Suppressive activity of some glucosinolate enzyme degradation products on Pythium irregulare and Rhizoctonia solani in sterile soil

Glucosinolate degradation products (GLDPs), mainly isothiocyanates, obtained by myrosinase‐catalysed hydrolysis of glucosinolates (GLs), are an important group of natural bioactive substances. The fungitoxic activity of four GLDPs, chosen on the basis of their side‐chain structures, was assayed against Pythium irregulare and Rhizoctonia solani. The effectiveness of the degradation products (DPs) of sinigrin (alkenyl GL), epi‐progoitrin (hydroxy‐alkenyl GL), glucoiberin and glucoerucin (thiofunctionalised GLs) in inhibiting P irregulare oospore germination and R solani soil colonisation were tested in a closed system, using an artificially infected soil. The fungitoxic activity of these GLDPs varied according to their side‐chain structure. As in previous in vitro studies, the thiofunctionalised GLDPs were found the most effective, producing complete inhibition of P irregulare oospore germination (0.01 µmole g⁻¹ soil) and R solani soil colonisation (0.5 µmole g⁻¹ soil), but even sinigrin DP showed a fungitoxic activity higher than that of epi‐progoitrin DP. © 2000 Society of Chemical Industry     

Naturally occurring cyanohydrins,analogues and derivatives as potential insecticides

Several naturally occurring cyanohydrins were tested for fumigation toxicity to two insect species, the house fly (Musca domestica L) and the lesser grain borer (Rhyzopertha dominica (F)). Synthetic analogues of these compounds were tested as well. Most of the cyanohydrins tested were more toxic as fumigants to M domestica and R dominica than chloropicrin; some compounds were nearly as toxic as dichlorvos. Naturally occurring cyanohydrins were among the most toxic tested. © 2000 Society of Chemical Industry     

Multiple Resistance in the Larger House Fly Musca domestica in Germany

Populations of the housefly Musca domestica isolated from farms in different German districts with strong resistance problems were compared to laboratory strains with varying resistance spectra. Resistance against pyrethroids, organophosphates and carbamates was tested using impregnated filter papers, and by topical application using a susceptible housefly strain (origin WHO) for comparison. The multi-resistant fly strains tested had a strong resistance against these insecticide groups, ranging from 37- to >10000-fold for organophosphates and 150- to >6600-fold for pyrethroids. The constituent enantiomer pairs of the α-cyano-pyrethroid cyfluthrin were tested, as was beta-cyfluthrin. With respect to multi-resistant fly strains, the isomers II and IV had the best activity, with LD₅₀ values of 0·012 and 0·014 μg per fly, respectively. In addition, different groups of insect growth regulators (juvenile hormone analogues, chitin synthesis inhibitors and one triazine derivative) were tested in a special larvicidal test. The chitin synthesis inhibitors were quite effective against multi-resistant M. domestica strains except for one strain with strong resistance against chitin synthesis inhibitors, developed after extensive treatments with benzoylphenylureas for several years. The fly strains tested were not resistant against cyromazine. Additionally, the insecticides were combined with the synergists piperonyl butoxide, tributylphosphorotrithioate (DEF) and Cibacron blue and tested against the fly strain with the strongest resistance spectrum (‘Grimm’) in comparison to the susceptible strain (‘WHO-N’). Piperonyl butoxide had the greatest effect on the efficacy of cyfluthrin followed by Cibacron blue and DEF. In a parallel investigation with susceptible and resistant house fly strains, different enzyme activities related with resistance mechanisms were tested, e.g. glutathione S-transferase (3·5-fold) and mixed-function oxidase (2·3-fold). Implications of these results for management of insecticide resistance in M. domestica are discussed.     

Combinations of pirimiphos-methyl and carbaryl for stored grain protection

In laboratory experiments, whole wheat was treated with pirimiphos-methyl or carbaryl or combinations of these two insecticides; the treated grain was then adjusted to a 12% moisture content and stored at 25°C for bioassay at various intervals over a period of 39 weeks. Pirimiphos-methyl at 5.1 mg kg^?1 effectively controlled Sitophilus granarius (L.) and Tribolium confusum Jacquelin du Val but was ineffective against Rhyzopertha dominica (F.) CRD 118, a strain showing malathion resistance. Conversely, carbaryl at 6.5 mg kg^?1 (but not at 3.1 mg kg^?1) was effective against R. dominica, but ineffective against the other two species. A combination of pirimiphosmethyl + carbaryl, at 1.8 + 5.1 mg kg^?1, controlled S. granarius and R dominica but not T. confusum, whilst a 4.2 + 3.4 mg kg^?1 combination was relatively more effective against T. confusum but less so against R. dominica. In a separate experiment, whole wheat was treated with carbaryl at 2.5, 5.0 and 7.5 mg kg^?1 (nominal rates). Samples were stored and, at various times after the treatments, were bioassayed with R. dominica CRD 2, at 20, 25, 30 and 35°C. The results were comparable with those for the CRD 118 strain, but efficacy was reduced at higher temperatures. The combination of pirimiphos-methyl at 4–5 mg kg^?1 and carbaryl at 5–6 mg kg^?1 is suggested as a potentially useful grain protectant where R. dominica is a problem and long term storage is required. These results are discussed in relation to the protection of stored grain in Australia.     

The insecticidal and anticholinesterase activities of O,O-diethyl O-4-(2,2-disubstituted vinyl)phenyl phosphates and phosphorothioates

A series of O,O-diethyl O-4-(2,2-disubstituted-vinyl)phenyl phosphorothioates and phosphates was synthesised and examined for anticholinesterase activity to housefly and bovine erythrocyte ChE, and also for their toxicity to Musca domestica and Triatoma infestans. The synthesised phosphates were potent anticholinesterases and stronger inhibitors of housefly acetylcholinesterase than bovine erythrocyte acetyl-cholinesterase. Satisfactory correlation was obtained between the anticholinesterase activity and the Hammett σ^? constants against both enzymes, but it was not significantly improved by introducing a term for the Hansch π constant. The phosphorothioates showed poor and variable toxicity to M. domestica. On T. infestans, the only compound that showed some toxicity was the di(acetyl)-substituted product [O-4-(2-acetyl-3-oxobut-1-enyl)phenyl O,O-diethyl phosphorothioate]. For comparative studies, some commercial products were also assayed on T. infestans.     

Quantitative structure-activity relationships of pyrethroid insecticides

The structure-activity relationships of two congeneric series of pyrethroid insecticides, the methylbenzyl (1RS)-cis,trans-chrysanthemates tested against Musca domestica (houseflies) and Phaedon cochleariae (mustard beetles), and the (E)-4-aryl-3-chlorobut-2-enyl chrysanthemates and their corresponding 2,2,3,3-tetramethylcyclo-propanecarboxylates tested against M. domestica only, have been examined using multiple regression analyses and substituent constants. With M. domestica, different optimum partition values (π) were indicated for knockdown and toxicity; with P. cochleariae, an optimum π value for toxicity, similar to that for M. domestica, was obtained 24 h after application, but at later times the more lipophilic compounds were more effective. For the methylbenzyl chrysanthemates, a steric constraint associated with 3,5-dimethyl substitution reduced toxicity approximately five-fold. The influence on toxicity of geometrical isomerism and electronic effects are briefly discussed. Differences between the required polarities for knockdown and toxicity are attributed to variations in the binding affinities of pyrethroid molecules at the sites of action.     

Miticidal pyrethroids having an isobutyranilidoxime ether skeleton

Isobutyranilidoxime meta-phenoxybenzyl ethers and related compounds were synthesized. Their insecticidal activities measured against Periplaneta americana by injection were lower than that of phenothrin by factors of at least 1/60. However, some compounds were comparable to or only slightly less potent than phenothrin and tetramethrin in miticidal activity tested by a contact method against Dermatophagoides farinae, D. pteronyssinus and Tyrophagus putrescentiae. © 1998 SCI     

黄冈仓花蝽对几种仓虫的模拟控制研究

在实验室条件下,研究了黄冈仓花蝽(Xylocoris Sp.)对几种主要仓虫的控制效果。结果表明,黄冈仓花蝽对于锯谷盗、长角谷盗、姬粉盗及谷蠹成虫与卵的控制效果均在90％以上,而对于蛀入粮粒内部的谷蠹幼虫无控制效果,对玉米象控制效果较差。     

Evaluation of natural diatomaceous earth deposits from south‐eastern Europe for stored‐grain protection: the effect of particle size

BACKGROUND: The use of diatomaceous earths (DEs) provides a promising alternative to the use of contact insecticides in stored‐product IPM. Geographical origin and the physical properties of a given DE may affect its insecticidal activity. In the present study, DE samples were collected from different locations of south‐eastern Europe, and their efficacy was evaluated in the laboratory against Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujiidae), Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). In addition, three fractions comprising particles of different size were obtained from each DE sample and assessed with regards to their effectiveness against the above stored‐product insect pests. RESULTS: DE from the Greek region of Elassona was the most effective against C. ferrugineus and S. oryzae, whereas the DE Kolubara 518, mined in the Serbian region of Kolubara, was the most effective against R. dominica. Smaller particles were more effective than larger particles against the three tested species, although significant differences in the efficacy of fractions containing particles of 0–150 µm and particles with sizes of < 45 µm were not always recorded. CONCLUSIONS: Deposits from south‐eastern Europe appeared to be very effective against the tested species, and therefore this region should be further evaluated as a source of development of commercial products. Particle size is a physical property that should always be taken into account during the DE manufacturing process, as it can strongly influence the insecticidal action of a given product. Copyright © 2009 Society of Chemical Industry     

Antimycotic Screening of 58 Malaysian Plants against Plant Pathogens

Ethanolic extracts of 58 Malaysian plants belonging to 24 different families were screened for antifungal activity against seven plant pathogens using the filter paper disc diffusion technique. Two varieties of Piper betle, showed strong activity against all the pathogens tested (Colletotrichum capsici, Fusarium pallidoroseum, Botryodiplodia theobromae, Alternaria alternata, Penicillium citrinum, Phomopsis caricae-papayae and Aspergillus niger), with inhibition diameters significantly (P<0·01) bigger than 2·5 mg ml⁻¹ prochloraz or 10 mg ml⁻¹ clotrimazole. The minimum inhibitory concentrations of the ethanolic extracts of P. betle against these plant pathogens ranged between 0·01 mg ml⁻¹ and 1 mg ml⁻¹. Thirty-four other plants (Kucing gala, Limau batik, Bertholletia excelsa, Bixa orellana, Caesalpinia pulcherrima, Cerbera odollam (fruits and leaves), Colocasia gigantea, Curcuma domestica, Curcuma manga, Derris eliptica, Elephantopus scaber, Eleusine indica, Eugenia polyantha, Euphorbia hirta, Euphorbia tirucalli, Gardenia florida, Hedyotis auricularia, Hibiscus rosa-sinensis, Juniperus chinensis (three varieties), Lawsonia inermis, Lecythis ollaria, Mentha arvensis, Mimusops elengi, Ocimum sanctum, Phyllanthus niruri, Piper nigrum, Piperomia pellucida, Pedilanthus tithymaloides, Polygonum minus, Spondias dulcis, Solanum nigrum, Tinospora tuberculata) showed selective antifungal activity, while 21 species were inactive.     

Binding activity of substituted benzyl derivatives of chloronicotinyl insecticides to housefly‐head membranes,and its relationship to insecticidal activity against the housefly Musca domestica

Variously substituted benzyl derivatives of chloronicotinyl insecticides were synthesized with a wide range of substituents including halogens, NO₂, CN, CF₃ and small alkyl and alkoxy groups at the ortho, meta and para positions, as well as multiple‐substituted benzyl analogues. Their binding activity to the α‐bungarotoxin binding site in housefly (Musca domestica) head membrane preparations was measured. Among the compounds tested, the activity of the meta‐CN derivative was the highest, being 20–100 times higher than those of imidacloprid, acetamiprid and nitenpyram. The synergized insecticidal activity against houseflies was also measured for selected compounds with the metabolic inhibitor, NIA16388 (propargyl propyl phenylphosphonate). For the nitromethylene analogues, including both benzyl and pyridylmethyl analogues, higher binding activity usually resulted in higher insecticidal activity. © 2000 Society of Chemical Industry     

Insecticidal efficacy of fipronil against four stored‐product insect pests: influence of commodity,dose, exposure interval,relative humidity and temperature

BACKROUND: Fipronil is an insecticidal pyrazole that is commonly used as an insecticide in field crops, urban pesticide and veterinary medicine, but there are no reports of its evaluation against stored‐product insects. Three series of laboratory bioassays were conducted to assess fipronil as a potential grain protectant against adults of Sitophilus oryzae (L.), Tribolium confusum Jacquelin du Val, Rhyzopertha dominica (F.) and Prostephanus truncatus (Horn). Factors such as dose (0.01, 0.1, 1 and 10 mg fipronil kg^?1 grain), exposure interval (24 h, 48 h, 7 days and 14 days), temperature (20, 25 and 30 °C), relative humidity (RH; 55 and 65%) and commodity (wheat, maize, barley and paddy rice) were evaluated with regard to their impact on the insecticidal activity of fipronil. Progeny production was assessed after 64 days of exposure. RESULTS: At doses of < 1 mg fipronil kg^?1 grain, efficacy of fipronil was enhanced by an increase in temperature from 20 to 25 °C against S. oryzae or R. dominica for exposures of > 48 h and against T. confusum or P. truncatus for exposures of > 24 h. A further increase in temperature from 25 to 30 °C, although it enhanced efficacy at doses of < 1 mg fipronil kg^?1 grain against S. oryzae at all exposure intervals and against T. confusum after 7 days of exposure, it was negatively associated with efficacy against R. dominica or P. truncatus for exposures of > 24 h. By contrast, increase in RH did not have a significant impact on efficacy of fipronil. Although the performance of fipronil among the tested commodities was species dependent, this substance appeared to be less effective in paddy rice than in barley, maize and wheat. Regardless of the treated commodity, progeny production of all the tested species was almost suppressed with doses higher than 0.1 mg fipronil kg^?1 grain. CONCLUSIONS: Fipronil appeared to be a very effective alternative to the existing substances in stored‐grain protection at doses equal to or higher than 1 mg fipronil kg^?1 grain, and thus these doses require further evaluation in terms of safety for the consumer and residues on stored products. Copyright © 2010 Society of Chemical Industry     

Quantitative structure-activity study of insecticidal 2-methoxy-5-(substituted-phenyl)-1, 3, 2-oxazaphospholidine 2-sulfides against Musca domestica L. by topical application

The quantitative relationship between the structure of 2-methoxy-5-(substituted-phenyl)-1, 3, 2-oxazaphospholidine 2-sulfides (5-PMOS) and their insecticidal activity against the house fly. Musca domestica L., was analyzed using reported physicochemical parameters and regression analysis. The electronic nature of the substituent on the phenyl group of 5-PMOS has the most significant effect on the activity, followed by hydrophobic and steric effects; the optimum value of Σρ is zero and the more hydrophobic the substituents on the phenyl group, the higher the insecticidal activity. The plots of observed pLD₅₀, values against calculated pLD₅₀ values for compounds having substituents in the ortho-position deviated downwards from those of compounds having substituents at the meta and/or para positions. This ortho-effect, which reduces the insecticidal activity of compounds having substituents at the ortho-position, was expressed by a dummy parameter D, which has the value 2 for di-ortho-substituted derivatives, 1 for mono-ortho-substituted derivatives and zero for others. Thus, the highest activity was obtained for 2-methoxy-5-phenyl-1, 3, 2-oxazaphospholidine 2-sulfide, and the activity was decreased by the introduction of any substituents on the phenyl group.     

The potential use of allicin as a biopesticide for the control of the house fly,Musca domestica L.

The house fly, Musca domestica L., is a widespread pest of intensively reared livestock, where its presence negatively affects growth and productivity through the irritation their activity causes. Furthermore, adult flies mechanically vector a wide range of animal and human pathogens and, as such, pose a health risk to both livestock and people. The development of resistance in M. domestica populations to most of the insecticides used against them, coupled with diminishing product availability in many regions, means that new fly control methods and materials are constantly required. In the present study, a formulation of allicin, a compound derived from garlic cloves, was evaluated against the eggs, larvae and adults of Musca domestica L.. An in-diet LD₅₀ of 134 ppm against larvae was achieved, whilst marked ovicidal activity was also recorded. Adults were similarly affected when exposed directly and indirectly to surface residues of the compound. The results indicate that allicin exhibits potential to be used against filth flies through incorporation into their developmental substrates and, potentially, for the control of other economically important dipteran pests.     

Biological and molecular variation of Cherry leaf roll virus isolates from Malus domestica,Ribes rubrum,Rubus idaeus,Rumex obtusifolius and Vaccinium darrowii

Cherry leaf roll virus (CLRV) isolates from Malus domestica, Ribes rubrum, Rubus idaeus, Rumex obtusifolius and Vaccinium darrowii were characterized based on nucleotide sequences of a 371 bp fragment of the 3′ untranslated region (UTR) of their genomic RNAs, symptoms in the herbaceous hosts, Chenopodium amaranticolor, Chenopodium quinoa, Nicotiana benthamiana, Nicotiana occidentalis and Nicotiana tabacum, and seed transmission in N. occidentalis. The different isolates induced a range of localized and systemic disease symptoms, of varying severity, in the herbaceous hosts. The isolates from M. domestica, R. rubrum, R. obtusifolius and V. darrowii all showed greater than 80% seed transmission in N. occidentalis, but no seed transmission was observed for the R. idaeus isolate. Based on symptoms and seed transmission, the isolates appear to be biologically distinct strains of CLRV. Phylogenetic analysis of the nucleotide sequences from the 3′ UTR, commonly used to detect CLRV, showed that four isolates from M. domestica, R. rubrum, R. idaeus and V. darrowii were almost identical but an isolate from R. obtusifolius exhibited a pairwise nucleotide difference of up to 5·4% when compared to these isolates. There was no obvious correlation between sequence differences and symptomatology.     

Antimicrobial activity of some N-(fluorophenyl)maleimides

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.     

Synthesis and Structure–Activity Relationships for the Fungicidal Activity of O,O-bisaryl sec-butylphosphonates

Sixteen O,O-bisaryl sec-butylphosphonates have been synthesised by condensing sec-butylphosphonyl dichloride with substituted phenols. The compounds were tested against two phytopathogenic fungi, Rhizoctonia bataticola and Helminthosporium oryzae. The most active compound against R. bataticola is O,O-bis(3-methylphenyl) sec-butylphosphonate (ED₅₀ 29·56 mg litre^-1) and against H. oryzae, O,O-bis(2-chlorophenyl) sec-butylphosphonate and its para-chloro analogue (ED₅₀ 0·14 and 0·13 mg litre^-1 respectively). Quantitative structure–activity relationships on the fungicidal activity have been analysed by means of multiple regression analysis using physicochemical substituent parameters. Electronic parameters viz., σ and F have expressed significant variability in fungitoxicity against both the fungi, viz. R. bataticola and H. oryzae. Hydrophobic and steric parameters are also found to be important in the correlation studies. © 1997 SCI.     

Development of nanoalumina dust as insecticide against Sitophilus oryzae and Rhyzopertha dominica

This study aims to characterize and improve the insecticidal activity of nanostructured alumina dusts. To accomplish these goals, multiple solution based synthesis routes utilizing standard aluminum salt precursors were utilized to synthesize three unique types of alumina dust. These were compared with regards to morphology, particle size and surface area using electron microscopy and dynamic light scattering particle size analysis. Insect toxicity of the various dusts was assessed using two insect species that are pests of stored grain, Sitophilus oryzae and Rhyzopertha dominica. The dust synthesized using a modified glycine-nitrate combustion process consistently yielded greater mortality rates, and all dust types were more effective on S. oryzae than on R. dominica, although the difference varied across dust types. The data show that insecticidal activity is dependent on particle size, particle morphology and surface area but also indicated that minimizing particle size and maximizing surface area are not the sole dominant factors influencing efficacy. This study does however suggest that pesticide dusts can be engineered through modified synthesis to better target different insect species.     

Synthesis and insecticidal activities of unsymmetrical bis-arylalkyl ketones. A new structural concept in pyrethroids

Seventeen unsymmetrical bis-arylalkyl ketones were synthesised and their insecticidal activities against Musca domestica, Locusta migratoria, Drosophila melanogaster, Dysdercus cingulatus, Aedes aegypti and Tetranychus urticae were tested. The synergistic effect of piperonyl butoxide on the activities of some of the new ketopyrethroids against Musca domestica was also determined. Several structural variations, including substituent exchange in the aryl moieties, the position of the ketone function and increase or decrease of the length of the carbon chain connecting the two aryl moieties, were made in order to examine the structure-activity relationship. All biological activities were compared with the activity of the ether pyrethroid 2-(4-ethoxyphenyl)-2-methylpropyl 3-phenoxybenzyl ether (MTI-500).     

Novel acetylcholinesterase inhibitors: Synthesis and structure–activity relationships of phthalimide alkyloxyphenyl N,N-dimethylcarbamate derivatives

Based on the multiple binding sites of acetylcholinesterase (AChE), a series of AChE inhibitors: phthalimide alkyloxyphenyl N,N-dimethylcarbamate were designed and synthesized. AChE inhibitory activity and structure–activity relationship of the compounds were researched also. The influence of structural variations on the inhibitory potency was carefully investigated by modifying different alkyloxy chain length and position between phthalimide and phenyl N,N-dimethylcarbamate (PDM). The biological properties of the series were investigated by considering the activity on isolated enzyme. Some of the newly synthesized derivatives, when tested on isolated AChE from head of housefly (Musca domestica), were more active than PDM. The compounds J1, J2 and K1–K8 demonstrated higher inhibitory activity (5- to 404-fold) for AChE than that of PDM. In particular, compound K1 displayed the best AChE inhibition (404-fold higher than PDM), which suggested that phthalimide group of K1 strongly bound at the residues lining the gorge while phenyl N,N-dimethylcarbamate bound at the catalytic site.