecticide gave an I50value which had dropped 670‐ and 150‐fold for flufenoxuron and teflubenzuron respectively but only 20‐fold for diflubenzuron. It is postulated that the reason for the low increase in diflubenzuron effectiveness with time was due either to less diflubenzuron than flufenoxuron reaching the site of action, or more probably, a faster rate of metabolism and excretion for diflubenzuron.

The lower toxicity of diflubenzuron compared with flufenoxuron and teflubenzuron may not be due to any inherent differences in biochemical effectiveness, but rather to different penetration/metabolism properties.
Activity of abamectin against larval stages of Spodoptera littoralis boisduval and Heliothis armigera hübner (Lepidoptera: Noctuidae) and possible mechanisms determining differential toxicity
Authors: Christie Paul T. , Wright Denis J.
Published: November 2006

Marked changes in the relative toxicity of topically‐applied abamectin were found between larval instars of Spodoptera littoralis, toxicity decreasing up to the fifth instar but increasing over 500‐fold (at LD50 level) in the sixth instar. By contrast, the toxicity of abamectin remained constant from fifth to sixth instar Heliothis armigera and there was an increase in the toxicity of two chemically unrelated insecticides, malathion (4‐fold) and lambda‐cyhalothrin (2.5‐fold), from fifth to sixth instar S. littoralis. Prior topical application or injection of the microsomal oxidase inhibitor, piperonyl butoxide (PB) increased the toxicity of abamectin (6–8 and 16‐fold respectively) against fifth instar S. littoralis, while topically‐applied PB increased the proportion of radioactivity present as abamectin in the ventral nerve cord of this instar following topical application with [3H]abamectin. Topically‐applied PB also enhanced the toxicity of abamectin against third (4‐fold) and fourth instar (5‐fold) S. littoralis but had no significant effect on sixth instar S. littoralis, fifth instar H. armigera, or on the toxicity of malathion and lambda‐cyhalothrin against fifth instar S. littoralis. Topical application of the esterase inhibitor, S,S,S‐tributyl phosphorothioate (DEF) significantly increased the toxicity of abamectin at the LD50 level (3‐fold) against fifth instar S. littoralis. The toxicity of injected abamectin against fifth instar S. littoralis was greater (20‐fold) than with topical application but injected abamectin was less toxic (2‐fold) against sixth instar S. littoralis and had no significant effect on fifth instar H. armigera. It is suggested that differential toxicity of abamectin is due in part to greater metabolism and reduced penetration in fifth instar S. littoralis than in sixth instar S. littoralis or fifth instar H. armigera.
Acidic isostere design: Synthetic strategies and recent progress in understanding electronic properties and metabolic stability
Authors: Lipinski Christopher A. , Chenard Bert L.
Published: November 2006

The efficient synthesis of a family of twelve acidic heterocycles of varying acidity from a single common intermediate facilitates the search for new acidic bioisosteres. An extension of this chemical approach led to a new family of phosphonate replacements in prototypes related to the N‐methyl Dasparate (NMDA) antagonist 2‐amino‐7‐phosphonoheptanoic acid (AP7). Acidic isostere design may be facilitated by grouping hydroxylic heterocyclic carboxylic isosteres into one of two electronic classes based on the Gandour hypothesis. The limitations of normal hydroxamic acids as carboxylic acid surrogates suggest that the excellent metabolic stability of reverse hydroxamic acids may be useful in prospective acidic isostere design.
Chemistry of sulfonylurea herbicides
Authors: Hay James V.
Published: November 2006

The discovery of the sulfonylurea class of herbicides is one of the most dramatic breakthroughs in herbicide research in several decades. Sulfonylureas possess unprecedented levels of herbicidal activity–as low as 1 g ha−1–very low mammalian toxicity, and very desirable environmental properties. This review will discuss the structure‐activity relationships of sulfonylureas, their physical and chemical properties, and their methods of synthesis.
Mode of action, crop selectivity, and soil relations of the sulfonylurea herbicides
Authors: Brown Hugh M.
Published: November 2006

The sulfonylurea herbicides are characterized by broad‐spectrum weed control at very low use rates (c. 2–75 g ha−1), good crop selectivity, and very low acute and chronic animal toxicity. This class of herbicides acts through inhibition of acetolactate synthase (EC 4.1.3.18; also known as acetohydroxyacid synthase), thereby blocking the biosynthesis of the branched‐chain amino acids valine, leucine and isoleucine. This inhibition leads to the rapid cessation of plant cell division and growth. Crop‐selective sulfonylurea herbicides have been commercialized for use in wheat, barley, rice, corn, soybeans and oilseed rape, with additional crop‐selective compounds in cotton, potatoes, and sugarbeet having been noted. Crop selectivity results from rapid metabolic inactivation of the herbicide in the tolerant crop. Under growth‐room conditions, metabolic half‐lives in tolerant crop plants range from 1–5 h, while sensitive plant species metabolize these herbicides much more slowly, with half‐lives > 20 h. Pathways by which sulfonylurea herbicides are inactivated among these plants include aryl and aliphatic hydroxylation followed by glucose conjugation, sulfonylurea bridge hydrolysis and sulfonamide bond cleavage, oxidative O‐demethylation and direct conjugation with (homo)glutathione. Sulfonylurea herbicides degrade in soil through a combination of bridge hydrolysis and microbial degradation. Hydrolysis is significantly faster under acidic (pH 5) than alkaline (pH 8) conditions, allowing the use of soil pH as a predictor of soil residual activity. Chemical and microbial processes combine to give typical field dissipation half‐lives of 1–6 weeks, depending on the soil type, location and compound. Very short residual sulfonylurea herbicides with enhanced susceptibility to hydrolysis (DPX‐L5300) and microbial degradation (thifensulfuron‐methyl) have been developed.
Structure‐activity relationships among the imidazolinone herbicides
Authors: Ladner David W.
Published: November 2006

The structure of the imidazolinone herbicides consists of three distinct moieties: the imidazolinone ring, the carboxylic acid and the backbone. The effect of changes in each of these on herbicidal activity, crop selectivity and AHAS enzyme inhibition has been studied. Though both whole‐plant and enzyme activity were drastically affected by changes in the carboxylic acid or imidazolinone ring portions of the molecule, a variety of backbones and of substituents on the backbones afforded good activity. Methyl‐isopropyl was found to be the best combination of substituents on the imidazolinone ring. While pyridine backbones generally gave the most active herbicides, benzene backbones led to the strongest enzyme inhibition. A QSAR study in the pyridine series generated two equations which proved useful for guiding the analog program toward the synthesis of potent heteropyridyl compounds. Selectivity in wheat is dependent upon differences in the rate of metabolism of key groups. Rapid metabolism of either the imidazolinone ring or backbone alkyl groups occurs rapidly in soybeans compared with susceptible weeds.
New herbicidal derivatives of 1,2,4‐triazolo [1,5‐a] pyrimidine
Authors: Kleschick William A. , Costales Mark J. , Dunbar Joseph E. , Meikle Richard W. , Monte William T. , Pearson Norman R. , Snider Sigrid W. , Vinogradoff Anna P.
Published: November 2006

Two new structural classes of herbicide have been discovered which are based on the 1,2,4‐triazolo[1,5‐a]pyrimidine ring system. These compounds are related to the known herbicidal sulfonylureas and imidazolinones and other studies have shown that they have a similar mode of action, involving the inhibition of branched‐chain amino acid biosynthesis, the site of action being the enzyme acetolactate synthase. The design, synthesis and structure‐ activity relationships of these new classes of compounds are described.
Mechanism of action of the 1,2,4‐triazolo[1,5‐a] pyrimidines
Authors: Gerwick B. Clifford , Subramanian Mani V. , Loney‐Gallant Vivian I. , Chandler Darrell P.
Published: November 2006

The substituted 1,2,4‐triazolo[1,5‐a]pyrimidines are a new class of highly active herbicides. Protection of Arabidopsis thaliana seedlings from triazolopyrimidine‐induced injury by the branched‐chain amino acids was observed. Acetolactate synthase (EC 4.1.3.18) was isolated and found to be quite sensitive to inhibition. I50 values for inhibition of the enzyme from a number of plant sources show little variation and no correlation to whole‐plant response, suggesting uptake, translocation and metabolism play key roles in modulating herbicidal activity. Further studies indicate that these chemicals are slow, tight‐binding inhibitors that are readily dissociated by gel filtration. Some correlations between in‐vitro activity and in‐vivo activity were observed for ortho‐substituted analogs on selected broadleaf species.
Leaching potential and decomposition of fluroxypyr in Swedish soils under field conditions
Authors: Bergström Lars F. , McGibbon Alec S. , Day Steve R. , Snel Marten
Published: November 2006

The mobility and decomposition of the herbicide fluroxypyr (4‐amino‐3,5‐dichloro‐6‐fluoro‐2‐pyridyloxyacetic acid) was studied under field conditions in a sandy soil and a clay soil. Leachate was collected in lysimeters with undisturbed soil (sand) and in tile‐drained plots (clay). Soil samples to a depth of one metre were also collected in both soils to characterize the temporal depth distribution of fluroxypyr in the profiles. The herbicide was applied as the I‐methylheptyl ester of fluroxypyr at two rates, 187.5 and 375.0 g a.e. ha−1, representing the normal and double the dose of the compound used for spring cereals. Some lysimeters received supplementary watering. Only two leachate samples (one from each soil) had concentrations of fluroxypyr above the detection limit (1 μg litre−1), i.e. 2 and 5 μg litre−1. Both samples were collected within two months after application, when less than 2 mm of drainage had been collected. The methylheptyl ester of fluroxypyr was not found in any of the samples. Fluroxypyr levels above the detection limit in soil (5 μg kg−1 dry soil), were never found below the topsoil (0.2 m) in the clay profile, while, in the sandy profile, levels just above the detection limit were found occasionally in deeper soil layers. Concentrations were reduced to undetectable or very low levels within three months after spraying.
Degradation of pendimethalin by soil fungi
Authors: Barua Atri S. , Saha Jayanta , Chaudhuri Subhendu , Chowdhury Ashim , Adityachaudhury Narayan
Published: November 2006

Several soil fungi, Aspergillus flavus, A. terreus, Fusarium solani, F. oxysporum, Penicillium citrinum and P. simplicissimum effectively degrade pendimethalin [N‐(I‐ethylpropyl)‐2,6‐dinitro‐3,4‐xylidine] supplied as sole carbon source in mineral solution. Degradation of pendimethalin by F. solani resulted in the isolation and identification of N‐propyl‐3‐methyl‐4‐hydroxy‐2,6‐dinitroaniline, N‐(I‐ethylpropyl)‐2‐amino‐6‐nitro‐3,4‐xylidine and 2,6‐dinitro‐3,4‐xylidine. The partial pathways involved in the degradation of pendimethalin have also been proposed.
An evaluation of the herbicidal and plant growth regulatory activity of a novel class of carbohydrate‐derived 6,8‐dioxabicyclo[3.2.1]octanes
Authors: Henzell Ronald F. , Furneaux Richard H. , Tyler Peter C.
Published: November 2006

Thirty‐five carbohydrate‐derived dioxabicyclo[3.2.l]octane derivatives have been tested for herbicidal and plant growth regulatory (PGR) activity in an Arabidopsis thaliana assay. Nine of these were herbicidal at concentrations of ⩽ 16 μg ml−1 in the growth medium. Three compounds, viz, 1,6‐anhydro‐3‐deoxy‐4‐O‐(2,6‐dichlorobenzyl)‐2‐O‐methyl‐β‐D‐ribo‐hexopyranose(I), its 4‐O‐benzyl analogue (II), and l,6‐anhydro‐2‐azido‐4‐O‐benzyl‐2,3‐dideoxy‐β‐D‐ribo‐hexopyranose (III) were very active herbicides, killing plants by the rosette stage at 1 μg ml−1 or less. At lower rates, the herbicides acted as growth regulators, reducing growth rates of shoots and roots as well as flowering and seed‐pod development. A further 14 compounds exerted PGR effects only, while 12 compounds were virtually inactive at 16 μg ml−1, the highest rate tested. The ability of the active compounds to reduce seed viability on mature plants at sublethal concentrations was demonstrated in four cases.
Predicting pesticide percutaneous penetration
Authors: Hadgraft Jonathan , Brain Keith R.
Published: November 2006

It is important to be able to predict the absorption of materials through the skin, particularly if there are toxicological implications. However, for pesticides which are known to be toxic, there are ethical considerations in conducting in‐vivo human evaluations of percutaneous absorption. It would therefore be desirable to obtain an indication of the amount of pesticide that can penetrate the skin from a simple knowledge of its physico‐chemical properties. It has been shown that the rate of penetration of a range of drugs through intact skin can be estimated from parameters such as partition coefficient, molecular size and solubility. These parameters will be equally applicable to pesticides and the relevant mathematical expressions are discussed.
Review—mechanism of action of herbicidal and fungicidal compounds on cell membranes
Authors: Burden Raymond S. , Cooke David T. , Hargreaves John A.
Published: November 2006

The eukaryotic cell membrane is thought to consist of a mobile bilayer of phospholipid, sometimes intercalated with sterols, in which peripheral and transmembrane proteins are embedded. This provides a model whereby the mode of action of many fungicidal and herbicidal compounds can be rationalised and understood. Some compounds, such as the polyene antibiotics, steroidal saponins and certain phytoalexins, induce membrane malfunction by direct insertion, often complexing with vital components. Others, such as paraquat and the nitrodiphenyl ether herbicides, cause membrane damage by inducing lipid peroxidations. Furthermore, there are many compounds, including the sterol‐biosynthesis‐inhibiting fungicides and the aryloxyphenoxypropionate and cyclohexanedione herbicides, which interfere with the biosynthesis of membrane components. Because membrane structure is fundamentally similar in eukaryotes, it is important to discover the reasons for any differential toxicity displayed by these compounds and, if necessary, to find ways of optimising desirable patterns of selectivity.
Chitin biosynthesis inhibition and fungicidal effect of thiosemicarbazones of 2‐formyl‐ and 2‐acetylpyridine, their hydrogenated derivatives and copper complexes thereof
Authors: Wengel Anita , Jacobsen Niels , Kolind‐Andersen Hans , Bjerregaard Poul
Published: November 2006

Several thiosemicarbazones of 2‐formyl‐ and 2‐acetylpyridine dialkylated on N4 and non‐alkylated on N2 were found to be broad‐spectrum protectant fungicides with activity particularly against oomycetes. The effect of some of the compounds on chitin biosynthesis was studied, but the low inhibitory activity observed combined with the fungicidal activity spectrum—particularly the high activity against oomycetes—excludes this as their main mode of action. Attempts at enhancing the systemic properties of the compounds by chemical modifications failed.
Effect of 4‐amino‐6‐methyl‐3‐phenylamino‐1,2,4‐triazin‐5(4H)‐one on the integrity of chloroplasts from barley leaves
Authors: Muñoz Romualdo , Martínez‐Martínez Antonio , Ros‐Barceló Alfonso , Pedreño M. Angeles
Published: November 2006

4‐Amino‐6‐methyl‐3‐phenylamino‐1,2,4‐triazin‐5(4H)‐one alters the integrity of chloroplasts in barley (Hordeum vulgare L. var. Hassan) leaves as judged by their sedimentation profiles in linear gradients of sucrose. This effect may be related to the inhibition caused by 4‐amino‐6‐methyl‐3‐phenylamino‐1,2,4‐triazine‐5(4H)‐one of both ascorbate peroxidase and superoxide dismutase activities, and could thus be explained by an accumulation of toxic reduced‐oxygen species in illuminated chloroplasts.
Synthesis and structure‐activity relationships of 1‐aryl‐4‐substituted‐1,4‐dihydro‐5H‐tetrazol‐5‐ones, a novel class of pre‐ and post‐emergence herbicides
Authors: Theodoridis George , Hotzman Frederick W. , Scherer Lynn W. , Smith Bruce A. , Tymonko John M. , Wyle Michael J.
Published: November 2006

L‐Aryl‐4‐substituted‐1,4‐dihydro‐5H‐tetrazol‐5‐ones (I) represent a new class of herbicides, which, when applied pre‐ or post‐emergence in the presence of light, control several agriculturally important weed species. Forty‐eight analogues have been synthesized and their herbicidal activities determined in order to study structure‐activity relationships. In general, these compounds demonstrated: (l) optimum herbicidal activity when the 4‐ substituent on the tetrazole ring was – CH2CH2CH2F, and the aryl group 2‐ fluoro‐4‐chloro‐5‐substituted phenyl; (2) optimum herbicidal activity over a broad spectrum of grass and broad leaf weeds, with marginal crop selectivity when the C5 substituent on the phenyl group was – OCH2CCH; and (3) a high degree of selectivity on several major crops and primarily broadleaf weed control when this substituent was – NHSO2CH2CH3.
The synthesis and fungicidal activity of a series of 1‐aryltetrazole‐5‐sulphones
Authors: Richards Ian C. , Thomas Peter S.
Published: November 2006

The synthesis and fungicidal activity of a series of l‐aryltetrazole‐5‐sulphones are reported. Their activity against Plasmopara viticola is described. It is proposed that the compounds act as general electrophiles. Structure‐activity relationships are discussed in broad terms.
Direct and indirect effects of four herbicides on the activity of carabid beetles (coleoptera: Carabidae)
Authors: Brust Gerald E.
Published: November 2006

Four herbicides, atrazine, simazine, paraquat, and glyphosate were tested for their acute and chronic toxicity as well as repellent effects on five common carabid beetles (Amara sp., Agonum sp., Pterostichus sp., Anisodactylus sp., and Harpalus sp.) in laboratory and greenhouse experiments. These carabid species are potential biocontrol agents and interference with their biology through herbicide applications, either directly or indirectly, could lead to soil pest outbreaks. Short‐term field studies also were conducted to verify laboratory and greenhouse results. The four herbicides did not have significant acute or chronic effects on male or female carabid longevity or food consumption during one year after exposure to initial field‐rate applications. Only simazine and atrazine had a repellent effect on carabids, which lasted approximately three days in greenhouse studies. Behavioral studies indicate that once carabids, especially smaller ones (< 10 mm in length), establish burrows and foraging territories, they tend to remain in these areas and migrate out of them only slowly. There was no toxic or repellent effect of any herbicide in the field. Carabids, instead, apparently responded to the destruction of plant material which provided a less favorable habitat for the larger (> 10 mm length) carabids. Glyphosate and paraquat had the greatest effect on carabids by the second week in field studies, with significantly fewer large carabids found in these two treatments than in the control. Large carabids did not return to paraquat‐ and glyphosate‐treated field areas until approximately 28 days after application; consequently, lower rates of predation of early‐season lepidopteran pests by these carabid species may occur in no‐tillage corn fields that utilize herbicides for weed control.
The role of protoporphyrin IX in the mechanism of action of diphenyl ether herbicides
Authors: Duke Stephen O. , Becerril José M. , Sherman T. D. , Lydon John , Matsumoto Hiroshi
Published: November 2006

Photobleaching diphenyl ether, cyclic imide and oxadiazole herbicides inhibit protoporphyrinogen oxidase (Protox), resulting in uncontrolled, non‐enzymic oxidation of accumulated protoporphyrinogen to protoporphyrin IX (Proto). Proto accumulation is stimulated by deregulation of the porphoyrin pathway due to blockage of heme synthesis. Heme is a Proto product and a feedback inhibitor of δ‐aminolevulinic acid synthesis. Strong correlations were found in several species under various conditions (e.g. sprayed on intact plants or taken up by leaf dises) between the accumulation of Proto and the degree of herbicidal damage caused by these herbicides. Levels of protochlorophyllide, Mg‐Proto, or Mg‐Proto monomethyl ester did not correlate significantly with herbicidal damage. Kinetic data indicated that elevated levels of protochlorophyllide in tissues treated with these herbicides only occurred after Proto had accumulated to high levels. Thus, Proto apparently re‐enters the porphyrin pathway to a significant extent after other cellular sites are saturated. Fluorescence microscopy indicated that considerable amounts of Proto accumulated outside the plastid in herbicide‐treated cells. All of the data were consistent with the hypothesis that Proto plays a critical role as a photosensitizing pigment in the mode of action of Protox‐inhibiting herbicides and that chlorophyll precursors that are derivatives of Proto are not significantly involved in the mode of action of these herbicides.
Photodynamic herbicides VIII. Mandatory requirement of light for the induction of protoporphyrin IX accumulation in acifluorfen‐treated cucumber
Authors: Nandihalli Ujjanagouda B. , Liebl Rex A. , Rebeiz Constantin A.
Published: November 2006

It is shown that continuous illumination is mandatory for the induction of tetrapyrrole accumulation in acifluorfen‐sodium‐treated plants and for the photosensitization of tetrapyrrole‐dependent photodynamic damage. At low concentrations of acifluorfen‐sodium (up to 20 μM), photoporphyrin IX appears to be the major light‐induced tetrapyrrole that accumulates in the treated plants. At higher concentrations of acifluorfen‐sodium, monovinyl chlorophyllide a accumulates in addition to protoporphyrin IX. In the light, the development of photodynamic injury appears to be directly related to the accumulation of the light‐induced tetrapyrroles. For example when acifluorfen‐sodium‐treated plants are returned to darkness, or are treated with tetrapyrrole biosynthesis inhibitors, tetrapyrrole accumulation and photodynamic injury come to a halt. In‐vivo and in‐organello studies failed, however, to support the commonly held hypothesis that the induction of tetrapyrrole accumulation in the light, in acifluorfen‐sodium‐treated plants, is only dependent on the inhibition of protoporphyrinogen oxidase. Indeed, when plastids capable of very high rates of tetrapyrrole biosynthesis and accumulation were incubated with δ‐aminolevulinic acid and acifluorfen‐sodium, either in darkness or in the light, a severe inhibition of protoporphyrin IX and total terapyrrole formation was observed. Althoung these results are compatible with the inhibition of tetrapyrrole formation by acifluorfensodium at the level of protoporphyrinogen oxidase, they indicate that, in addition to that inhibition, other cuellular processes are probably involved in the light‐dependent accumulation of protoporphyrin IX in acifluorfensodium‐treated plants.
Evaluation of dicarboximide residues in cold‐stored grapes exposed to field and post‐harvest treatments
Authors: Scrano Laura , Faretra Franco , Cariddi Corrado , Antonacci Emmanuele , Bufo Sabino A.
Published: November 2006

Dicarboximide fungicides were used in field treatments as well as in post‐harvest fumigations on cold‐stored table grapes. They proved to be highly effective against gray mould, a major disease during storage or transport of grapes, and a valuable alternative to sulphur dioxide within one month after harvesting.

Residues of the fungicides were determined through gas‐chromatographic analysis on grapes field‐sprayed with dichlozolinate, iprodione, procymidone or vinclozolin, and on grapes exposed to post‐harvest treatments with new smoke formulations of procymidone and vinclozolin. In most cases, residue levels were lower than those allowed by Italian sanitary laws. Post‐harvest fumigations caused only a slight increase of residue levels as compared to field applications.
Deamination of metribuzin in tolerant and susceptible soybean (Glycine max) cultivars
Authors: Fedtke Carl
Published: November 2006

The deamination of metribuzin was studied in vitro in peroxisomes isolated from the leaves of soybean cultivars which were either metribuzin tolerant, intermediate, or sensitive. The deamination rate observed with peroxisomes from tolerant leaves was about twice the rate observed with peroxisomes from sensitive leaves. The intermediate group was also intermediate with respect to the in‐vitro deamination rate.

Tolerant and sensitive intact soybean plants were pulse‐labeled with [14C]metribuzin via the roots for 5 h. The extractable radioactivity in roots, stems and leaves was measured and separated into metabolites after the 5 h pulse and after an additional 24 h growth in water. The level of DA (deaminated metribuzin) was always significantly higher in the stems and leaves of tolerant soybean plants (4.8–10.0% of the extracted radioactivity) than in sensitive stems and leaves (1.8–2.9%). Conjugates were rapidly formed in tolerant as well as in sensitive soybean tissues. More conjugates were found in the tolerant cultivars, especially after the 5 + 24 h incubation time.

Labeled [14C]DA fed to soybean plants via the roots was conjugated two to four times faster than [14C]metribuzin. Tolerant soybean tissue conjugated [14C] DA two to three times faster than sensitive tissue. The results are interpreted as showing that, in tolerant soybean plants, metribuzin is metabolized via deamination and subsequent conjugation, in addition to the well‐known direct conjugation of metribuzin parent compound.
Distribution and metabolism of abamectin in larval stages of Spodoptera littoralis boisduval and Heliothis armigera hübner (Lepidoptera: Noctuidae)
Authors: Christie Paul T. , Wright Denis J.
Published: November 2006

Comparisons were made between the amounts of abamectin and total radioactivity recovered from Spodoptera littoralis and Heliothis armigera larvae after topical application of [3H]abamectin. Penetration (as shown by wash‐off experiments) did not differ significantly between the Spodoptera instars. Significantly more abamectin was recovered from ventral nerve cord samples of larvae showing symptoms of poisoning than from larvae not showing these symptoms. Fifth‐instar S. littoralis larvae had a significantly lower proportion of radioactivity as abamectin in the ventral nerve cord than in sixth‐instar S. littoralis or fifth‐ and sixth‐instar H. armigera. The proportion of radioactivity present as abamectin (but not total radioactivity) was significantly increased when the fifth‐instar S. littoralis larvae were pre‐treated with piperonyl butoxide (PB) suggesting that the relative insensitivity of fifth‐instar S. littoralis larvae to abamectin is due at least in part to greater metabolism, particularly by microsomal oxidases. Fat body samples consistently had a greater proportion of radioactivity as abamectin than the nerve cord and the former may act as storage sites for abamectin.
Mode of action of herbicidal ALS‐inhibitors on acetolactate synthase from green plant cell cultures, yeast, and Escherichia coli
Authors: Babczinski Peter , Zelinski Thomas
Published: November 2006

Inhibitors of branched‐chain amino acid biosynthesis—by inhibiting acetolactate synthase (ALS)—represent the most active group of herbicidal compounds to date (Shaner, D.L., Recent Adv. Phytochem. 23 (1989) 227–61). A microbial screening technique has been developed to investigate known and possible new ALS‐inhibitors. Escherichia coli mutant FD 1062, which expresses only valine‐resistant ALS II isoenzyme as the solely branched‐chain amino acid synthesizing isoenzyme, has been used extensively to optimize known and to screen for new chemical classes of ALS‐inhibitors, respectively. Herbicidal compounds like sulfonylureas, triazolopyrimidines, pyrimidylsalicylates, carbamoylpyrazolines, sulfonylimino‐azinyl‐heteroazoles, sulfonylamide azines, and substituted sulfonyldiamides, respectively, are active on minimal medium with Ki‐values which resemble the rank order of biological activity of these compounds in the greenhouse. Interestingly, herbicidal imidazolinones are not at all inhibitory on E.coli strain FD 1062 in vivo although, of course, they exert high activity on isolated bacterial ALS. Similarly, N‐protected valylanilides, pyrimidyl mandelic acids, benzenesulfonyl carboxamides, and uhiquinone‐O are inactive in the bacterial assay but have been shown by other methods to act as ALS inhibitors. Additionally, reversal experiments can he performed to exclude, e.g. artificial inhibitory effects of test compounds. Moreover, a thin‐layer biogram application technique opens the opportunity to test mixtures of chemicals.

From green plant cell cultures (Catharanthus roseus) ALS has been isolated and characterized in terms of inhibition by sulfonylureas, imidazolonones, triazolopyrmidines, salicylated, and carbamoylpyrazolines, imidazolinones, triaiolopyritnidines, salicjdates, and carbarnoylpj˜razolines,
respectively. All five types show biphasic slow tight binding kinetics with
Stedy state I50values of 0.5 nm (sulforneturon), 1.9 nm (triazolopjirimidine),
8.3 nm (salicylate), 23 nm (imazapyr), and 135 nm (carbamoylpyrazoline),respectiuely .

Isolated ALS from Saccharomyces cerevisiae is equallv well blocked by
herbicidal ALS inhibitors although with different I50values ( triazoiopyrimidine, 21 nm, sulforneturon, 70 nm, salicylate, 21 μm, imaiapyr, 38μm, and carbamoylpyrazoline, 148 μm ). Surprisingly, biphasic kinetics could not be observed with the yeast enzjtme although slow binding hehauiour was clearly established.
Exprimental assessment of pesticide leaching using undisturbed lysimeters
Authors: Kördel Werner , Herrchen Monika , Klein Werner
Published: November 2006

Outdoor lysimeter experiments are integrated studies, which consider the comprehensive influence of environmental variables on the mobility and fate in soil of a chemical and its plant uptake, and give valid information on its potential for groundwater contamination. The interpretation of the studies has to consider:

that migration behaviour under environmental conditions does not correspond with ‘ideal chromatographic behaviour’ and

that lysimeter studies include the variables of field experiments and are not fully standardized. The results of lysimeter studies on chloethocarb and bentazone are discussed.
The chemistry and biological activity of a new class of azole fungicides: 1‐amino‐1,2,4‐triazoles
Authors: Basarab Gregory S. , Pifferitti Michael , Bolinski Martha M.
Published: November 2006

The fungicidal activity of a novel class of triazole compounds in which the 1‐position of the azole nucleus is bonded to a nitrogen atom was investigated. Such 1‐amino‐1,2,4‐triazoles are amenable to great structural variation which allows the elucidation of the requirements for biological activity. As in most other triazole fungicides, the basic structural requirement for activity is a two‐atom bridge connecting the azole nucleus to a hydrophobic group, typically an aromatic ring. The synthesis and optimization of fungicidal activity of this class of triazole fungicide are discussed.
Synthesis of 1,2,4‐triazole compounds related to the fungicides flutriafol and hexaconazole
Authors: Worthington Paul A.
Published: November 2006

Triazole and imidazole compounds are important both as pharmaceutical and agrochemical fungicides. It has been demonstrated that they exhibit this activity because they inhibit the 14 α‐demethylase enzyme involved in the biosynthesis of fungal sterols. A knowledge of the mode of action of the triazoles paclobutrazol, diclobutrazol and propiconazole has made it possible to devise inhibitors of the 14 α‐demethylase enzyme somewhat more readily, using computer graphic techniques. These techniques were used in the discovery of flutriafol, one of the first examples of a triazole tertiary alcohol structure. They also assisted in identifying other triazole tertiary alcohol structures for testing as fungicides. Hexaconazole is one example of a highly active broad‐spectrum fungicide. Modification of the hexaconazole structure has produced many other active fungicides, many of which can be conveniently synthesised by the addition of organometallic (e.g. lithium, magnesium, aluminium, titanium or zinc) reagents to α‐1,2,4‐triazol‐1‐yl ketones or α‐haloketones. Alternatively, they can be prepared by the reaction of nucleophiles such as mercaptans, nitrogen heterocycles or organometallic (e.g. magnesium) reagents with epoxides.
Chemistry and biology of novel amine fungicides: Attempts to improve the antifungal activity of fenpropimorph
Authors: Akers Alan , Ammermann Eberhard , Buschmann Ernst , Götz Norbert , Himmele Walter , Lorenz Gisela , Pommer Ernst‐Heinrich , Rentzea Costin , Röhl Franz , Siegel Hardo , Zipperer Bernhard , Sauter Hubert , Zipplies Matthias
Published: November 2006

In spite of considerable efforts by many workers, there has been a lack of progress in the area of amine fungicides since fenpropimorph. Random synthesis of a large variety of different amine compounds, as well as intelligent structural modification of the lead structure fenpropimorph (well over 15 000 amines have been screened at BASF alone) have not led to a new market product so far. Further work has been focused on the reported mode of action of fenpropimorph, notably on the inhibition of the sterol Δ14‐reductase. Although some doubt has to be cast on the hypothesis that fenpropimorph behaves as a sterol mimic, the concept of ‘high energy intermediate’ inhibitors has been employed successfully. Rational drug design of azasterol mimics has led to a number of very potent inhibitors of the sterol Δ14‐reductase which also displayed high fungicidal activity in the greenhouse. Although many of these compounds are more powerful reductase inhibitors than fenpropimorph, under field conditions none showed significant advantages over this established fungicide.

Most likely, fenpropimorph already exhibits the maximum fungicidal activity which can be attained by blocking the sterol Δ14‐reductase. This would mean that, with the development of the ‘second generation’ amine fungicide fenpropimorph, this class of compounds has already virtually been optimized.
Synthesis of a new class of pyridine herbicide
Authors: Lee Len F. , Stikes Gina L. , Sing Larry Y. L. , Miller Maria L. , Dolson Mark G. , Normansell Jean E. , Auinbauh Susan M.
Published: November 2006

A new class of fluoroalkylated pyridine herbicides has been discovered. The 3,5‐pyridinedicarboxylates are prepared either from ethyl 4,4,4‐trifluoroacetoacetate via Hantzsch dihydropyridine synthesis or from trifluoroacetonitrile via cyclocondensation and carboxylation. Hydrolysis of the ester groups, followed by derivatization of the resulting acids yields a variety of herbicidally active analogs including ester, thioester, amide, halogen, amino, alkoxy and alkylthio derivatives.
Photolysis of acifluorfen in aqueous solution
Authors: Pusino Alba , Gessa Carlo
Published: November 2006

The photolysis of acifluorfen, sodium 5‐[2‐chloro‐4‐(trifluoromethyl)‐phenoxy]‐2‐nitrobenzoate (I) in aqueous solution afforded only 2‐chloro‐1‐(4‐nitrophenoxy)‐4‐trifluoromethylbenzene (II) arising from photodecarboxylation. The reaction followed first‐order kinetics, though the photo‐reaction rate was solvent‐dependent. A mechanism that accounts for the formation of the product is proposed.
Insecticide resistance in the bollworm, Helicoverpa armigera from Indonesia
Authors: McCaffery Alan R. , Walker Andrew J. , Topper Clive P.
Published: November 2006

Helicoverpa armigera collected from cotton growing areas of South Sulawesi, Indonesia in 1987 and early 1988 were resistant to cypermethrin. It is suggested that the 86‐fold resistance to cis‐cypermethrin in 1987 and the 65‐fold resistance to cis/trans‐cypermethrin in 1988 are consistent with this being a major cause of failure to control the insects in cotton in this area. The second laboratory generation showed a 20‐fold resistance to fenvalerate. The larvae collected in 1988 additionally had a 203‐fold resistance to DDT and a 5.6‐fold resistance to endosulfan. The results are discussed in relation to the fact that this is a further region in which Helicoverpa armigera has developed resistance to a number of pyrethroids.
A barn owl feeding study with [14c]flocoumafen‐dosed mice: Validation of a non‐invasive method of monitoring exposure of barn owls to anticoagulant rodenticides in their prey
Authors: Eadsforth Charles V. , Dutton Alan J. , Harrison Elizabeth G. , Vaughan John A.
Published: November 2006

A study was carried out to assess the feasibility of monitoring the exposure of barn owls (Tyto alba) to an anticoagulant rodenticide, flocoumafen, by analysis of residues in regurgitated pellets following consumption of flocoumafen‐contaminated mice. Mice were fed on a diet containing [14C]flocoumafen, equivalent to 12 mg kg−1, and killed 24 h later. A single [14C]flocoumafen‐contaminated mouse was fed to each of four captive barn owls, equivalent to 0·11‐0·23 mg kg−1 per bird, followed on seven successive days by control diet (i.e. undosed mice). The [14C]flocoumafen dose was eliminated by the owls over the eight‐day period in pellets (44%, range 35–55%) and faeces (18%, range 11–21%), with the highest residues being observed in samples from the first 24‐h period. Further detailed analysis of the pellets confirmed that flocoumafen residues in the first‐day pellets represented 15% (range 8–26%) of the original flocoumafen residues ingested by the barn owls. Calculations based on these data and typical flocoumafen residues in live captured rodents (following baiting) confirm that pellet residue analysis is a sensitive and appropriate method for the non‐invasive monitoring of exposure of barn owls to flocoumafen. There were no symptoms of anticoagulant poisoning in any of the birds; two of the birds were successfully paired the next season and produced fledgelings.
Organophosphorus insecticide residues in virgin Greek olive oil, 1988–1990
Authors: Lentza‐Rizos Chaido , Avramides Elizabeth J.
Published: November 2006

Organophosphorus insecticide residues have been monitored for two years in virgin olive oil after dimethoate and fenthion treatments to control the olive fruit fly. No dimethoate residues were detected in any of the samples. For the first and second years, 50% and 21%, respectively, of the samples contained no detectable fenthion residues, while 4% and 6%, respectively had residue concentrations exceeding the Codex Alimentarious Maximum Residue Limit (1 mg kg−1). The mean concentration was 0·236 mg kg−1 oil and the estimated daily intake of fenthion 0·0002 mg kg−1 body weight (Acceptable Daily Intake 0·001 mg kg−1 body weight). The parent compound was the most important residue in fresh samples, while aged samples contained a higher amount of the metabolite fenthion sulfoxide. The contribution of the oxygen analogues (P= 0 metabolites) of fenthion to the total residue concentration was<5% in most cases.
Resistance risk assessment of two insect development inhibitors, diflubenzuron and cyromazine, for control of the housefly Musca domestica. part i: Larvicidal tests with insecticide‐resistant laboratory and danish field populations
Authors: Keiding Johannes , Jespersen Jørgen B. , El‐Khodary Ahmed S.
Published: November 2006

Larvicide tests with diflubenzuron (DFB) and cyromazine (CYR) were carried out against 15 laboratory housefly strains and 89 field strains collected from 87 Danish and 2 Swedish farms, 1975–89. The strains represented a wide range of adult insecticide resistance and R‐mechanisms.

The larvicide tests were done by treating larval medium with serial or discriminating dosages of the larvicide, seeding it with eggs and calculating the mortality during development to adults. The WHO susceptible strain (S) was used as a reference.

Dose‐response tests with DFB gave resistance ratios (R/S) from 1·1 to 4·1 at LC50 and 0·3 to 3·4 at LC95 and, with CYR, R/S from 0·6 to 1·8 at LC50 and 0·6 to 2·9 at LC95.

It was concluded that the relatively small variation in susceptibility between strains was not generally correlated with resistance in adult flies to organophosphorus, pyrethroid or other conventional insecticides (neurotoxins).

Tests with discriminating dosages of DFB (59 farms) and CYR (63 farms) showed no indication of resistance to either product.

The results of investigations by other workers on the relation between resistance to DFB or CYR and resistance to conventional insecticides are discussed.
Factors affecting the performance and crop phytotoxicity of a new rice herbicide, cinmethylin. I. Effects of water depth and soil type on the distribution and uptake of cinmethylin by transplanted and direct‐seeded rice
Authors: Terence Grayson B. , Webb James D.
Published: November 2006

Following successful glasshouse evaluation, first‐year field trials showed that cinmethylin could give excellent control of barnyard grass (Echinochloa crus‐galli) in rice paddies. However, for the successful development of a herbicide in rice, a thorough understanding of its distribution over time between water, soil and plants as affected by water depth and soil type is necessary.

An application of an emulsifiable concentrate formulation to laboratory paddies containing transplanted rice showed that more of the cinmethylin became associated with and moved into the soil of shallow paddies than in the more usual deep paddies. After the first day this resulted in slightly higher concentrations of cinmethylin being accumulated by the apical meristem, the site of action of cinmethylin, in shallow‐paddy plants and explains the higher phytotoxicities observed in this situation. Rapid removal of cinmethylin by the soil from the paddy water could reduce that available for absorption by the apical meristem of barnyard grass, just below the water surface, and might result in poorer control of this weed. Deeper paddies are therefore recommended for the use of cinmethylin in transplanted rice.

An experiment involving direct‐seeded rice confirmed that a decrease in paddy water depth and higher organic‐matter soils increased the association of cinmethylin with the paddy soil. Thus paddy‐water concentrations and availabilities of cinmethylin to various parts of plants were influenced by water depth and soil type. In contrast to transplanted rice, the apical meristem of direct‐seeded rice is submerged in the paddy water and the stem concentrations of cinmethylin were then generally correlated with the paddy‐water concentrations. They were highest from the shallow, sandy paddies and lowest from the deep, silt clay loam paddies. These relative concentrations correlate with observed relative phytotoxicities of direct‐seeded rice, activities against barnyard grass and the narrower selectivity margins between the weeds and the direct‐seeded crop.

The cinmethylin concentrations in the apical meristems of the transplanted rice were always lower than those from the direct‐seeded rice and give an illustration of a classical case of depth protection' of a crop from an applied herbicide.
Study on rare‐earth complexes of mixed amino‐acids (MAR) in controlling disease and stimulating growth of wheat
Authors: Li Zhichang , Liu Chiqing , Xu Younglin , Liu Dengmin
Published: November 2006

MAR is a rare‐earth complex of mixed amino‐acids which was recently synthesized in the similar way to homodemycine. Five‐year field trials have proved that MAR not only stimulates crop growth and increases crop yield but also effectively controls stripe rust of wheat, and upgrades the quality of crops. This paper describes the results of the application of MAR in controlling disease and stimulating growth of wheat.
Evaluation of permethrin for the protection of cattle against mosquitoes (diptera: Culicidae), applied as electrostatic and low pressure sprays
Authors: Shemanchuk Joseph A. , Spooner Roy W. , Golsteyn Lorraine R.
Published: November 2006

Permethrin was tested for the protection of cattle against field populations of mosquitoes. Permethrin (500 ml of a permethrin 4·0 g liter−1 aqueous emulsion) applied with a ‘Dual‐Cloud’ electrostatic sprayer was effective in providing coverage of the cattle body surface of a group of four animals; 100 ml of a permethrin 5·0 g liter−1 aqueous emulsion applied with a ‘Dual‐Cloud'’ electrostatic sprayer as a total body spray to a yearling heifer provided 70% or better protection from field populations of mosquitoes for at least 72 h; 500 ml of a permethrin 1·0 g liter−1 aqueous emulsion applied as a low‐pressure spray to the body of a yearling heifer provided 70% or better protection from mosquitoes for at least 140 h. Permethrin applied as a total body‐spray thus provides adequate protection to cattle from field populations of mosquitoes.
Adsorption‐leaching study of the herbicides metamitron and chloridazon
Authors: AráNzazu Goicolea M. , Arranz Juan F. , Barrio Ramón J. , de Balugera Zuriñe Gómez
Published: November 2006

Freundlich isotherms were obtained for the adsorption equilibrium of the herbicides metamitron and chloridazon with the components of a representative soil in a pesticide concentration range of 10‐1000 γg ml−1 for metamitron and 10‐500 μg ml−1 for chloridazon.

The mobility of these herbicides through soil columns was also studied using the displacement technique described by Davidson (Soil Sci. Soc. Amer. Proc., 32 (1968) 629). The experiment was carried out simultaneously in three columns, two of which were fed with solutions of the herbicides while the third was used as a control. The herbicide solutions flowed down by gravity and were collected at the outlet at different times. The herbicide content of these outlet solutions was determined by Differential Pulse Polarography.