Behaviour of sulcotrione and mesotrione in two soils

The behaviour of sulcotrione, a recently introduced triketone herbicide, in various soil types was studied under laboratory conditions. In particular, degradation and sorption processes were examined on Ghent and Perpignan soils. Kinetics showed that the degradation of sulcotrione was influenced by biotic and/or abiotic factors. Half-lives ranged between 45 and 65 days. Among the degradation compounds identified were 1,3-cyclohexanedione (CHD) and 2-chloro-4-mesyl benzoic acid (CMBA), previously described as hydrolysis products, and, under special conditions, a derivative of phenylheptanoic acid (PHD). This new degradation product suggested that sulcotrione could follow two possible pathways in the soil, as in water. During the sorption study, a moderate retention of sulcotrione and CMBA relative to CHD and PHD, which were highly adsorbed whatever the soil type, was reported. Experiments carried out under the same conditions for sulcotrione and mesotrione, another triketone herbicide recommended in maize culture, made it possible to compare the two triketones and to conclude that they exhibited relatively similar behaviour in the soil, i.e. that their leaching potential needs to be properly addressed and risks evaluated. Copyright (c) 2007 Society of Chemical Industry.     

Exposure of Vicia faba to sulcotrione pesticide induced genotoxicity

Potential genotoxicity of sulcotrione 2-(2-chloro-4-(methylsulfonyl)benzoyl)-1,3-cyclohexanedione, a selective triketonic herbicide was evaluated on Vicia faba seedlings in hydroponic culture conditions. Sulcotrione (10⁻⁵, 10⁻⁴ and 2 × 10⁻⁴ M) treatments for 45 h, caused a dose dependent increase in micronuclei frequencies in root meristematic cells. Cytological analysis of root tips cells showed aneugenic effects of the sulcotrione on the plant root meristems. Sulcotrione induced chromosomal alterations at the lowest concentration used (10⁻⁵ M) when incubated for 42 h, indicating the potent mutagenic effect of this element. This is the first report for the genotoxicity of such a sulcotrione herbicide.     

Sulcotrione soil persistence and mobility in summer maize and winter wheat crops

Sulcotrione soil persistence in spring maize ( Zea mays L.) crops grown on a sandy loam soil was greater at pH 5·5 and 6·0 (soil half-life T _1/2≈58 days) than at pH 7·1 ( T _1/2 = 44 days). Sulcotrione was also applied as recommended on a summer maize crop at the five- to six-leaf growth stage, grown on a sandy loam soil. Sulcotrione soil half-life was 44 days, and the herbicide remained mainly in the 0- to 5-cm surface soil layer during the cropping period, in spite of the high water solubility and the heavy rains at the end of August; lower sulcotrione concentrations (10–18% of the total during the 2-month period after sulcotrione application) were detected in the 5- to 10-cm surface soil layer. The herbicide was applied pre-emergence to winter wheat ( Triticum aestivum L.) at four sites that differed in their soil texture and composition: loamy sand, sandy loam, loam and clay loam. Persistence was greater in the soils containing more organic matter. In soils having similar organic matter contents, persistence was lower in the soil containing more sand relative to loam and clay. During the winter crops, sulcotrione moved down to the 10- to 15-cm soil layer, in spite of the fact that the rains were lower in winter than in summer. Sulcotrione most generally was not detected in the 15–20 cm soil layer of the maize and winter wheat crops.     

Isolation and characterisation of a bacterial strain degrading the herbicide sulcotrione from an agricultural soil

BACKGROUND: The dissipation kinetics of the herbicide sulcotrione sprayed 4 times on a French soil was studied using a laboratory microcosm approach. An advanced cultivation‐based method was then used to isolate the bacteria responsible for biotransformation of sulcotrione. Chromatographic methods were employed as complementary tools to define its metabolic pathway. RESULTS: Soil microflora was able quickly to biotransform the herbicide (DT₅₀ ≈ 8 days). 2‐Chloro‐4‐mesylbenzoic acid, one of its main metabolites, was clearly detected. However, no accelerated biodegradation process was observed. Eight pure sulcotrione‐resistant strains were isolated, but only one (1OP) was capable of degrading this herbicide with a relatively high efficiency and to use it as a sole source of carbon and energy. In parallel, another sulcotrione‐resistant strain (1TRANS) was shown to be incapable of degrading the herbicide. Amplified ribosomal restriction analysis (ARDRA) and repetitive extragenic palendromic PCR genomic (REP‐PCR) fingerprinting of strains 1OP and 1TRANS gave indistinguishable profiles. CONCLUSION: Sequencing and aligning analysis of 16S rDNA genes of each pure strain revealed identical sequences and a close phylogenetic relationship (99% sequence identity) to Pseudomonas putida. Such physiological and genetic properties of 1OP to metabolise sulcotrione were probably governed by mobile genetic elements in the genome of the bacteria. Copyright © 2011 Society of Chemical Industry     

Phototransformation of metoxuron [3‐(3‐chloro‐4‐methoxyphenyl)‐1,1‐dimethylurea] in aqueous solution

UV irradiation of metoxuron in aerated aqueous solution at 254 nm or between 300 and 450 nm led initially to an almost specific photohydrolysis of the C–Cl bond, resulting in the formation of 3‐(3‐hydroxy‐4‐methoxyphenyl)‐1,1‐dimethylurea (MX3) and hydrogen chloride. The quantum yield was determined to be 0.020 (±0.005) in solutions irradiated at 254 nm. Five minor photoproducts were also identified, in particular the dihydroxydimethoxybiphenyl derivatives resulting from the phototransformation of MX3. Irradiation increased the toxicity of an aqueous solution of metoxuron to the marine bacterium Vibrio fischeri. © 2001 Society of Chemical Industry     

Increased toxicity of Bacillus thuringiensis Cry3Aa against Crioceris quatuordecimpunctata,Phaedon brassicae and Colaphellus bowringi by a Tenebrio molitor cadherin fragment

BACKGROUND: Biopesticides containing Cry insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) are effective against many lepidopteran pests, but there is a lack of Bt‐based pesticides for efficient control of important coleopteran pests. Based on the reported increase in Bt toxin oligomerization by a polypeptide from the Cry3Aa receptor cadherin in Tenebrio molitor (Coleoptera: Tenebrionidae), it was hypothesized that this cadherin peptide, rTmCad1p, would enhance Cry3Aa toxicity towards coleopteran larvae. To test this hypothesis, the relative toxicity of Cry3Aa, with or without rTmCad1p, against damaging chrysomelid vegetable pests of China was evaluated. RESULTS: Cry3Aa toxicity was evaluated in the spotted asparagus beetle (Crioceris quatuordecimpunctata), cabbage leaf beetle (Colaphellus bowringi) and daikon leaf beetle (Phaedon brassicae). To assess the effect of rTmCad1p on Cry3Aa toxicity, neonate larvae were fed Cry3Aa toxin alone or in combination with increasing amounts of rTmCad1p. The data demonstrated that Cry3Aa toxicity was significantly increased in all three vegetable pests, resulting in as much as a 15.3‐fold increase in larval mortality. CONCLUSION: The application of rTmCad1p to enhance Cry3Aa insecticidal activity has potential for use in increasing range and activity levels against coleopteran pests displaying low susceptibility to Bt‐based biopesticides. Copyright © 2011 Society of Chemical Industry     

磺草酮在土壤中的淋溶特性研究

基于所建立的土壤中磺草酮残留的超高效液相色谱-串联质谱分析方法,通过土壤薄层层析试验研究了磺草酮在中国3种典型土壤中的淋溶特性。结果表明:添加水平为1和10 mg/kg时,磺草酮在土壤中的添加回收率为80%~104%,相对标准偏差为1.2%~8.1%,最低检测浓度为0.1 mg/kg。磺草酮在河北潮土、湖南红土和吉林黑土中的比移值(Rf)分别为0.563、0.101和0.422,其在潮土和黑土中的移动性为中等,在红土中为不易移动;磺草酮在土壤中的淋溶特性与土壤理化性质密切相关,主要影响因素是土壤p H值及黏粒组分含量。     

Larvicidal activity of Cnidium monnieri fruit coumarins and structurally related compounds against insecticide-susceptible and insecticide-resistant Culex pipiens pallens and Aedes aegypti

BACKGROUND: An assessment was made of the toxicity of imperatorin and osthole identified in Cnidium monnieri fruit, 11 related compounds and five insecticides to larvae from insecticide‐susceptible Culex pipiens pallens (KS‐CP strain) and Aedes aegypti and wild C.p. pallens (YS‐CP colony) using a direct‐contact mortality bioassay. Results were compared with those of the conventional larvicide temephos. RESULTS: Imperatorin (LC₅₀ = 3.14 and 2.88 mg L^?1) was 1.9‐, 3.7‐ and 4.2‐fold and 2.4‐, 4.5‐ and 4.6‐fold more toxic than isopimpinellin, isoimperatorin and osthole against susceptible C. p. pallens and A. aegypti larvae respectively. Overall, all of the compounds were less toxic than temephos (0.011 and 0.019 mg L^?1). The toxicity of these compounds was virtually identical against larvae from the two Culex strains, even though YS‐CP larvae were resistant to fenthion (resistance ratio RR = 390), deltamethrin (RR = 164), cyfluthrin (RR = 14) and temephos (RR = 14). This finding indicates that the coumarins and the insecticides do not share a common mode of action. The structure–activity relationship indicates that the chemical structure and alkoxy substitution and length of the alkoxyl side chain at the C8 position are essential for imparting toxicity. CONCLUSION: The C. monnieri fruit‐derived coumarins and the related coumarins described merit further study as potential insecticides or lead molecules for the control of insecticide‐resistant mosquito populations. Copyright © 2012 Society of Chemical Industry     

Degradation and adsorption of terbuthylazine and chlorpyrifos in biobed biomixtures from composted cotton crop residues

BACKGROUND: Biobeds have been well studied in northern Europe, whereas little is known regarding their use in southern Europe. The degradation and adsorption of terbuthylazine (TA) and chlorpyrifos (CP) were studied in three different biomixtures composed of composted cotton crop residues, soil and straw in various proportions, and also in sterilised and non‐sterilised soil. RESULTS: Compost biomixtures degraded the less hydrophobic TA at a faster rate than soil, while the opposite was evident for the more hydrophobic CP. These results were attributed to the rapid abiotic hydrolysis of CP in the alkaline soil (pH 8.5) compared with the lower pH of the compost (6.6), but also to the increasing adsorption (K_d = 746 mL g^?1) and reduced bioavailability of CP in the biomixtures compared with soil (K_d = 17 mL g^?1), as verified by the adsorption studies. CONCLUSIONS: Compost had a dual but contrasting effect on degradation that depended on the chemical nature of the pesticide studied: a positive effect towards TA owing to increasing biodegradation and a negative effect towards CP owing to increasing adsorption. Overall, composted cotton crop residues could be potentially used in local biobed systems in Greece, as they promoted the degradation of hydrophilic pesticides and the adsorption of hydrophobic pesticides. Copyright © 2010 Society of Chemical Industry     

Iron(III) photo-induced degradation of isoproturon: correlation between degradation and toxicity

The degradation of isoproturon photoinduced by Fe(III) was investigated under both artificial and solar light. The monomeric species Fe(OH)2+ present under the experimental conditions ([Fe(III)] = 3 x 10(-4) M) is the main Fe(III) species responsible for the degradation of isoproturon. The process involves the attack on the pollutant by OH radicals generated by irradiation of Fe(OH)2+. The major primary photoproducts were identified; they accumulate in the solution medium before being degraded. The toxicity of the solution to marine bacterium Vibrio fisheri (Beijerinck) Lehmann & Neumann was monitored during the degradation process. It increased in the early stages of the reaction and, among the photoproducts, the N-formyl derivative appeared to be the major product responsible for the increase in toxicity.     

The potential utility of the leopard pleco (Glyptoperichthys gibbiceps) as a biological control of the ciliate protozoan Ichthyophthirius multifiliis

BACKGROUND: Infections of the ciliate protozoan Ichthyophthirius multifiliis Fouquet, 1876, can cause heavy mortalities in freshwater aquaculture systems. Following the ban of malachite green on fish for human consumption, currently available chemical therapies are only partially efficacious even when repeatedly applied. There is, therefore, an urgent necessity to identify more efficient and environmentally friendly control strategies. In the present study, the use of a substrate algae feeder leopard pleco, Glyptoperichthys gibbiceps, as a biological agent to control I. multifiliis infections on blue tilapia, Oreochromis aureus, reared in a warm‐water, experimental tank‐based system is explored. RESULTS: The free‐swimming protomont stage of I. multifiliis demonstrated selective settlement behaviour towards biofilm‐covered substrates. Following a controlled exposure, the number of I. multifiliis trophonts establishing on naive blue tilapia, O. aureus, was 4.9 ± 0.4 when reared with G. gibbiceps, significantly lower than when reared in isolation (13.3 ± 0.9; ANOVA, P < 0.001). CONCLUSION: This study demonstrates for the first time the potential of G. gibbiceps as a biological control to reduce I. multifiliis on commercially valuable fish stocks in warm‐water systems. This likely originated from the grazing activity of G. gibbiceps on the biofilm layer upon which the multiplicative stage of I. multifiliis was shown preferentially to settle. Therapeutic strategies against pathogenic protozoan species like I. multifiliis could greatly benefit from incorporating, where appropriate, a biological control targeting the external multiplicative life stages of the parasite, potentially reducing the current dependence on chemical interventions. Copyright © 2012 Society of Chemical Industry     

Assessment of the compensation point of Cirsium arvense and effects of competition,root weight and burial depth on below‐ground dry weight – leaf stage trajectories

Farmers are recommended to employ mechanical control when Cirsium arvense is most sensitive to disturbance. Earlier studies suggest that this occurs at a stage of minimum below‐ground dry weight, coinciding with three to seven or seven to ten leaves per shoot, depending on the definition of below‐ground dry weight. However, some farmers notice better effects when mechanical control is performed at earlier leaf stages. To estimate the compensation point (CP), defined as the minimum weight of the entire below‐ground structure of C. arvense and to further understand links between initial root weight, planting depth and crop competition, three outdoor pot experiments were performed in Sweden in 2013‐2014. We hypothesised that (i) CP likely occurs before C. arvense has developed three leaves, (ii) relative depletion of the below‐ground system at CP is less at lower initial root weight compared with higher weight, and (iii) methodological variations in CP estimations have minor impact on the results. We found that the CP for C. arvense in all treatments occurred before shoots had developed three leaves and that treatment effects were minor (<0.5 leaf stages). Leaf and leaf stage definitions, choice of leaf range and model also had minor effects on CP estimates. Depletion of planted root fragments ceased around leaf stages 3‐4, and their partial replenishment also constitutes evidence for a CP at early leaf stages. For agronomy, our results imply that mechanical control of C. arvense should be performed earlier than previously recommended, probably before reaching an average of three to four leaves per shoot.     

First outbreaks of fireblight in Slovenia1

Slovenia was recognized as free from Erwinia amylovora until 2001. A low incidence of the disease was reported in 2001 and 2002 in the north‐west uplands of the Gorenjska region. In 2001, only 3 trees in extensive orchards were found positive at one location out of 791 monitoring locations all over the country. In 2002, the same location in Naklo and a second one in a 1‐km radius were found positive, whilst 875 other monitoring locations were fireblight‐free. Despite strict phytosanitary measures implemented after discovery of the first focus, the bacterium spread in 2003 to the entire Gorenjska region, with further spread towards eastern and southern Slovenia. The NPPO registered 184 new foci by the end of the season in Gorenjska. Twenty‐three foci are scattered in other regions. Phytosanitary measures were applied in every focus. Spread of the bacterium was probably enabled by favourable weather conditions, the presence of the inoculum and intensive bee‐hive movement, resulting in flower infections. Since eradication has not been successful, it is concluded that E. amylovora is now present at low prevalence in Slovenia.     

Induction effects of host plants on insecticide susceptibility and detoxification enzymes of Bemisia tabaci (Hemiptera: Aleyrodidae)

BACKGROUND: The polyphagous B‐biotype Bemisia tabaci (Gennadius) has developed a high resistance to commonly used insecticides in China. To illustrate the induced changes by host plant, bioassay and biochemical research on five different host populations were investigated. RESULTS: Except for bifenthrin, all tested insecticides showed lower toxicity to the B. tabaci poinsettia population compared with other host populations. Moreover, four insecticides, the exceptions being abamectin and fipronil, showed highest toxicity towards the tomato population. The LC₅₀ values of the poinsettia population, particularly towards acetamiprid, were 14.8‐, 10.3‐ and 7.29‐fold higher than those of tomato, cucumber and cabbage respectively. The CarE activities of B. tabaci cabbage and cucumber populations were all significantly higher than those of poinsettia, cotton and tomato populations. The ratio of the cabbage population was 1.97‐, 1.79‐ and 1.30‐fold higher than that of poinsettia, cotton and tomato respectively. The frequency profiles for this activity also have obvious differences. The GST and P450 activities of the cucumber population were the lowest in the five host populations. CONCLUSION: Long‐term induction of host plants for B‐biotype B. tabaci could influence their susceptibilities to several insecticides. Rational selection and usage of insecticides for particular hosts will be helpful for resistance management and control of this species. Copyright © 2010 Society of Chemical Industry     

Fumigant toxicity of volatile natural products from Korean spices and medicinal plants towards the rice weevil,Sitophilus oryzae (L)

The fumigant toxicity of various volatile constituents of essential oils extracted from sixteen Korean spices and medicinal plants towards the rice weevil, Sitophilus oryzae L (Coleoptera: Curculionidae), was determined. The most potent toxicity was found in the essential oil from Mentha arvensis L var piperascens (LC₅₀ = 45.5 µl litre^?1 air). GC–MS analysis of essential oil from M arvensis showed it to be rich in menthol (63.2%), menthone (13.1%) and limonene (1.5%), followed in abundance by β‐pinene (0.7%), α‐pinene (0.6%) and linalool (0.2%). Treatment of S oryzae with each of these terpenes showed menthone to be most active (LC₅₀ = 12.7 µl litre^?1 air) followed by linalool (LC₅₀ = 39.2 µl litre^?1 air) and α‐pinene (LC₅₀ = 54.9 µl litre^?1 air). Studies on inhibition of acetylcholinesterase activity of S oryzae showed menthone to have a nine‐fold lower inhibitory effect than menthol, despite menthone being 8.1‐fold more toxic than menthol to the rice weevil. Different modes of toxicity of these monoterpenes towards S oryzae are discussed. © 2001 Society of Chemical Industry     

Effects of sulcotrione [2-(2-chloro-4-mesylbenzoyl)-cyclohexane-1,3-dione] on enzymes involved in tyrosine catabolism and the extent of the resulting tyrosinemia and its relationship with corneal lesions in rats

We aimed to investigate the effects of subchronic exposure to sulcotrione on the enzymes involved in tyrosine catabolism and the extent of the resulting tyrosinemia and corneal lesions in rats. Daily oral administration of sulcotrione at 0.1, 0.5, 5, 50 and 100 mg/kg/day markedly inhibited hepatic 4-hydroxyphenylpyruvate dioxygenase (HPPD). In response to the tyrosinemia, the activity of hepatic tyrosine aminotransferase (TAT) at each dose level was insignificantly induced and hepatic homogentisic acid oxidase (HGO) at 5, 50 and 100 mg/kg/day was markedly reduced. Repeated oral administration of sulcotrione to rats at doses of 5, 50, and 100 mg/kg/day for 90 days produced corneal lesions with an incidence of 18.8%, 75.0% and 56.3%, respectively. The significant increase in tyrosine levels indicates that the occurrence of corneal lesions in rats exposed to sulcotrione was not only associated with the concentration of tyrosine in the ocular fluid, but also with other, unidentified factors.     

Influence of caffeine on the survival of leaf-cutting ants Atta sexdens rubropilosa and in vitro growth of their mutualistic fungus

BACKGROUND: Leaf‐cutting ants collect plant fresh material for the cultivation of their mutualistic fungus. Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) cause great economic losses through their foraging activity, mainly in agriculture. The main control method is the application of granulated toxic baits incorporated with an active ingredient (AI). The present goal is to evaluate the effect of caffeine on in vitro growth of the mutualistic fungus and on the survival of the leaf‐cutting ants, aiming to verify the potential toxicity of this secondary metabolite over these organisms. RESULTS: Three distinct patterns of fungal growth correlated with caffeine concentration were observed: (1) no effect (0.01% caffeine); (2) intermediate growth reduction (0.05% caffeine); (3) drastic growth reduction (0.10 and 0.50% caffeine). The highest caffeine concentration causes fungus death in the first week. As for insect survival, caffeine does not seem to exert any effect. The treatments with diet containing caffeine showed similar values of M50, irrespective of caffeine concentration. CONCLUSION: As caffeine was shown to reduce growth of the mutualistic fungus of Atta sexdens rubropilosa, but with no conclusive effect on insect survival, a hypothetical explanation for the selection of different Coffea species by this leaf‐cutting ant species might be associated with caffeine toxicity to the fungus. Copyright © 2011 Society of Chemical Industry     

Efficacy of Bacillus thuringiensis Cry3Aa protoxin and protease inhibitors against coleopteran storage pests

BACKGROUND: Environmental impacts and resistance to insecticides pose serious challenges to stored‐product insect and other types of pest control. Insect‐resistant transgenic grain is a potential alternative to fumigants, but candidate control proteins are needed, especially for coleopterans. Therefore, we evaluated the efficacy of a coleopteran‐active toxin, Bacillus thuringiensis Cry3Aa, with or without protease inhibitors, in laboratory feeding assays against coleopteran storage pests. RESULTS: In a comparison of the toxicity of Cry3Aa protoxin towards three species of coleopteran storage pests, Tenebrio molitor L. was found to be most sensitive, Tribolium castaneum (Herbst.) was most refractory and Rhyzopertha dominica F. displayed an intermediate response. For R. dominica, Cry3Aa combined with 3500 mg potato carboxypeptidase inhibitor or 5000 mg aprotinin kg^?1 diet resulted in both delayed development and increased mortality. Potato carboxypeptidase inhibitor and bovine aprotinin reduced the LC₅₀ of Cry3Aa for R. dominica two‐ and threefold respectively. Cry3Aa treatment resulted in fewer progeny from R. dominica, and progeny was further reduced when the protoxin was combined with potato carboxypeptidase inhibitor. CONCLUSIONS: These data support the hypothesis that a combination of Cry3Aa protoxin and protease inhibitors, particularly a potato carboxypeptidase inhibitor, may have applications in control strategies for preventing damage to stored products and grains by coleopteran pests. Published 2011 by John Wiley & Sons, Ltd.     

溴氟菊酯对环境生物的安全评价研究

按照“化学农药环境安全评价试验准则”的规定, 测定了溴氟菊酯对7 种环境生物的毒性。结果表明: 其对鸟类、蜜蜂和蚯蚓的毒性较低; 对鱼类属中等毒性; 对蚤类、藻类和家蚕属高毒性。由于溴氟菊酯用量少, 在环境中降解快, 因此在田间使用时对水生生物的实际危害要小得多, 但要严格防止对邻近桑树的污染。