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Chemical Control (chemical + control)
Selected AbstractsChemical Control of Electronic Structure and Superconductivity in Layered Borides and Borocarbides: Understanding the Absence of Superconductivity in LixBC.CHEMINFORM, Issue 45 2006Andrew M. Fogg Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Chemical control; Insecticides and resistanceENTOMOLOGICAL RESEARCH, Issue 2007Article first published online: 7 AUG 200 First page of article [source] Sugar-beet powdery mildew (Erysiphe betae)MOLECULAR PLANT PATHOLOGY, Issue 3 2002Sally Francis Summary Erysiphe betae causes sugar-beet powdery mildew, a serious fungal foliar disease resulting in sugar yield losses of up to 30%. The fungus occurs world-wide in all regions where sugar beet is grown and it also infects other edible beet crops, e.g. beetroots (garden beets). Unlike other powdery mildews, E. betae has so far received relatively little attention from pathologists and the precise mechanisms by which it infects its host remain unclear. Sources of genetic resistance have been identified in cultivated and wild Beta germplasm and molecular markers developed linked to Pm, the only single major R gene described so far, and also to QTL. Taxonomy:,Erysiphe betae (Vañha) Weltz.,Kingdom Fungi, Subdivision Ascomycotina, Class Pyrenomycetes, Order Erysiphales, Family Erysiphaceae, Genus Erysiphe. Identification:, Superficial persistent mycelium; unbranched erect conidiophores; conidia ripen singly, are hyaline, ovoid, 30,50 µm × 15,20 µm; cleistothecia globose, dark brown/black, 80,120 µm in diameter; mostly 4,8 asci per cleistothecium, mostly 2 or 3 spores per ascus. Host range:, A monophagous parasite specific to Beta species. Disease symptoms:, Infected foliage and inflorescences bear numerous powdery, white colonies. Under favourable environmental conditions the colonies coalesce, host tissue develops chlorosis and usually senesces early. Cleistothecia develop on heavily infected leaves in late summer and are small black/dark brown globose bodies resting on the mycelial surface. Control:, Chemical control and partial genetic resistance. [source] Comparison of dose responses and resistance ratios in four populations of the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), to 20 insecticidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2008Yue Ping He Abstract BACKGROUND: Chemical control is a major strategy for suppressing the rice stem borer, Chilo suppressalis (Walker). Owing to their high toxicity and increasing resistance development in the target insect, many insecticides will be phased out entirely in 2007 in China. Alternatives with relatively low toxicity are urgently needed to replace traditional chemicals for rice stem borer control. In this study, the authors examined four field populations of C. suppressalis for their toxicological responses to more than 20 insecticides, including a few low-toxicity organophosphates and many novel pesticides. Interpopulation resistance levels to 12 conventional insecticides were also compared. RESULTS: Based on LD50 values, the rice stem borer was most sensitive to avermectins and fipronil (LD50 < 1 ng larva,1). The stem borers exhibited the least sensitivity to endosulfan (LD50 > 100 ng larva,1) and monosultap (LD50 > 1000 ng larva,1). Insect growth regulators and chitin synthase inhibitors showed great efficacy against C. suppressalis, especially against populations that had developed resistance to conventional insecticides. Four field populations showed variable tolerance levels to many insecticides. LYG05 was the most susceptible population, only with a low level of resistance to monosultap (RR = 6.6). NC05 and GL05 populations exhibited intermediate tolerance levels with RR values up to 20.4 and 52.8 respectively. RA05 was the most resistant population to many insecticides, with resistance ratios up to 76.2. CONCLUSION: The results from this study provide valuable information for selection and adoption of new alternative insecticides and for resistance management of the rice stem borer. Copyright © 2008 Society of Chemical Industry [source] Distribution of infestation by lentil gall midge Contarinia lentis (Dipt., Cecidomyiidae) in lentil fields: statistical modelJOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2000P. Kolesik The horizontal distribution of infestation by Contarinia lentis in lentil fields, not subjected to chemical control was recorded and analysed in Slovak Republic during outbreaks of this pest in 1986,89. Infestation level was defined as the percentage of galls form the total number of galls, pods, and flowers. The highest level of infestation were found along the edges and the lowest levels in the centres of fields. The distribution of the infestation between the edge and the centre has been described for 18 fields using a nonlinear function containing two parameters. The first parameter represents the infestation level at the edge. The second parameter represents the rate of decreas of infestation from the edge towards the centre of the field. The relationship between the first parameter and the distance to the adult midge emerge site and the relationship between second parameter and the mean velocity of winds caryring females from the emergence site is described using exponential functions. The results indicate that (1) the longer the distance to the midge emergence site, the lower the infestation at the edge; and (2) the gretaer the wind velocity, the weaker the decrese in infestation from the edge towards the centre of a field. [source] Effects of 0.2% chlorhexidine spray applied once or twice daily on plaque accumulation and gingival inflammation in a geriatric populationJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 9 2003Javier Clavero Abstract Background/aims: Chlorhexidine (CHX) spray has proven to be an easily applicable method for the chemical control of plaque in elderly and handicapped patients. A randomized double-blind cross-over placebo-controlled trial was undertaken to compare the effects of 0.2% CHX spray applied once or twice daily on the plaque and gingival indexes in 13 institutionalized elderly patients. Method: The study subjects were randomly assigned to one of two groups. During the first 30-day period, one group received 0.2% chlorhexidine spray twice daily and the other received 0.2% CHX spray once daily plus placebo spray once daily. A washout period of 42 days then followed, after which the groups were interchanged and the process was repeated for another 30-day period. Plaque index and gingival index were determined at the beginning and end of each period. The patients continued with their usual oral hygiene practices throughout the study. Results: A significant reduction in plaque and gingival indexes was produced in both the groups. There were no significant differences in index scores between the groups. Conclusions: The results of the present study suggest that a single-daily application of 0.2% CHX spray is equally as effective in reducing plaque accumulation and gingival inflammation in institutionalized elderly patients as are two-daily applications of the same spray. Zusammenfassung Grundlagen/Ziele: Es hat sich herausgestellt, dass Chlorhexidinspray eine leicht zu handhabende Methode der chemischen Plaquekontrolle bei älteren und behinderten Patienten ist. Um die Unterschiede zwischen ein- oder zweimaliger Applikation von 0.2%-Chlorhexidinspray auf die Plaque- und Gingiva-Indizes zu vergleichen wurde an 13 institutionalisierten älteren Patienten eine randomisierte Plazebo-kontrolierte Crossover-Studie unternommen. Methode: Die Studienteilnehmer wurden randomisiert einer von zwei Gruppen zugeteilt. Während der ersten 30-Tageperiode erhielt eine Gruppe zweimal täglich 0.2%-Chlorhexidinspray und die andere Gruppe einmal täglich 0.2%-Chlorhexidinspray und einmal täglich einen Plazebo-Spray. Es folgte eine Auswaschperiode von 42 Tagen, nach der die Gruppen vertauscht wurden und der Prozess für weitere 30 tage wiederholt wurde. Zu Beginn und am ende einer jeden Periode wurden Plaque-Index (PI) und Gingival-Index (GI) bestimmt. Während der ganzen Studienperiode praktizierten die Patienten ihre üblichen Mundhygienemaßnahmen. Ergebnisse: In beiden Gruppen ergab sich eine signifikante Reduktion der Plaque- und Gingiva-Indizes. Zwischen den beiden Gruppen gab es keine signifikanten Unterschiede der Indexwerte. Schlussfolgerungen: Die Ergebnisse der vorliegenden Studie lassen annehmen, dass bei institutionalisierten älteren Patienten eine einzige Applikation pro Tag von 0.2%-Chlorhexidinspray bei der Reduktion der Plaqueakkumulation sowie der Gingivaentzündung genauso effektiv ist, wie die täglich zweimalige Applikation des gleichen Sprays. Résumé Le spray de chlorhexidine (CHX) a prouvé sa facilité d'application pour le contrôle chimique de la plaque dentaire chez les patients âgés et handicapés. Un essai clinique contrôlé, croisé, en double aveugle, randomisé et placebo-contrôle a été entrepris pour comparer les effets d'un spray de CHX 0.2% appliqué une ou deux fois par jour sur la plaque dentaire et les indices gingivaux de patients âgés de douze institutions. Les sujets ont été répartis en deux groupes. Durant une première période de 30 jours, un groupe recevait un spray de CHX 0.2% deux fois par jour tandis que l'autre recevait un spray de CHX 0.2% un fois par jour plus un spray placebo une fois par jour. Une période sans traitement de 42 jours a ensuite étéétablie suivie à la suite de laquelle les groupes ont été interchangés et le processus répété pour une nouvelle période de 30 jours. L'indice de plaque dentaire et l'indice gingival ont été déterminés au début et à la fin de chaque période. Les patients ont continué leurs habitudes d'hygiène buccale habituelles durant toute l'étude. Une réduction significative des indices de plaque et de gencive ont été relevés dans les deux groupes. Il n'y avait aucune différence significative de scores entre les deux groupes. Les résultats de l'étude présente suggèrent qu'une application unique d'un spray de CHX 0.2% est tout aussi efficace dans la réduction de la plaque dentaire et l'inflammation gingivale chez les patients âgés qu'une double application du même spray. [source] Genetic diversity in pollen beetles (Meligethes aeneus) in Sweden: role of spatial, temporal and insecticide resistance factorsAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2007Nadiya Kazachkova Abstract 1,Pollen beetles Meligethes aeneus are pests of oilseed Brassica crops that are subject to intensive chemical control. Resistance to pyrethroids has been reported. Although this insect is of great economic importance, little is known about its genetic properties and population structure. 2,Amplified fragment length polymorphism (AFLP) analysis with the restriction endonuclease combination EcoRI and PstI was performed on 133 samples of groups of three pollen beetles collected during 2001,04 from five different provinces of Sweden. Both susceptible and resistant insects were studied. Using one primer combination, more than 450 polymorphic DNA fragments were obtained and, in total, four primer combinations were used for analysis. A subsample of 59 single beetles was analysed using one primer combination. 3,AFLP profiles were analysed by similarity measures using the Nei and Li coefficient and Neighbour-joining dendrograms were generated. The dendrogram built using 133 samples showed three distinct groups, each containing beetles representing one generation. Statistical analysis using analysis of molecular variance of single beetle samples showed no evidence of significant genetic difference between resistant and susceptible beetles. Instead, a clear difference between samples, depending on time of collection and generation, was observed. 4,The expected regional population structure, although statistically significant, explained little of the variation. The levels of genetic variation within populations were very high. There appears to be a high rate of gene flow between pollen beetle populations. The implications of this in the context of insecticide resistance are discussed. [source] Potential of Trichoderma harzianum and T. atroviride to Control Botryosphaeria berengeriana f. sp. piricola, the Cause of Apple Ring RotJOURNAL OF PHYTOPATHOLOGY, Issue 4-5 2002G. KEXIANG Abstract Trichoderma harzianum T88 and T. atroviride T95 were tested for their efficacy in controlling apple ring rot (caused by Botryosphaeria berengeriana f. sp. piricola) in vitro and in the field. Isolates of T88 and T95 produced both volatile and non-volatile antibiotics that suppressed mycelial growth of the pathogen. Light and scanning electron microscopy showed that mycoparasitism by Trichoderma spp. of B. berengeriana f. sp. piricola resulted in penetration and disruption of hyphal cells, and thinning of cytoplasm of the pathogen. The culture filtrates of T88 and T95 in Czapek's liquid medium suppressed conidial germination of the pathogen, and the germination level was negatively correlated with the duration of culture of Trichoderma. In inoculation tests, 32 days after simultaneous inoculation or preinoculation with B. berengeriana f. sp. piricola and Trichoderma spp., the incidence of infected apple shoots was reduced, respectively, by 65.3,76.4% and 62.5,76.4%, and the index of infection reduced by 36.9,38.9 and 40.7,44.4, The effect of inoculating B. berengeriana f. sp. piricola 3 days after the antagonists were inoculated was greater (81.4,88.8%) than simultaneous inoculation (72.2,77.8%). Re-isolation from inoculated apple shoots demonstrated that the pathogen had been suppressed by Trichoderma. The ability to re-isolate the pathogen from apple after co-inoculation and pre-inoculation with Trichoderma spp. was reduced by 27.0,42.3% and 22.2,47.1%, respectively. The biocontrol field trial suggested that the B. berengeriana f. sp. piricola canker on apple shoots and stems and rotting fruit had been efficiently controlled by the application of spore suspensions of T. harzianum T88 and T. atroviride T95. The efficacy of control by Trichoderma is thus similar to that of routine chemical control. [source] Accumulated thermal time, a key factor in affecting generation initiation and duration of top borer, Scirpophaga excerptalis Walker of sugarcane for its model-based chemical controlMETEOROLOGICAL APPLICATIONS, Issue 1 2010Arun K. Srivastava Abstract The seasonal variation in the initiation and duration of the I,III generations of the top borer was observed and analysed during five crop cycles from 2002,2003 to 2006,2007 at Lucknow in central Uttar Pradesh. The durations of the I,III generations were significantly correlated with the accumulated thermal time (Tbase = 10°C). Relatively higher temperature and consequently higher accumulated thermal time shortened the brood duration and early initiation of successive generations and vice versa. Based on these correlations, models were developed for predicting the initiation and duration of these generations. These models were validated for 2007,2008 crop cycle. The differences between observed and predicted duration of the I,III generation of the pest were 3, 1 and 3 days respectively reflecting high precision of the models. As the current management strategy for the chemical control of the pest is based on a calendar week, the shift of III generation initiation due to seasonal fluctuations could lead to escape from insecticide and render the chemical application pointless. The model-based control strategy is more precise and foretells the time of application of chemical against III generation of top borer which is most damaging to sugarcane crop. Copyright © 2009 Royal Meteorological Society [source] Root-knot nematode parasitism and host response: molecular basis of a sophisticated interactionMOLECULAR PLANT PATHOLOGY, Issue 4 2003Pierre Abad SUMMARY Taxonomy: Eukaryota; Metazoa; Nematoda; Chromadorea; order Tylenchida; Tylenchoidea; Heteroderidae; genus Meloidogyne. Physical properties: Microscopic-non-segmented worms. Meloidogyne species can reproduce by apomixis, facultative meiotic parthenogenesis or obligate mitotic parthenogenesis. Obligate biotrophic parasites inducing the re-differentiation of plant cells into specialized feeding cells. Hosts: Meloidogyne spp. can infest more than 3000 plant species including vegetables, fruit trees, cereals and ornamental flowers. Symptoms: Root swellings called galls. Alteration of the root vascular system. Disease control: Cultural control, chemical control, resistant cultivars. Agronomic importance: Major threat to agriculture in temperate and tropical regions. [source] Strategies for development of vaccines for control of ixodid tick speciesPARASITE IMMUNOLOGY, Issue 7 2006J. DE LA FUENTE SUMMARY Ticks are distributed worldwide and impact human and animal health, as well as food animal production. Control of ticks has been primarily by application of acaricides, which has resulted in selection of resistant ticks and environmental pollution. Vaccines have been shown to be a feasible tick control method that offers a cost-effective, environmentally friendly alternative to chemical control. However, identification of tick-protective antigens remains the limiting step in vaccine development. Tick antigens exposed naturally to the host during tick feeding and those concealed have both shown promise as candidate vaccine antigens. Development of vaccines against multiple tick species may be possible using highly conserved tick-protective antigens or by antigens showing immune cross-reaction to different tick species. Vaccines made from a combination of key protective antigens may greatly enhance vaccine efficacy. Preliminary studies have suggested the possibility of vaccine strategies directed toward both tick control and the blocking of pathogen transmission. Characterization of the tick genomes will have a great impact on the discovery of new protective antigens. The future of research directed toward tick vaccine development is exciting because of new and emerging technologies for gene discovery, and vaccine formulation and delivery. [source] Abnormalities of the chemical control of breathing: Clinical correlates in infants and childrenPEDIATRIC PULMONOLOGY, Issue S23 2001Dr. Claude Gaultier First page of article [source] Abnormalities of the chemical control of breathing: Clinical correlates in infants and childrenPEDIATRIC PULMONOLOGY, Issue S23 2001Dr. Claude Gaultier First page of article [source] Toxicity of insecticides to the sweetpotato whitefly (Hemiptera: Aleyrodidae) and its natural enemiesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2007Leandro Bacci Abstract Efficient chemical control is achieved when insecticides are active against insect pests and safe to natural enemies. In this study, the toxicity of 17 insecticides to the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the selectivity of seven insecticides to natural enemies of this insect pest were evaluated. To determine the insecticide toxicity, B. tabaci adults were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion, methamidophos, bifenthrin, cypermethrin, deltamethrin, esfenvalerate, fenitrothion, fenpropathrin, fenthion, phenthoate, permethrin and trichlorphon at 50 and 100% of the field rate (FR), and to water (untreated control). To determine the insecticide selectivity, adults of Encarsia sp., Acanthinus sp., Discodon sp. and Lasiochilus sp. were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion and methamidophos at 50 and 100% FR, and to water. Groups of each insect species were exposed to kale leaves preimmersed in each treatment under laboratory conditions. Mortality of exposed individuals was recorded 24 h after treatment. Cartap and imidacloprid at 50 and 100% FR and abamectin and acetamiprid at 100% FR showed insecticidal activity to B. tabaci adults. Abamectin at 50 and 100% FR was the least insecticidal compound to the natural enemies Acanthinus sp., Discodon sp. and Lasiochilus sp. The present results suggest that abamectin at 100% FR may decrease B. tabaci field populations but can still be harmless to predators. Implications of these results within an integrated pest management context are discussed. Copyright © 2007 Society of Chemical Industry [source] United States Department of Agriculture,Agricultural Research Service research on pest biology: weeds,,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 6-7 2003Frank Forcella Abstract Over 125 permanent full-time scientists conduct research within the USDA Agricultural Research Service (ARS) on issues related to weeds. The research emphasis of most of these scientists involves ecology and management or biological control of weeds. Many scientists perform research on weed biology as components of their primary projects on weed control and integrated crop and soil management. Describing all ARS projects involved with weed biology is impossible, and consequently only research that falls within the following arbitrarily chosen topics is highlighted in this article: dormancy mechanisms; cell division; diversity of rangeland weeds; soil resources and rangeland weeds; poisonous rangeland plants; horticultural weeds; weed traits limiting chemical control; aquatic and semi-aquatic weeds; weed/transgenic wheat hybrids; seedbanks, seedling emergence and seedling populations; and weed seed production. Within these topics, and others not highlighted, the desire of ARS is that good information on weed biology currently translates or eventually will translate into practical advice for those who must manage weeds. Published in 2003 for SCI by John Wiley & Sons, Ltd. [source] Economic management of anthelmintic resistance: model and application,AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 4 2009Caris L. Pech The increasing prevalence of anthelmintic (drench) resistance in gastrointestinal parasite populations is decreasing the profitability of the Australian sheep industry. Refugia management can delay its development by not exposing a proportion of the worm population to chemical control. A dynamic-optimisation model is used to assess the economic value of refugia for management of the worm species Teladorsagia circumcincta and macrocyclic lactone drenches in an application to Western Australian sheep flocks. A low rate of refugia (2 per cent) is most profitable under standard circumstances because it slows the development of resistance, but also reduces the proportion of the flock not exposed to chemical control. Frequent drench application should remain the primary method of control. However, its efficacy should be preserved through refugia management, rather than greatly reducing treatment frequency. [source] Microarray analysis yields candidate markers for rotation resistance in the western corn rootworm beetle, Diabrotica virgifera virgiferaEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 1 2010Lisa M. Knolhoff Abstract As pest species may evolve resistance to chemical controls, they may also evolve resistance to cultural control methods. Yearly rotation of corn (Zea mays) with another crop interrupts the life cycle of the western corn rootworm beetle (Diabrotica virgifera virgifera, Coleoptera: Chrysomelidae), but behavioral resistance to crop rotation is now a major problem in the Midwest of the USA. Resistant adult females exhibit reduced fidelity to corn as a host and lay their eggs in the soil of both corn and soybean (Glycine max) fields. Behavioral assays suggest that the adaptation is related to increased locomotor activity, but finding molecular markers has been difficult. We used microarray analysis to search for gene expression differences between resistant and wild-type beetles. Candidates validated with real-time polymerase chain reaction exhibit predicted patterns from the microarray in independent samples across time and space. Many genes more highly expressed in the rotation-resistant females have no matches to known proteins, and most genes that were more lowly expressed are involved in antimicrobial defense. [source] | |||||||||||||||||||