bluuebunny/crossref_metadata_2025 huggingface dataset:
Pesticide effects on secondary metabolism of higher plants
Authors: Lydon John , Duke Stephen O.
Published: November 2006

Secondary compounds serve both endogenous and exogenous functions in higher plants because they are involved in plant growth and development as well as intraspecies and interspecies interactions. Documentation of the effects of pesticides on secondary compound biosynthesis in higher plants is increasing. While several herbicides have been reported to reduce levels of secondary compounds by non‐specific mechanisms, a few herbicides, such as alachlor and glyphosate, directly affect specific biosynthetic steps. Alachlor reduces flavonoid synthesis at a step late in the biosynthetic pathway, and glyphosate blocks synthesis of all cinnamate derivatives by inhibiting 5‐enolpyruvyl shikimate‐3‐phosphate (EPSP) synthase. Inhibition of EPSP synthase also leads to the accumulation of high levels of shikimate, benzoic acids and benzoic acid derivatives. The sulfonylureas and p‐nitro‐substituted diphenylether (DPE) herbicides can cause increases in the level of cinnamatederived phenolic compounds and the DPEs can cause dramatic increases in terpenoid stress metabolites. Certain fungicides are thought to act through enhancing the capacity of plants to produce phytoalexins. These and other data suggest that sublethal effects of pesticides on target and non‐target plants can significantly affect agricultural ecosystems by altering the synthesis of compounds important in inter‐ and intraspecies interactions.
The effects of chlordimeform on the behaviour of Pieris brassicae larvae
Authors: Blackwell Alison
Published: November 2006

Larvae of the Large White butterfly, Pieris brassicae L., are important pests of cruciferous crops. Third and fifth instars were treated topically with sublethal doses of the formamidine pesticide chlordimeform, which induced a number of excitatory actions at doses as low as 0·2 μg g−1. Normal feeding was inhibited. Also, a locomotor‐stimulant action was observed but higher doses interfered with this action by disrupting proleg coordination. Older larvae were less susceptible to these effects. Within 5 h, excitation was substantially reduced in all larvae. The results are discussed in terms of possible sublethal contributions to crop protection.
Acute effects of amitraz on the acoustic startle response and motor activity
Authors: Crofton Kevin M. , Boncek Virginia M. , Reiter Lawrence W.
Published: November 2006

To characterize further the behavioral toxicity of amitraz, comparisons were made between the effects of amitraz on motor activity, the acoustic startle response, body temperature, and body weight in male Long‐Evans rats. Acute dosage‐effect and time‐course determinations of motor activity were made using figure‐eight mazes. Dosage‐effect and time‐course determinations for the acoustic startle response were measured using a 13 kHz, 120 dB(A), 40 ms tone as the eliciting stimulus, at each of three background white‐noise levels (45, 60 and 75 dB). Amitraz (0, 25, 50, 100 or 200 mg kg−1) was administered orally in 1.0 ml kg−1 of the vehicle (‘Emulpnor’+ ethanol + saline, 5 + 5 + 90 by volume). Amitraz produced a dosage‐ and time‐dependent decrease in motor activity which lasted from 4 to 96 h post‐administration. The effects of amitraz on the acoustic startle response consisted of an increased latency and a decreased amplitude and sensitization. The time‐course of effects on the acoustic startle response were more transient (4‐24 h) than the effects on motor activity. Amitraz‐exposed animals had decreased body weight that did not return to control levels until 120 h (five days) post‐administration. Amitraz administration produced a transient (4 h) dosage‐dependent decrease in body temperature. The highest dosage of amitraz administered, 200 mg kg−1, produced 65% mortality within 72 h; 100 mg kg−1 was the lowest dosage that produced mortality (8 %). Significant behavioral effects were seen at dosages as low as 25‐50 mg kg−1. These data provide quantitative measures of the acute effects of amitraz following oral administration on sensory/motor systems in the rat.
Aquatic organisms and pyrethroids
Authors: Hill Ian R.
Published: November 2006

Under laboratory conditions, in water without particulate matter, pyrethroid insecticides have a high toxicity to fish and some aquatic invertebrates. The pyrethroids are of very low water solubility/high lipophilicity, and therefore are rapidly and strongly adsorbed to particulate material. In the adsorbed state their bioavailability to aquatic organisms is greatly reduced. Consequently, under field conditions the aquatic impact of these insecticides is likely to be much less than might be predicted by laboratory acute or chronic toxicity test data.

Over the past 10 years a large number of aquatic field studies have been carried out with pyrethroids, in natural farm ponds, streams and lakes and also in mesocosms (experimental ponds and enclosures). Recent investigations, to meet the requirements of the United States Environmental Protection Agency, have been most extensive. These studies, done in replicated experimental ponds of at least 0‐04 ha, each require at least 20 man‐years of effort.

Following agricultural applications of the pyrethroid insecticides, spray‐drift or run‐off may cause minor effects upon some aquatic organisms. Algae, microorganisms, annelids, gastropods and fish are all unaffected, but some impact may occur upon certain zoo‐plankton and on aquatic stages of insects. However, with products for which realistic field studies have been reported, the effects are mostly transient and are unlikely to cause adverse changes in the populations or productivity of aquatic ecosystems.
Photochemistry of halogenated benzene derivatives. Part IX. environmental aquatic phototransformation of bromoxynil (3,5‐dibromo‐4‐hydroxybenzonitrile)
Authors: Kochany Jan , Choudhry Ghulum Ghaus , Webster G. R. Barrie
Published: November 2006

Photochemistry of the herbicide 3,5‐dibromo‐4‐hydroxybenzonitrile (bromoxynil) (I) was investigated by irradiating at approximately 313 nm. Aqueous phase photoreactions of 0.078–7.800 × 10−5m solutions of I were carried out at different pH values. Quantum yields for the loss of I in buffered solutions were 0.008 (±0.0004), 0.048 (±0.0024), and 0.044 (±0.0022) at pH 2.6, 7.0, and 11.0, respectively. In neutral and basic conditions, I absorbed more strongly at wavelengths > 290 nm, an environmentally significant region. Phototransformation of I was monitored by HPLC and UV‐VIS spectrometry. All photoreactions of I gave rise to the generation of two products, 3‐bromo‐4‐hydroxybenzonitrile and 4‐hydroxybenzonitrile. The former photoproduct was tentatively identified from its mass spectral data. The photoproducts can be accounted for with a proposed mechanism involving free radicals.
The effect of host plant on colorado potato beetle (coleoptera: Chrysomelidae) susceptibility to pyrethroid insecticides
Authors: Ghidiu Gerald M. , Carter Catherine , Silcox Charles A.
Published: November 2006

In laboratory studies, Colorado potato beetle (CPB) (Leptinotarsa decemlineata Say) reared on eggplant were significantly more susceptible to permethrin than CPB reared on tomato. Field studies conducted in 1984 and 1985 showed that the percentage reduction of CPB larvae reared on eggplant due to foliar applications of fenvalerate was significantly greater than the percentage reduction of CPB larvae reared on either potato or tomato. Plant defoliation was greater on eggplant and potato than on tomato. Eggplant and potato yields increased as the dose of fenvalerate increased and the potato beetle population decreased, but tomato yields were unaffected by fenvalerate treatments. The effects and biological activity of individual plant chemical compounds (i.e., glvcoalkaloids) in various Solanum species need to be examined in detail before the full significance of the role of these compounds in host‐plant resistance and their interaction with CPB insecticide resistance are understood.
Organosilane insecticides. Part I: Biological and physical effects of isosteric replacement of silicon for carbon in etofenprox and MTI‐800
Authors: Sieburth Scott McN. , Manly Charles J. , Gammon Derek W.
Published: November 2006

Substitution of silicon for carbon was explored in etofenprox and MTI‐800, primarily to establish the suitability of silicon for pesticide construction and to probe steric effects. It was shown that silicon is an effective building block for insecticides with subtle qualitative and quantitative differences relative to the carbon analogs. The silanes were slightly less toxic to insects than the carbon analogs (relative potency of 0.2‐0.6) but the silane analog of MTI‐800 was considerably less toxic to fish (0% mortality at ≥50 mg liter−1) than MTI‐800 itself (LC50 = 3 mg liter−1). The mode of action of both carbon and silicon compounds was similar in the intact, electrode‐implanted cockroach and involved repetitive firing of a sensory nerve; potency measurements were also made using an in‐vitro nerve assay. The possible metabolic and physicochemical contributions to the observed insecticide potencies were explored using synergism studies, physical chemistry measurements and quantum mechanical calculations.
Synthesis and pesticidal activities of certain fluorine‐containing 9H‐1,2,4‐triazolo[4,3‐a] benzimidazoles
Authors: Joshi Krishna C. , Jain Renuka , Dandia Anshu , Sharma Kanti , Jain Satish C.
Published: November 2006

Several fluorine‐containing 9H‐1,2,4‐triazolo[4,3‐a]benzimidazoles were synthesised using new methodology. 2‐Hydrazinobenzimidazoles on acylation with acid anhydrides afforded 2‐(acylhydrazino)benzimidazoles which, in turn, were cyclised with polyphosphoric acid to afford the title compounds. Representative compounds were screened for antibacterial, antifungal and herbicidal activities. The fluorinated derivatives showed enhanced antibacterial and antifungal activities on comparison to nonfluorinated analogues. Two of the derivatives showed 100% control of some grass weeds under pre‐emergent conditions at 10 kg ha−1.
New insecticides by replacement of carbon by other Group IV elements
Authors: Sieburth Scott McN. , Lin Sarah Y. , Cullen Thomas G.
Published: November 2006

All of the Group IV elements, C, Si, Ge, Sn and Pb, form four tetrahedrally disposed bonds and could be considered as replacements for each other. Because the atomic radius increases linearly with increasing row number, this replacement can also be considered as a probe of steric effects. The use of silicon, with its high natural abundance and non‐toxic nature, has received the most attention. Examples of silicon‐for‐carbon exchange can be found for all major classes of insecticides, including carbamates, phosphates, pyrethroids, as well as DDT and juvenile hormone analogs. Generally, the silicon analogs retain insecticidal activity. A silicon analog of MTI‐800 (dimethyl‐4‐ethoxyphenyl‐I‐(3‐(4‐fluoro‐3‐phenoxyphenyl)propyl)silane) is a broad spectrum insecticide. This silane was used as a starting point for building new silane analogs as potential insecticides. Two analogs were particularly noteworthy. A silane with a cyclopropyl group was found to be non‐toxic to Trichoplusia ni (cabbage looper) while the corresponding carbon compound was a potent insecticide. An analog containing a silicon‐hydrogen bond, a structural feature reported to be unstable in vivo, was found to be significantly insecticidal both topically and in foliar tests. The latter compound suggests that biologically active silanes can encompass broader structural types than previously anticipated.
Sensitivity of the pear scab fungus (Venturia nashicola) to three ergosterol biosynthesis‐inhibiting fungicides
Authors: Ishii Hideo , Takeda Hiromi , Nagamatsu Yoshinori , Nakashima Hideki
Published: November 2006

Sensitivity patterns of Venturia nashicola strains to ergosterol biosynthesis inhibitors (EBIs) were explored in order to obtain ‘base‐line’ data. For triflumizole or bitertanol, sensitivity was examined in mycelial growth tests and comparisons were based on EC50 rather than MIC values. It was also indicated that measurements of germ‐tube length rather than observation of conidial germination or septum formation were needed to assess sensitivity to these fungicides as a rapid and simple method. Field trials were carried out to examine how fast EBIs might select for lower sensitivity in field populations of V. nashicola. Results suggested that any shifts to lower EBI sensitivity in this fungus would not proceed very quickly. It might be possible to avoid potential problems of EBI resistance and maintain the long‐term effectiveness of EBI fungicides in orchards by applying them sparingly.
Antimicrobial activity of some N‐(fluorophenyl)maleimides
Authors: Watanabe S. , Igarashi Y. , Yagami K. , Imai R.
Published: November 2006

A variety of N‐(fluorophenyl)maleimides were prepared from the reaction of maleic anhydride and fluorophenylamines, and their antimicrobial activities examined. N‐(Monofluorophenyl)maleimides exhibited antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli, and no activity against Pseudomonas aeruginosa. These compounds also showed antifungal activity against Aspergillus niger, Penicillium citrinum, Cladosporium cladosporioides and Aureobasidium pullulans. All N‐(fluorophenyl)maleimides tested showed activity against yeasts.
Lysimeter studies
Authors: Leake Christopher R.
Published: November 2006

Traditionally, the potential mobility of agricultural xenobiotics in soil has been assessed under controlled laboratory conditions. This continues to have a role in determining relative movement, but there is an increasing need to be confident that xenobiotics will not reach the groundwater under field conditions. Outdoor lysimeters using intact soil cores provide a more realistic means of assessment than laboratory techniques without the complications and uncertainties of field studies. Two methods of collecting intact lysimeter cores are described, together with a series of experiments involving the degradation and mobility of the radiolabelled herbicide benazolin‐ethvl (ethyl 4‐chloro‐2,3‐dihydro‐2‐oxo‐1,3‐henzothiazol‐3‐ylacetate).
New heterocyclic herbicidal sulphonamides
Authors: Percival Albert
Published: November 2006

The sulphonylurea structures and their relationships with the 1,2,4‐triazolo[1,5‐a]pyrimidinesulphonamides are first discussed. Three novel examples of heterocyclic sulphonamides, pyrazolo[1,5‐a]pyrimidine‐2‐sulphonamides, thiazolo[3,2‐b][1,2,4]triazole‐2‐sulphonamides and 1,2,4‐triazole‐3‐sulphonamides are highlighted and their synthesis, biological activity and soil behaviour are described.
The toxicity of deltamethrin to pine beauty moth Panolis flammea schiff. and its parasitoids Barichneumon bilunulatus grav. and Rictichneumon pachymerus katz
Authors: Glowacka Barbara , Malinowski Henryk
Published: November 2006

The toxicity of deltamethrin to larvae of the pine beauty moth, Panolis flammea Schiff., and its two parasitoid species, Barichneumon bilunulatus Grav. and Rictichneumon pachymerus Katz., was evaluated. Two methods, exposure of insects on treated filter paper and topical application of insecticide, were used. Results showed that larvae of the pest were many times more susceptible to deltamethrin than imagines of either of the two parasitoid species.
Herbicidal activity and mode of action of vulgamycin
Authors: Babczinski Peter , Dorgerloh Michael , Löbberding Antonius , Santel Hans‐Joachim , Schmidt Robert R. , Schmitt Peter , Wünsche Christian
Published: November 2006

The antibiotic vulgamycin was isolated from a new strain of Streptomyces. Vulgamycin shows herbicidal activity when applied post‐emergence. It controls dicotyledonous weeds and grasses such as Setaria sp. at dosages between 125 and 500 g ha−1. Crops such as cotton, barley and maize tolerate vulgamycin very well. Biochemical mode‐of‐action studies indicate some effect of vulgamycin on an isoleucine‐dependent step within the cell cycle, so‐called GI‐arrest.
Comparative measurements of resistance to insecticides in three closely‐related old and new world bollworm species
Authors: Ernst Gert H. , Dittrich Volker
Published: November 2006

Toxicity measurements were made with three closely‐related Bollworm species, Heliothis virescens F., Helicoverpa zea (Boddie), and Helicoverpa armigera (Huebner) using insecticides of 3 different chemical classes. Tests were carried out by a leaf‐dip method using neonate larval stages, a topical application test on 3rd larvae, and a topical test with imagines. H. armigera populations from Ivory Coast, Turkey, Thailand, and India were obtained and investigated. H. virescens originated from the USA and Colombia, and H. zea from Guatemala and Nicaragua. Resistance was expressed in all species, the sensitive reference strains having similar LC50s in tests with monocrotophos, profenofos, thiodicarb, and methomyl. Since resistance appeared not to be a quality related to species but rather a feature common to all of the samples investigated, its origin must be connected with the type of cotton culture and the selection pressure they were subjected to in their respective agro‐ecosystem. Resistance was highest for monocrotophos and cypermethrin in Central American countries, differences in the treatment regime being reflected by the resistance levels attained. In all stages tested, resistance was sufficiently well expressed to make a monitoring system based on neonate larvae, the 3rd larval stage, or imagines of the species possible. The final decision as to which should be used for a general, comparative monitoring system, therefore, should be governed by the technical parameters of the testing process.
Development and validation of residue methods for the determination of the pyrethroids lambda‐cyhalothrin and cypermethrin in natural waters
Authors: Hadfield Stephen T. , Sadler Jill K. , Bolygo Elek , Hill Ian R.
Published: November 2006

This paper describes the development of methods suitable for the sampling and analysis of the pyrethroid insecticides lambda‐cyhalothrin and cypermethrin in natural waters. A solid‐phase water‐sampling method which avoids the requirement for transport and storage of large volumes of water is described. This method is shown to be capable of extracting trace levels (ng litre−‐1) of the title compounds from natural waters with efficiencies of at least 80%. Chromatographic analysis of processed samples by gas chromatography–electron capture detection enables determination of residues at levels of 1–2 ng litre−‐1 in water.
Inheritance of fenvalerate and carbofuran resistance in colorado beetles—Leptinotarsa decemlineata (Say)—from North Carolina
Authors: Heim D. Craig , Kennedy George G. , Gould Fred L. , Van Duyn John W.
Published: November 2006

Progeny from reciprocal F1 crosses and F1 backcrosses between fenvalerate‐resistant and fenvalerate‐susceptible Colorado beetles, Leptinotarsa decemlineata (Say), and between carbofuran‐resistant and carbofuran‐susceptible Colorado beetles were bioassayed to investigate the mode of inheritance of resistance to these chemicals. Bioassays of progeny from these crosses indicate that resistance to fenvalerate is inherited in a semi‐recessive, sex‐linked manner and carbofuran resistance is inherited in a partially dominant autosomal fashion. Log concentration/probit mortality lines and chi‐square tests, however, indicate that multiple genes may be involved in resistance to both insecticides.
In‐vitro systems for studying phytotoxicity and metabolic fate of pesticides and xenobiotics in plants
Authors: Harms Hans H.
Published: November 2006

Plant cell cultures have been used for an ecotoxicological evaluation of pesticides and xenobiotics and results are compared with those using intact plants grown under aseptic conditions. Both plant test systems were able to metabolize the compounds by common metabolic pathways. Qualitatively, the metabolites were the same in both systems. However, using cell suspension cultures, the results may be obtained more quickly with less analytical expense. Such cultures are therefore useful systems for obtaining rapid evidence of the ecotoxicological behaviour of chemicals in plants.
Effects of Sterol Biosynthesis Inhibitor Fungicides on Growth and Sterol Composition of Ustilago maydis, Botrytis cinerea and Pyrenophora teres
Authors: Loeffler R. S. Thomas , Hayes Ann L.
Published: November 2006

The effects of the sterol biosynthesis inhibitor (SBI) fungicides fenarimol, fenpropimorph, imazalil, prochloraz, propiconazole and triadimenol on growth and sterol composition of Ustilago maydis, Botrytis cinerea and Pyrenophora teres, grown from spores or sporidia in liquid culture, were determined. Growth of U. maydis was only slightly inhibited by SBI fungicides at concentrations which caused considerable changes in both sterol content and composition. Conversely, in B. cinerea and P. teres, growth was strongly inhibited under conditions where ergosterol was still the predominant sterol, suggesting that, in these two fungi, growth may be more sensitive to SBI fungicides than overall sterol production. Demethylase inhibitor fungicides behaved as a homogeneous group in their effects on growth and on sterol profiles of the three fungi studied.
Structure and general properties of mineral and vegetable oils used as spray adjuvants
Authors: Hamilton Richard J.
Published: November 2006

The abiogenic and biosynthetic origins of mineral and vegetable oils are contrasted and the importance of soybean, palm, rape seed and sunflower as the major source of fatty acids is highlighted. The cheaper oils derived from animal sources also provide fatty acids. The extraction and refining processes for vegetable oils are explained, the composition of typical vegetable oils is discussed and the importance of the glyceride structure to the physical properties of the oils is emphasised. Stability, volatility and viscosity of vegetable oils are considered.

Production of fatty acids by fat‐splitting methods and the formation of methyl esters by inter‐esterification are outlined. Mineral oil compositions are detailed and their properties explained.
Use and mode of action of adjuvants for herbicides: A review of some current work
Authors: Kirkwood Ralph C.
Published: November 2006

The use of surfactants, mineral and vegetable oils, emulsifiers and fertiliser salts, such as ammonium sulfate, can greatly enhance the activity of foliage‐applied herbicides. Adjuvant‐herbicide interactions are reviewed with particular reference to the benefits, including dose reduction, enhanced and more consistent herbicide activity, and the nature of underlying mechanisms; the use and role of surfactants receive particular attention. Surfactants are used as activators in commercial formulations of many herbicides to improve their foliar absorption and ultimate biological activity. Current views on their influence are considered in relation to surface phenomena, solubilisation of non‐polar active ingredients, wax dissolution, cuticle penetration, preferential sites of penetration, membrane permeability and possible systemicity. The importance of a number of moderating factors (plant, chemical and environmental) is discussed in the light of current work, with particular regard to herbicide polarity, surfactant type, Hydrophile‐Lipophile Balance and critical micelle concentration. Current studies on the influence of nonionic polyoxyethylene surfactants of differing ethylene oxide (EO) content have underlined the importance of EO number to their activity.
Topical and oral activities of imidacloprid and cyfluthrin against susceptible laboratory strains of Heliothis virescens and Spodoptera littoralis
Authors: Lagadic Laurent , Bernard Ludovic , Leicht Wolfgang
Published: November 2006

Activity of the newly developed nitroguanidine insecticide imidacloprid against fourth‐instar larvae of insecticide‐susceptible strains of the tobacco budworm, Heliothis virescens F., and the Egyptian cotton leafworm, Spodoptera littoralis (Boisd.) was determined from topical application and oral ingestion tests. The activity of imidacloprid was compared to that of cyfluthrin. The LD50 at 48 h of topically applied imidacloprid was estimated as 7.7 and 36.7 μg larva−1 for H. virescens and S. littoralis, respectively. In oral tests, the LC50 at 48 h of imidacloprid incorporated into artificial diet was estimated at 821.0 and 17.7 μg (g food)−1 for H. virescens and S. littoradis larvae, respectively. Imidacloprid showed lower contact and oral toxicities to both species than cyfluthrin, but the difference was much less important in ingestion tests. Mortality caused by both insecticides occurred more slowly in dietary exposures than in topical applications, but imidacloprid acted much more rapidly than cyfluthrin in ingestion tests. When incorporated into the diet, imidacloprid did not produce feeding deterrence, in contrast to cyfluthrin which exhibited a slight repulsive/antifeedant effect. Though cyfluthrin was the more active compound against both H. virescens and S. littoralis larvae, imidacloprid acted much more rapidly in ingestion bioassays. However, the level of activity of the compound is not high enough to provide efficient control of cotton insect pest populations in the field.
The dietary toxicity of deltamethrin to the carabid,Nebria brevicollis(F.)
Authors: Wiles John A. , Jepson Paul C.
Published: November 2006

Batches of adultNebria brevicollis(F.) (Coleoptera: Carabidae) were provided with freeze‐killed aphids,Metopolophium dirhodum(Walk.) (Homoptera: Aphididae), that had been treated topically with 30 ng a.i. deltamethrin. Beetles in different hunger states were found to consume contaminated aphids, but they consumed significantly fewer aphids than control beetles. The mean numbers of contaminated aphids eaten increased with hunger‐level, from 2.5 aphids per beetle for those provided with food 24 h before exposure, to 4.5 aphids per beetle for those provided with food 120 h prior to exposure. The highest mortality that occurred over the following six days after consumption of contaminated aphids was 27% for the beetles that had been fed 120 h before exposure and the lowest was 13% for the beetles that had been fed 24 and 48 h prior to exposure. A regurgitation response was observed in 53–80% of the beetles that had consumed deltamethrin‐treated aphids. The beetles that survived consumption of treated aphids showed a short‐term reduction in mean numbers of untreated aphids consumed relative to the control beetles. Dietary and topical dose‐response data for deltamethrin andN. brevicolliswere compared by probit analysis and maximum likelihood procedures. The dietary exposure probit line had a significantly steeper slope than the topical exposure probit line but the two lines occupied similar positions along the dose axis. The steepness of the dietary exposure probit line may be partly explained by the regurgitation response shown by the beetles, which causes water loss and may amplify toxic effects. The results indicated that the consumption of deltamethrin‐contaminated prey may be an important cause of predator mortality soon after pesticide application.
Mobility of fomesafen and atrazine in soil columns under saturated‐ and unsaturated‐flow conditions
Authors: Weber Jerome B. , Strek Harry J. , Sartori Jose L.
Published: November 2006

The relative mobilities of14C‐labeled fomesafen and atrazine in Norfolk sandy loam (Typic Paleudult), Drummer silt loam (Typic Haplaquoll). Cape Fear sandy loam, (Typic Umbraquult), and a Brazilian Oxisol clay (Typic Acrustox) were studied using 50 cm of water applied to 30–5‐cm soil columns under unsaturated‐ and saturated‐flow conditions. Both herbicides were more mobile in Norfolk sandy loam than in Oxisol clay, Drummer silt loam, or Cape Fear sandy loam. Herbicide mobility was inversely related to organic and humic contents of the soils. Mobility of fomesafen was highly correlated with that of atrazine in the soils. Fomesafen was generally less mobile that atrazine under unsaturated‐flow conditions and more mobile under saturated‐flow conditions. Liming a Norfolk sandy loam increased, and oven drying decreased, fomesafen mobility.
Microbial fungicides—the natural choice
Authors: Lange Lene , Breinholt Jens , Rasmussen Frank W. , Nielsen Ruby I.
Published: November 2006

Fungicidally active secondary metabolites have been found throughout the microbial system, with major new discoveries especially from Actinomycetes and Basidiomycetes. New and interesting modes of action have been revealed (e.g. the unique way in which strobilurin inhibits mitochondrial respiration, or trehalase inhibition by validamycin). These new compounds have been used either directly as microbially produced fungicides (e.g. kasugamycin against rice blast) or as lead molecules for chemical synthesis of novel chemistry (e.g. pyrrolnitrin used as a fungicidal seed dressing).

However, a real breakthrough, resulting in a major new group of fungicides based on naturally occurring metabolites is yet to come. Three new fungicidal fungal metabolites are described and one is highlighted in detail in order to illustrate the entire process from isolation of antagonistic microorganisms to structure elucidation of the active molecule.
Metabolism of EPTC by a pure bacterial culture isolated from thiocarbamate‐treated soil
Authors: Tal Abraham , Rubin Baruch
Published: November 2006

A bacterial strain has been isolated from an enhanced thiocarbamate degradation soil and identified as Corynebacterium sp. The strain was capable of rapidly metabolizing EPTC in a liquid culture where the herbicide was the sole source of carbon. Evolution of high quantities of [14C]carbon dioxide was coupled with a rapid decline of [14C]EPTC in the medium; after 12 h incubation these accounted for, respectively, 60% and 0% of the recoverable radioactivity. Radioactivity in the polar extract increased gradually up to 20% after 6 h of incubation and then declined slowly. TLC analysis and identification based on comparison to reference compounds showed that the polar extract consisted of EPTC sulfoxide and two conjugates, EPTC‐GSH and EPTC‐cysteine (1·8%, 3·4%, and 16%, respectively). Piperonyl butoxide and tetcyclasis, but not tridiphane, were found to be effective inhibitors of EPTC metabolism in the bacterial culture, suggesting that the breakdown of EPTC might be carried out by a cytochrome P‐450 monooxygenase‐type activity. The thiocarbamate extender, dietholate, also strongly inhibited the metabolism of EPTC in bacterial culture. Based on these results it was postulated that the bacteria metabolize EPTC mainly by hydroxylation of the α‐propyl carbon finally to release [14C]carbon dioxide, while EPTC sulfoxidation appears to be a minor route.
Herbicidal selectivity of (E)‐3‐(2,4‐dichlorophenoxy)acrylates: QSAR study with molecular connectivity indices
Authors: Šoškić Milan , Sabljić Aleksandar
Published: November 2006

The aim of this study was to generate a quantitative model of the herbicidal selectivity of (E)‐3‐(2,4‐dichlorophenoxy)acrylates against barnyard grass and rice. Molecular connectivity indices and other topological quantities were used as molecular descriptors. A solid and sound correlation (r = 0·91) was obtained between the selectivity index ΔpI50 (defined as logarithmic ratio of biological activities observed in the two tested plant species) and the three topological quantities: the first‐order molecular connectivity index, the valence fifth‐order path/cluster molecular connectivity index, and the presence of a cyclic alcohol moiety. Our QSAR analysis revealed that the size of a molecule accounts for a large part of the variation in the ΔI50 data. However, the degree of branching and the presence of a cyclic group in the alcohol moiety have a significant influence on the selectivity of (E)‐3‐(2,4‐dichlorophenoxy)acrylates. The derived selectivity model, when compared with the corresponding empirical model, based on the 1‐octanol/water partition coefficient and Taft's polar constant, shows a far superior performance in accuracy.
Modeling environmental effects on enhanced carbofuran degradation
Authors: Parkin Timothy B. , Shelton Daniel R.
Published: November 2006

Prediction of the fate of pesticides in soil is of interest from an environmental (pollution) as well as an agricultural (efficacy, carryover) viewpoint. Two environmental parameters that control microbial degradation of pesticides in soil are moisture and temperature. This study was designed to quantify the impact of soil water content and temperature on microbial degradation rates of the insecticide carbofuran (2, 3‐dihydro‐2, 2‐dimethylbenzofuran‐7‐yl methyl‐carbamate). Carbofuran degradation was determined by monitoring the [ 14 C] carbondioxide production from soils amended with [carbonyl‐ 14 C]carbofuran. Soils were incubated at seven soil‐water tensions over the range of 0–03 to 1–5 MPa, and at five temperatures (10°C to 30°C). The sigmoidal degradation kinetics observed from these incubations were modeled using a general saturation model. For the moisture experiments, maximum rate of hydrolysis and half‐life (DT50) were accurately modeled by an exponential relationship. The response of carbofuran degradation to temperature was also well described by an exponential relationship, from which it was estimated that the Q10 associated with the maximum rate was 1.68, and the Q10 for DT50 was 1–89.
Modelling the microbial breakdown of pesticides in soil using a parameter estimation technique
Authors: Vink Jos P. M. , Nörtersheuser Peter , Richter Otto , Diekkrüger Bernd , Groen Klaas P.
Published: November 2006

Results of field measurements and laboratory experiments were used to simulate the behaviour of 1,3‐dichloropropene (1,3‐D) in a loamy sand soil. Microbial activity was described using pre‐set conditions to compute transformation rates as dependent on compound concentrations and temperature. These kinetics could only be analysed using non‐linear transformation rates. To link the development of microbial populations and the consumption of the compound over time, an iterative technique was used to estimate the necessary parameters.
The induction and characterisation of isolates of Pseudocercosporella herpotrichoides with altered sensitivity to the fungicide prochloraz
Authors: Julian Angela M. , Hardy Josephine E. , Lucas John A.
Published: November 2006

Isolates of Pseudocercosporella herpotrichoides (Fron.) Deighton, causal agent of eyespot disease of cereals, with reduced sensitivity to the imidazole fungicide prochloraz were produced by spontaneous selection on fungicide‐amended media or by successive rounds of ultra‐violet (U V) irradiation of conidia. Resistance frequencies were similar to those obtained for other sterol‐biosynthesis‐inhibiting (SBI) compounds. Stability testing indicated that a large proportion of the UV‐induced mutants reverted rapidly to wild‐type sensitivity levels. However, the spontaneously selected strains, and strains produced after the third round of mutation proved more stable. Strains produced by spontaneous selection and from a single round of UV irradiation showed relatively low levels of resistance, in most cases within the range shown by the European field population. Subsequent rounds of UV irradiation raised resistance levels by factors of between 5 and 16 times. Growth rate in culture and sporulation ability were impaired in some, but not all. strains. Spontaneous mutants showed no decrease in pathogenicity to cereal hosts while UV‐induced strains were more variable, with some giving significantly reduced infection scores. The spontaneous mutants, and some of the UV‐induced strains, gave higher infection scores on plants treated with prochloraz than on untreated plants. This may have been due to changes in the stem base microflora resulting in reduced competition. The findings from this study suggest a multi‐factorial basis for resistance, resulting in directional rather than disruptive selection for field resistance.
Insecticidal properties of monoterpenoid derivatives to the house fly (diptera: Muscidae) and red flour beetle (coleoptera: Tenebrionidae)
Authors: Rice Pamela J. , Coats Joel R.
Published: November 2006

Monoterpenoid derivatives were synthesized and their insecticidal activities were evaluated against red flour beetles, Tribolium castaneum (Herbst), in fumigant bioassays and against house flies Musca domestica (L.) in topical, fumigant, and ovicidal bioassays. Acetate derivatives and haloacetate derivatives were compared with each other, and with the parent monoterpenoid to determine structure‐activity relationships. Acetate derivatives were more active than the propionate derivatives of cyclic monoterpenoids in the topical, fumigant, and ovicidal bioassays. Pivalates were topically more insecticidal than acetates to adult house flies, while the acetates had the greater ovicidal activity. Acetates and pivalates were more effective than haloacetates in the topical, red flour beetle fumigation and ovicidal bioassays. Fluoroacetates of cyclic monoterpenoids were the most effective house fly fumigants, followed by acetates, and trichloroacetates. Several derivatives were produced that displayed enhanced activity relative to the parent alcohols or phenols.
The transmission of geminiviruses by Bemisia tabaci
Authors: Markham Peter G. , Bedford Ian D. , Liu Sijun , Pinner Marion S.
Published: November 2006

The cosmopolitan whitefly species, Bemisia tabaci (Gennadius) and Trialeurodes taporariorum (Westwood) have always been regarded as pests to a large range of worldwide crops. Both species are capable of transmitting plant viruses, with T. vaporariorum being the vector of only a few ‘clostero’‐like viruses and B. tabaci the vector of viruses in several groups. The largest group of viruses transmitted by B. tabaci are the geminiviruses and B. tabaci is known to transmit around 60 members.

Until recently, B. tabaci had been associated with only a limited range of host plants within any one region, although its total potential host range was large. Virus transmission was confined within the plant host range of each regional population of B. tabaci. The emergence of the polyphagous ‘B’ biotype of B. tabaci with its increased host range of more than 600 plant species, has resulted in geminiviruses infecting previously unaffected crops. As the ‘B’ biotype spreads further into Europe, European field and glasshouse crops have been shown to be susceptible to whitefly‐transmitted viruses already endemic to other parts of the world.

More than 20 colonies of B. tabaci, including both ‘B’ and non‐‘B’ biotypes from disparate global locations have been compared for their ability to transmit more than 20 geminiviruses. All but two highly host‐specific colonies were capable of transmitting most geminiviruses tested. However, some viruses were transmitted more efficiently than others. The virus coat protein or capsid is essential for vector recognition and transmission. By comparing transmissible viruses at the molecular level to viruses that are no longer whitefly‐transmissible, the active epitope on the virus coat protein could be identified for designing future virus control strategies.
Studies on the effect of different cyclohexane‐1,3‐diones on de‐novo fatty acid biosynthesis in poaceae
Authors: Maier Anja , Golz Andrea , Lichtenthaler Hartmut K. , Meyer Norbert , Retzlaff Günter
Published: November 2006

Cyclohexane‐1,3‐diones such as the herbicides cycloxydim, sethoxydim, alloxydim and clethodim are known to be specific inhibitors of the plastid‐located acetyl‐CoA carboxylase (ACCase) in Poaceae, a key enzyme of de‐novo fatty acid biosynthesis in higher plants. Using several new cyclohexane‐1,3‐dione derivatives and known herbicides, the relationships between chemical structure and enzyme inhibition have been studied. The basic cyclohexane‐1,3‐dione structure was modified at three different positions. These compounds were tested for inhibition of the de novo fatty‐acid biosynthesis in test systems of etioplasts isolated from Avena sativa L. and Hordeum vulgare L. seedlings and also for inhibition of the isolated barley ACCase. The I50 values of these cyclohexane‐1,3‐diones were determined. The influence of the modification of alkyl chains (length and type of substituent) on the degree of ACCase‐inhibition is discussed. Several new compounds were found that were about two orders more active than the known herbicides cycloxydim or sethoxydim in the etioplast and ACCase test systems but not necessarily on the level of whole plants.
The impact of resistance on the use of second‐generation anticoagulants against rats on farms in Southern England
Authors: Cowan David , Dunsford Gary , Gill Erica , Jones Ainsley , Kerins Gerard , Macnicoll Alan , Quy Roger
Published: November 2006

Resistance amongst rats to second‐generation anticoagulants, notably difenacoum, has been recognised since the 1970s. Although initially considered to be of practical significance, doubts were subsequently expressed that the degree of resistance was sufficient to explain ineffective rodenticide treatments. Research published elsewhere demonstrated the overriding importance of poor poisoned bait consumption, caused by the influence of certain ecological factors on rat behaviour, in reducing the effectiveness of second‐generation anticoagulant treatments on farms in southern England. In this paper we consider, however, the subtle effects of resistance to anticoagulants on treatment outcome. The prevalence of resistance was increased amongst survivors of treatments and bait consumption by resistant survivors was higher than amongst susceptible survivors. The overall prevalence and degree of resistance to second‐generation anticoagulants does not, however, currently represent a practical problem. Nevertheless, selection favouring increased resistance remains a long‐term threat to the effectiveness of both difenacoum and bromadiolone.
Inheritance of resistance to a Bacillus thuringiensis toxin in a field population of diamondback moth (Plutella xylostella)
Authors: Martínez‐Ramírez Amparo C. , Escriche Baltasar , Real M. Dolores , Silva Francisco J. , Ferré Juan
Published: November 2006

Inheritance of resistance to the Bacillus thuringiensis Berl. CryIA(b) crystal protein was studied in Plutella xylostella L. (diamondback moth). A field population 50‐fold more resistant to CryIA(b) than a control susceptible strain was used. Dose‐mortality curves of the resistant population, the susceptible strain and the F1 from the two reciprocal crosses were compared. Resistance transmission to the F1 was dependent on the sex of the resistant progenitor. Sex ratio of the survivors to high doses of CryIA(b) in the F1 of the two reciprocal crosses did not corroborate the preliminary hypothesis of resistance being due to a recessive sex‐linked allele. Since, in a previous work, the loss of CryIA(b) binding capacity of resistant insects had been demonstrated, binding to midgut tissue sections from F1 individuals was also analysed. The presence of binding in all of the F1 preparations showed that, at least, a recessive autosomal allele was responsible for the loss of binding capacity in the resistant population.
Characterization of new photosynthesis‐inhibiting imidazolidine derivatives. 1. Interpretation of post‐emergence herbicidal performance from photosynthesis‐inhibiting activity and systemicity
Authors: Yanase Daisuke , Chiba Misako , Andoh Akihide , Gotoh Takeshi
Published: November 2006

An attempt was made to account for quantitatively measured herbicidal performance of foliage‐applied 5‐hydroxy‐3‐methyl‐2–oxo‐imidazolidine‐1‐carboxamide derivatives by their photosynthesis‐inhibiting activity and systemicity. Photosynthesis‐inhibiting activity was estimated from the increase of chlorophyll fluorescence intensity in Chlorella vulgaris Beijer cells measured by a microplate scanner, and systemicity was also evaluated by computer‐aided chlorophyll fluorescence imaging. The highest herbicidal performance was recorded for N‐cyclohexyl‐5‐hydroxy‐3‐methyl‐2‐oxo‐imidazo∼idine‐l‐carboxamide, a compound with the second strongest photosynthesis‐inhibiting activity and intermediate systemicity. Though neither photosynthesis‐inhibiting activity nor systemicity showed significant correlation with the actual herbicidal performance in simple regression analyses, a high predictability was found for a multiple regression on both parameters as two independent variables, suggesting that these two factors work cooperatively in the field performance.
Age‐related mechanisms of propanil tolerance in Jungle‐rice, Echinochloa colona
Authors: Leah Jon M. , Caseley John C. , Riches Charles R. , Valverde Bernal
Published: November 2006

Uptake and metabolism of propanil were measured in both susceptible (S) and resistant (R) biotypes of Jungle‐rice, Echinochloa colona (L.) link at different growth stages. Results showed that there was no significant difference in uptake between S and R biotypes of E. colona at any given growth stage, but that uptake was significantly reduced at older plant growth stages in all biotypes studied. Metabolism of propanil was more rapid in R biotypes than in S biotypes at all growth stages studied. Specific and total aryl acylamidase activity, responsible for the first stage of propanil metabolism, was higher in R biotypes than in S at all growth stages, but declined to about 50% of the maximum at older growth stages, confirming the importance of this enzyme in conferring resistance to this herbicide. The area of necrosis that developed around a single drop of propanil deposited on the adaxial leaf surface was used to assess the degree of propanil resistance; it was found that resistance increased at older E. colona growth stages in contrast to the rate of propanil metabolism and amidase activity. Treatment of leaves with the amidase inhibitors, carbaryl or piperophos, simultaneously with propanil, caused a decrease in resistance at growth stages where amidase activity was greatest. This treatment was less effective at older growth stages. These results show that, in E. colona, propanil metabolism is important for conferring resistance in younger plants (four‐six‐leaf stage). It is suggested that restricted uptake confers resistance in older plants.
Synthesis and herbicidal activity of isoxazoledicarboxylic acid derivatives
Authors: Münster Peter , Freund Wolfgang , Maywald Volker , Kükenhöhner Thomas , Gerber Matthias , Grossmann Klaus , Walter Helmut
Published: November 2006

Starting from bulk chemicals, novel isoxazoledicarboxylic acid esters were prepared and converted to the corresponding dicarboxylic acid mono‐amides in a few reaction steps and in high overall yields. Key intermediates for the cycloaddition step were chlorooximinoacetates or amides as nitrile oxide equivalents, prepared in one‐pot reactions from diketene or acetoacetic acid esters. Isoxazoledicarboxylic acid monoamides combined good herbicidal activity with chemical flexibility. They were characterized as inhibitors of photosynthesis. Particularly, they affected the photosynthetic electron transport in photosystem II and the rate of carbon dioxide assimilation. Applied post‐emergence, the new compounds were found to control a broad spectrum of key weeds in corn. Excellent activity was found on Abutilon theophrasti (L.) Medik., Amaranthus retroflexus L., Chenopodium album L., Ipomoea spp., Polygonum persicaria L., Solanum nigrum L. and Xanthium strumarium L. with rates between 0.2 and 0.5 kg ha−1. As a side‐effect, the compounds also showed activity against grass weeds. The compounds are excellent tank‐mix partners, e.g. for sulfonyl‐ureas, to complete the weed spectrum (Chenopodium album L., Solanum nigrum L.) and/or to reduce the risk of developing herbicide‐resistant weeds.