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Laboratory Bioassays (laboratory + bioassay)
Selected AbstractsAcaricidal activity against Panonychus citri of a ginkgolic acid from the external seed coat of Ginkgo bilobaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2006Weigao Pan Abstract An acaricidal substance extracted from the external seed coat of Ginkgo biloba L. was identified by UV (ultraviolet), IR (infrared), EI-MS (electron impact ion source mass spectrometry), 1H NMR (nuclear magnetic resonance) and 13C NMR as 6-[(Z)-10-heptadecenyl]-2-hydroxybenzoic acid (compound 1). Laboratory bioassay on citrus red mite, Panonychus citri (Mcg), showed that compound 1 possessed the following properties. (i) Powerful contact toxicity with an LC50 of 5.2 mg litre,1 after 24 h that was similar to that of pyridaben (LC50 = 3.4 mg litre,1) and significantly superior to that of omethoate (LC50 = 122 mg litre,1). Furthermore, its LC90 was 13.4 mg litre,1 after 24 h, which is significantly superior to both pyridaben (LC90 = 69.6 mg litre,1) and omethoate (LC90 = 453 mg litre,1). (ii) Quick-acting acaricidal activity. At identical concentrations, compound 1 was much faster-acting than pyridaben or omethoate. (iii) Compound 1 had strong corrosive action on the cuticle of P. citri but no phytotoxicity to plants. Copyright © 2006 Society of Chemical Industry [source] Prior encounters modulate subsequent choices in host acceptance behavior by the bark beetle Ips piniENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Kimberly F. Wallin Abstract Laboratory bioassays indicate that the bark beetle Ips pini employs flexible, rather than absolute, responses to phytochemicals in its host acceptance behavior. Each beetle's decision to enter substrate was influenced by the types and concentrations of monoterpenes present. However, previous rejection of a simulated host containing a moderate concentration of monoterpenes increased the likelihood that the same concentration would be accepted upon a second or third encounter. This flexibility more than offsets any loss of vigor due to starvation and age that accompanies a process of trial and error. Starvation decreased beetles' total lipid content, but beetles can recover some energetic losses by a small amount of feeding during each trial. In addition to its adaptive value, a flexible host acceptance strategy may yield population level consequences. That is, bark beetles preferentially enter trees having low concentrations of monoterpenes, but may modify their acceptance thresholds when cues associated with stressed trees are not available. This could partially explain how some tree-killing bark beetles colonize a broader physiological range of trees during outbreaks. The adaptive value of relating individual decisions to population density may arise from two ecological relationships: first, as populations rise, the pool of stressed trees is rapidly depleted; secondly, healthy trees are attainable through pheromone , mediated mass attacks when adequate numbers of beetles are present. Flexible host acceptance behaviors may also reduce the advantage of relying exclusively on pre-landing cues to distinguish between susceptible and non-susceptible trees. [source] Effect of varying pesticide exposure duration and concentration on the toxicity of carbaryl to two field-collected stream invertebrates, Calineuria californica (Plecoptera: Perlidae) and Cinygma sp. (Ephemeroptera: Heptageniidae)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Jennifer L. Peterson Abstract The effect of exposure duration on the toxicity of a forest insecticide (carbaryl) was assessed under environmentally realistic exposure regimes against two stream invertebrates indigenous to the United States Pacific Northwest, Calineuria californica (Plecoptera: Perlidae) and Cinygma sp. (Ephemeroptera: Heptageniidae). Laboratory bioassays were conducted to evaluate the relationship between pulsed exposures of 15, 30, and 60 min and toxicity for a range of chemical concentrations (10.2,1,730 ,g/L). For Cinygma sp., the 50% lethal concentration (LC50) values were calculated as 848 ,g/L (15 min), 220 ,g/L (30 min), and 165 ,g/L (60 min). The C. californica consistently had lower mortality at a given concentration compared with Cinygma sp. Fifteen- and 30-min exposures did not elicit 50% mortality with C. californica, and it had a 60-min LC50 of 1,139 ,g/L. Time to 50% mortality over 96 h after a 15-, 30-, or 60-min exposure, with the rest of the test period in freshwater (PLT50), was a function of exposure duration and concentration. Analysis of symptomology throughout the test period for C. californica gave evidence of recovery from the knockdown and moribund states, but this was not the case for Cinygma sp. The pulse duration resulting in 50% mortality was calculated as 43 min for Cinygma sp. exposed at 204 ,g/L and 16 min at 408 ,g/L. A three-dimensional probit plane model [Y = , 10.86 + 4.83(In C) + 3.0(In T)], where Y is probit mortality, C is concentration in ,g/L and T is time in hours, was used to explain the interaction between concentration (,g/L) and duration of exposure (hours) for Cinygma sp. [source] Effect of five diatomaceous earth formulations against Tribolium castaneum (Coleoptera: Tenebrionidae), Oryzaephilus surinamensis (Coleoptera: Silvanidae) and Rhyzopertha dominica (Coleoptera: Bostrychidae)INSECT SCIENCE, Issue 5 2007MASUMEH ZIAEE Abstract Laboratory bioassays were conducted to determine the effect of food source on the survival of Tribolium castaneum Herbst, Oryzaephilus surinamensis L. and Rhyzopertha dominica F., after exposure to five diatomaceous earth (DE) formulations: Protect-It®, Insecto®, Perma-GuardÔ, Dryacide® and SilicoSec®. Adults of these species were exposed to DEs at the rate of 0.5 mg/cm2 for 1 day on filter paper inside plastic Petri dishes. After exposure, the initial mortality was counted and live individuals of the three species were held for a week in glass vials containing 50 mg wheat flour, rice and whole wheat, respectively. In the second experiment, after 1 day exposure to DEs, beetles were transferred to Petri dishes without food and held for a week to determine if the presence of food source would decrease the mortality of beetles. Experiments were carried out at 27°C and 55% RH in the dark. The initial mortality in both of the experiments reached 100% for the three species exposed to Protect-It® and in the case of R. dominica and O. surinamensis exposed to Dryacide®. In contrast, low level of mortality (< 10%) was observed for T. castaneum exposed to Perma-GuardÔ and Insecto®. The mortality after the post-treatment period on food was decreased for the three species exposed to Perma-GuardÔ and in the case of T. castaneum and R. dominica exposed to Insecto® and SilicoSec®. Adults of O. surinamensis were the most susceptible followed by R. dominica and 100% adult mortality was obtained, whereas T. castaneum were the least susceptible beetles to DEs. Protect-It® and Dryacide® were the most efficient DE formulations and can be used effectively in a stored grain integrated pest management program. [source] Field efficacy of transgenic cotton containing single and double toxin genes against the Asian corn borer (Lep., Pyralidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2004K. He Abstract:, Insect resistant transgenic cotton (Gossypium hirsutum L.) is expected to provide satisfactory control of lepidopteran species in the cotton field. The Asian corn borer, Ostrinia furnacalis (Guenée) (Lep., Pyralidae), is an important component of the lepidopteran pest complex of cotton in China. Insect resistant transgenic cotton cultivars GK2, carrying cry1A gene, and SGK321, carrying both cry1A and CpTI genes, were evaluated for resistance to Asian corn borer. Field trials were conducted with artificial infestation of Asian corn borer at squaring, flowering and flowering-boll cotton plants, which coincided with the generations of natural Asian corn borer occurrence. Damage ratings were significantly reduced in transgenic cotton cultivars both GK2 and SGK321 compared with their parental non-transgenic cotton cultivars Simian3 and Shiyuan321, respectively. In addition, percentage of plants stem bored and number of tunnels per plant were significantly higher on GK2 than on SGK321 in the second generation. Laboratory bioassays were carried out by exposing neonates to plant tissues collected from the field. Tissues assayed included the new leaves, match-head squares and white flowers, which are the tissues initially attacked by the neonates in the field. Low larval survival rates were observed on SGK321 and GK2, contrasting greatly to the high number of survivors found on their non-transgenic cotton tissue isolated throughout the season. However, larval survival was higher on new leaves isolated from late-season transgenic cotton plants and fruit tissues than on early-season. In addition, higher larval survival was observed on GK2 than SGK321 in assays with the late season tissues. This may be associated with reduced levels of available toxin in plant tissues as they age. Both laboratory and field data indicated that SGK321 and GK2 were highly resistant to Asian corn borer. The high level of efficacy for insect resistant transgenic cotton against Asian corn borer offers the potential for season-long control. [source] Attract-and-kill strategy.PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2007Laboratory studies on hatched larvae of Culex pipiens Abstract The attract-and-kill strategy is a new pest management technique that presupposes the intelligent combination of an attracting agent (e.g. pheromone) and a killing agent (e.g. insecticide). In the present study, the potential combination of the microencapsulated synthetic oviposition pheromone 6-acetoxy-5-hexadecanolide with an insecticide has been tested. Initially, polyurea microcapsules containing 6-acetoxy-5-hexadecanolide, the synthetic mixture of diastereomers of the oviposition pheromone of the mosquito species Culex quinquefasciatus Say (Diptera: Culicidae), were studied. Laboratory bioassays were performed to confirm the bioactivity of the microencapsulated pheromone on the oviposition activity of Culex pipiens L. biotype molestus Førskal (Diptera: Culicidae) with the aim of determining the optimum dose for oviposition response. Its effect was dose dependent, revealing an optimum dose of 300 mg of dried microcapsules. Attractancy over time was also studied. The microencapsulated pheromone was found to be sufficiently attractive to gravid female mosquitoes for a period of 40 days. Finally, the combination of the synthetic pheromone with the control agent temephos showed both an acceptable oviposition activity and sufficient larvicidal effect. Copyright © 2007 Society of Chemical Industry [source] Insecticidal, antifeedant and oviposition deterrent effects of the essential oil and individual compounds from leaves of Chloroxylon swietenia DC.PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2006S Ravi Kiran Abstract Essential oil from the leaves of Chloroxylon swietenia DC. was obtained by hydrodistillation and cold extraction, and the chemical composition was determined by gas chromatography and gas chromatography-mass spectrometry. The major identified components were limonene, geijerene, pregeijerene, germacrene D and trans-,-ocimene. Laboratory bioassays of the essential oil and four constituents of essential oil isolates were evaluated for insecticidal, antifeedant and oviposition deterrent effects on tobacco cutworm, Spodoptera litura (F.). Toxicity was determined by topical application of the isolates at varying concentrations. Pure oil, geijerene and pregeijerene were found to be more toxic, with LD50 values of 28.6, 35.4 and 40.7 µg per larva respectively. Maximum feeding deterrence was noted for geijerene and pregeijerene, with DC50 values of 82.5 and 95.1 µg cm,2 respectively. Furthermore, pure oil, geijerene and pregeijerene displayed oviposition deterrence, even at low concentrations. These results indicate that these natural products may lead to useful, biodegradable, environmentally safe insect control agents. Copyright © 2006 Society of Chemical Industry [source] Genetics of spinosad resistance in a multi-resistant field-selected population of Plutella xylostellaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2004Ali H Sayyed Abstract Resistance to the bacteria-derived insecticides spinosad (Conserve), abamectin (Vertimec), Bacillus thuringiensis var kurstaki (Btk) (Dipel), B thuringiensis var aizawai (Bta) (Xentari), B thuringiensis crystal endotoxins Cry1Ac and Cry1Ca, and to the synthetic insecticide fipronil was estimated in a freshly-collected field population (CH1 strain) of Plutella xylostella (L) from the Cameron Highlands, Malaysia. Laboratory bioassays at G1 indicated significant levels of resistance to spinosad, abamectin, Cry1Ac, Btk, Cry1Ca, fipronil and Bta when compared with a laboratory insecticide-susceptible population. Logit regression analysis of F1 reciprocal crosses indicated that resistance to spinosad in the CH1 population was inherited as a co-dominant trait. At the highest dose of spinosad tested, resistance was close to completely recessive, while at the lowest dose it was incompletely dominant. A direct test of monogenic inheritance based on a back-cross of F1 progeny with CH1 suggested that resistance to spinosad was controlled by a single locus. Copyright © 2004 Society of Chemical Industry [source] Leaf surfaces and the bioavailability of pesticide residuesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2001M Nasir U Chowdhury Abstract Laboratory bioassays were carried out to determine the toxicity to Folsomia candida Willem (Collembola: Isotomidae) of residues of a pyrethroid insecticide, deltamethrin, and an organophosphorus insecticide, dimethoate, on different leaf surfaces. The test leaves included a range of species and leaves of different ages. Dose-response relationships were estimated for F candida walking over the various treated leaf substrates. Probit analysis was used to estimate the means and standard deviations of the associated tolerance distributions expressed as g,AI,ha,1. Parallelism tests were undertaken to compare the susceptibilities of F candida to the two compounds applied to the different leaf surfaces. On deltamethrin-treated leaf surfaces, the LD50 values for F candida varied from 6.36 to 77.14,g,AI,ha,1. F candida was least susceptible to deltamethrin residues when applied to leaves of dwarf bean (Phaseolus vulgarus L) and the highest susceptibility was observed following application to leaves of seedlings of barley (Hordeum vulgare L). In contrast, the LD50 values observed for dimethoate treatments did not differ significantly between leaf types, ranging from 1.35 to 8.69,g,AI,ha,1. The laboratory data on susceptibility of F candida on different leaf types for different pesticides can be used to investigate the role of leaf surface properties in modifying the toxicity of applied pesticides to exposed invertebrates. © 2001 Society of Chemical Industry [source] Evaluation of existing and new insecticides including spirotetramat and pyridalyl to control Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on peppers in QueenslandAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 2 2010Iain R Kay Abstract Insecticides are used by growers to control Frankliniella occidentalis (western flower thrips) in Australian vegetable crops. However, limited information was available on the efficacy of some insecticides used against F. occidentalis and data on new insecticides that could be included in a resistance management program were required. The efficacy of 16 insecticides in controlling F. occidentalis was tested in four small plot trials in chillies and capsicums. Spinosad, fipronil and methamidophos were effective against adults and larvae. Spirotetramat had no efficacy against adults but was very effective against larvae. Pyridalyl was moderately effective against larvae. Methidathion showed limited effectiveness. Abamectin, amorphous silica, bifenthrin, chlorpyrifos, dimethoate, emamectin benzoate, endosulfan, imidacloprid, methomyl and insecticidal soap were not effective. Laboratory bioassays on F. occidentalis collected from the field trials showed resistance to bifenthrin but not to the other insecticides tested. The trials demonstrated that some insecticides permitted for use against F. occidentalis are not effective and identified a number of insecticides, including the new ones spirotetramat and pyridalyl, that are effective and that could be used to manage the pest within a resistance management program. [source] Effects of bio-pesticides on Eretmocerus warrae (Hym., Aphelinidae), a parasitoid of Bemisia tabaci (Hom., Aleyrodidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2008P. Kumar Abstract The sweet potato whitefly Bemisia tabaci (WF) can be controlled by two commercial neem products, NeemAzal-T/S® (1% azadirachtin) for foliar application, and NeemAzal-U (17% azadirachtin) for soil application, alongwith two biorational products of microbial origin, Abamectin (avermectin) and Success® (spinosad). Side effects of these products were tested in a laboratory bioassay against a native aphelinid, Eretmocerus warrae (EW). Eggs and early larval instars of the parasitoid, commonly found outside the host body, were highly susceptible to foliar spray of neem with only 8%, 18% and 55% emergences of adults from treated eggs. larval and pupal stages respectively at recommended dose-rates of 5 ml/l and 1%, 8% and 40% at twice recommend dose-rate (10 ml/l). Soil application with NeemAzal-U marginally affected EW. At highest tested dose-rate of 3.0 g/l, 46%, 64% and 81% emergence was recorded after treatement of plants harbouring WF parasitized by egg, larval and pupal stages of EW respectively. In contrast to neem application, Success® and Abamectin caused high mortality in development stages of the parasitoids. In particular, abamectin was highly toxic to the parasitoids with less than 1% emergence from either of the three development stages if treated with 1,2 ml/l. [source] Insecticidal activities of secondary metabolites of endophytic Pencillium sp. in Derris elliptica BenthJOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2005M. Y. Hu Abstract:, A strain of endophytic Pencillium sp., which might produce rotenone or its analogues and showed bioactivity against aphids, was isolated from the fresh roots of Derris elliptica Benth. A total of 12 fractions, isolated from the chloroform extract of endophytic Pencillium sp. mycelia by silica gel column, were tested by bioassay and high-performance liquid chromatography (HPLC), and the more bioactive fractions were found to be D, E and J. Against the adult turnip aphid, Lipaphis erysimi, by dipping at a concentration of 1 mg/ml, the corrected mortalities of fraction D, E and J were 57.68, 63.28 and 69.74% after 48 h of treatment respectively. The three fractions also showed strong antifeeding activity against third instar larvae of Plutella xylostella in a laboratory bioassay. One absorption peak was detected in the HPLC picture of fraction D, it had a similar retention time as that of rotenone, and the chemical constituent, related to the absoption peak, had the same ultraviolet absorption picture as that of rotenone. Then it could be further concluded that the bioactive compounds in the fraction D could be rotenone or its analogous compounds. [source] Resource allocation to defence and growth are driven by different responses to generalist and specialist herbivory in an invasive plantJOURNAL OF ECOLOGY, Issue 5 2010Wei Huang Summary 1.,Invasive plants often have novel biotic interactions in their introduced ranges. These interactions, including less frequent herbivore attacks, may convey a competitive advantage over native plants. Invasive plants may vary in defence strategies (resistance vs. tolerance) or in response to the type of herbivore (generalists vs. specialists), but no study to date has examined this broad set of traits simultaneously. 2.,Here, we examined resistance and tolerance of Chinese tallow (Triadica sebifera) populations from the introduced and native ranges to generalist (Cnidocampa flavescens) and specialist herbivores (Gadirtha inexacta) in the native range. 3.,In a field common-garden test of resistance, caterpillars of each species were raised on plants from native and invasive populations. We found the specialist grew larger on and consumed more mass of invasive plant populations than native populations, while the generalist showed the same performance between them. The results were consistent with our laboratory bioassay using excised leaves. Chemical analyses showed that the invasive plants had lower tannin content and higher ratio of carbohydrate to protein than those of their native counterparts, suggesting that plants from invasive populations have altered chemistry that has a larger impact on specialist than on generalist resistance. 4.,To test for differences in herbivore tolerance, plants were first defoliated by specialist or generalist herbivory and then allowed to regrow for 100 days in a field common garden. We found that plants from invasive populations had greater herbivore tolerance than native populations, especially for tolerance to generalists. They also grew more rapidly than native counterparts in the absence of herbivory. 5.,Synthesis. The results of these experiments indicate that differences in selective pressures between ranges have caused dramatic reductions in resistance to specialist herbivores and those changes in plant secondary chemistry likely underlie these differences. The greater tolerance of invasive populations to herbivory appears to at least partly reflect an increase in growth rate in the introduced range. The greater tolerance to generalist herbivores suggests the intriguing possibility of selection for traits that allow plants to tolerate generalist herbivores more than specialist herbivores. [source] Bioassay and Identification of Root Exudates of Three Fruit Tree SpeciesJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 3 2007Jiang-Hong Zhang Abstract A laboratory bioassay was designed to determine the allelopathic potential of root exudates of three fruit tree species on apple germination. The results showed that root exudates of apple (Malus pumila L.) and peach (Prunus persica L.), each at concentrations of 0.02 and 0.2 mg/L, inhibited germination and radicle growth of apple seeds by 56.7%, 60.7%, 51.5%, and 59.3%, respectively. The corresponding shoot growth inhibition rate was 49.5%, 46.7%, 36.4%, and 44%, respectively. Root exudates of jujube (Ziziphus jujuba Mill.) had no significant effect on apple seeds. Qualitative determination of root exudates of apple, peach, and jujube tree was developed with gas chromatography-mass spectrometry. The root exudates of apple seedlings mainly contain organic acids, glycol, esters, and benzenphenol derivatives. Peach root exudates contained phenolic acids and benzenphenol derivatives in addition to two unidentified compounds. The root exudates of jujube did not contain any phenolic acids. [source] Uptake, translocation and bioavailability of imidacloprid in several hop varietiesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2004Lars Weichel Abstract The neonicotinoid insecticide imidacloprid is the most important insecticide in hop cultivation in Germany. A laboratory study was undertaken to investigate its systemic properties and translaminar bioavailability in hop leaves. Radiolabelled [methylene - 14C]imidacloprid was applied either alone or in combination with different additives onto leaves of several hop varieties. Uptake and translocation were evaluated 1 and 7 days after foliar application under greenhouse conditions. The uptake of imidacloprid into hop leaves was most pronounced in the first 24 h after application and only negligible amounts were taken up after this period. Significant differences in the quantitative uptake occurred when imidacloprid was combined with additives, such as Amulsol, Genapol C-100, Hasten and LI 700. The uptake of imidacloprid applied without additives was less than 10% 7 days after application, whereas the combination with LI 700 provided 70,80% uptake. Genapol C-100 and Amulsol induced considerable phytotoxicity at the application site. Comparing hop varieties revealed differences up to twofold in foliar penetration of imidacloprid. The translaminar and acropetal bioavailability of imidacloprid foliarly applied to hop leaves was determined by a laboratory bioassay using the damson hop aphid, Phorodon humuli (Schrank). Significantly higher mortality was observed with laboratory formulations containing imidacloprid and the additive LI700. In contrast to these results from systemic tests, contact mortality at the application site was constantly high over the testing period of 7 days, highlighting the importance of this mode of entry for aphid intoxication. Copyright © 2003 Society of Chemical Industry [source] Australian populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), are resistant to some insecticides used for their controlAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008Grant A Herron Abstract Onion thrips, Thrips tabaci Lindeman, is a major pest of Australian field onion Allium cepa Linnaeus with their control heavily reliant on a few insecticides. An earlier study after grower complaints of control failures did not detect resistance in three populations. After testing an additional nine populations via a Potter spray tower laboratory bioassay unequally against ,-cypermethrin, diazinon, dimethoate, ,-cyhalothrin, malathion and methidathion, we document resistance in T. tabaci for the first time in Australia. The maximum difference in response (resistance) for each insecticide was detected by dividing the most resistant LC50 response by the least resistant LC50 response. Comparison of the most susceptible to the least susceptible population tested produced ,-cypermethrin and ,-cyhalothrin resistance at 164- and 606-fold, respectively. Diazinon and dimethoate resistance was also detected at 27-fold and 5.2-fold respectively although omethoate, malathion and methidathion resistance were not detected. [source] Influence of in-stream diel concentration cycles of dissolved trace metals on acute toxicity to one-year-old cutthroat trout (Oncorhynchus clarki lewisi)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2007David A. Nimick Abstract Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining-affected streams compared the survival of hatchery-raised, metal-näive westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0.1-,m filtration) metal concentrations that either exhibited the diel variation observed in streams or were controlled at a constant value. Cadmium and Zn concentrations in these streams increased each night by as much as 61 and 125%, respectively, and decreased a corresponding amount the next day, whereas Cu did not display a diel concentration cycle. In High Ore Creek (40 km south of Helena, MT, USA), survival (33%) after exposure to natural diel-fluctuating Zn concentrations (range, 214,634 ,g/L; mean, 428 ,g/L) was significantly (p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 ,g/L). Similarly, in Dry Fork Belt Creek (70 km southeast of Great Falls, MT, USA), survival (75%) after exposure to diel-fluctuating Zn concentrations (range, 266,522 ,g/L; mean, 399 ,g/L) was significantly (p = 0.022) higher than survival (50%) in the constant-concentration treatment (392 ,g/L). Survival likely was greater in these diel treatments, both because the periods of lower metal concentrations provided some relief for the fish and because toxicity during periods of higher metal concentrations was lessened by the simultaneous occurrence each night of lower water temperatures, which reduce the rate of metal uptake. Based on the present study, current water-quality criteria appear to be protective for streams with diel concentration cycles of Zn (and, perhaps, Cd) for the hydrologic conditions tested. [source] In situ and laboratory bioassays with Chironomus riparius larvae to assess toxicity of metal contamination in rivers: The relative toxic effect of sediment versus water contaminationENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2007Mafalda S. Faria Abstract We used bioassays employing head capsule width and body length increase of Chironomus riparius larvae as end points to evaluate metal contamination in streams. Bioassays were performed in situ near an abandoned Portuguese goldmine in the spring of 2003 and 2004. Bioassays also were performed under laboratory conditions with water and sediment collected from each stream to verify if laboratory bioassays could detect in situ toxicity and to evaluate the relative contribution of sediment and water to overall toxicity. We used field sediments with control water and control sediments with field water to discriminate between metal contamination in water and sediment. Field water with dry and sieved, organic matter,free, and nontreated sediments was used to determine the toxicity of heavy metals that enter the organism through ingested material. In both in situ and laboratory bioassays, body length increase was significantly inhibited by metal contamination, whereas head capsule width was not affected. Body length increase was more affected by contaminated sediment compared to contaminated water. The lowest-effect level of heavy metals was observed in the dry and sieved sediment that prevented ingestion of sediment particles by larvae. These results suggest that body length increase of C. riparius larvae can be used to indicate the impact of metal contamination in rivers. Chironomus riparius larvae are more affected by heavy metals that enter the organism through ingested sediment than by heavy metals dissolved in the water column. Nevertheless, several factors, such as the particle size and organic matter of sediment, must be taken into account. [source] Risk of weathered residual Exxon Valdez oil to pink salmon embryos in Prince William SoundENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2007Ernest L. Brannon Abstract It has been hypothesized that pink salmon eggs incubating in intertidal streams transecting Prince William Sound (PWS) beaches oiled by the Exxon Valdez oil spill were exposed to lethal doses of dissolved hydrocarbons. Since polycyclic aromatic hydrocarbon (PAH) levels in the incubation gravel were too low to cause mortality, the allegation is that dissolved high-molecular-weight hydrocarbons (HPAH) leaching from oil deposits on the beach adjacent to the streams were the source of toxicity. To evaluate this hypothesis, we placed pink salmon eggs in PWS beach sediments containing residual oil from the Exxon Valdez oil spill and in control areas without oil. We quantified the hydrocarbon concentrations in the eggs after three weeks of incubation. Tissue PAH concentrations of eggs in oiled sediments were generally <100 ppb and similar to background levels on nonoiled beaches. Even eggs in direct contact with oil in the sediment resulted in tissue PAH loads well below the lethal threshold concentrations established in laboratory bioassays, and very low concentrations of HPAH compounds were present. These results indicate that petroleum hydrocarbons dissolved from oil deposits on intertidal beaches are not at concentrations that pose toxic risk to incubating pink salmon eggs. The evidence does not support the hypothesis that interstitial pore water in previously oiled beaches is highly toxic. [source] Bioaccumulation of native polycyclic aromatic hydrocarbons from sediment by a polychaete and a gastropod: Freely dissolved concentrations and activated carbon amendmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2006Gerard Cornelissen Abstract The present paper describes a study on the bioaccumulation of native polycyclic aromatic hydrocarbons (PAHs) from three harbors in Norway using the polychaete Nereis diversicolor and the gastropod Hinia reticulata. First, biota,sediment accumulation factors (BSAFs) were measured in laboratory bioassays using the original sediments. Median BSAFs were 0.004 to 0.01 kg organic carbon/kg lipid (10 PAHs and 6 organism,sediment combinations), which was a factor of 89 to 240 below the theoretical BSAF based on total sediment contents (which is approximately one). However, if BSAFs were calculated on the basis of measured freely dissolved PAH concentrations in the pore water (measured with polyoxymethylene passive samplers), it appeared that these BSAFfree values agreed well with the measured BSAFs, within a factor of 1.7 to 4.3 (median values for 10 PAHs and six organism,sediment combinations). This means that for bioaccumulation, freely dissolved pore-water concentrations appear to be a much better measure than total sediment contents. Second, we tested the effect of 2% (of sediment dry wt) activated carbon (AC) amendments on BSAF. The BSAFs were significantly reduced by a factor of six to seven for N. diversicolor in two sediments (i.e., two of six organism,sediment combinations), whereas no significant reduction was observed for H. reticulata. This implies that either site-specific evaluations of AC amendment are necessary, using several site-relevant benthic organisms, or that the physiology of H. reticulata caused artifactually high BSAF values in the presence of AC. [source] A test system to evaluate the susceptibility of Oregon, USA, native stream invertebrates to triclopyr and carbarylENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Jennifer L. Peterson Abstract The susceptibility of six indigenous macroinvertebrate species representative of U.S. Pacific Northwest streams (Ameletus sp., Brachycentrus americanus, Calineuria californica, Cinygma sp., Lepidostoma unicolor, Psychoglypha sp. early and late instar) to formulated triclopyr ester (herbicide) and carbaryl (insecticide) was determined using laboratory bioassays. Acute toxicity was expressed as the lethal concentration to 50% (LC50) and 1% (LC1) of the test population based on a 96-h exposure duration. Carbaryl was found to be 1,000 times more toxic than triclopyr for all the organisms tested. The LC1 values (7.5, 28.8, 9.0, 3.0, 9.5, 14.8, 33.8 ,g/L, respectively, for carbaryl and 1.8, 3.9, 4.0, 4.2, 29.0, 16.1 mg/L, respectively, for triclopyr) were used in the calculation of hazardous concentration to 5% of the stream macroinvertebrate community (HC5) based on the lower 95% confidence limit (HC5/95). The hazardous concentration (HC5/95) for triclopyr was 0.11 mg/L and for carbaryl ranged from 0.43 to 0.66 ,g/L, respectively. Triclopyr and carbaryl symptomology were analyzed for two organisms, C. californica and Cinygma sp. Carbaryl symptomology included knockdown and moribund states with severity and time of appearance being a function of dose. In triclopyr poisoning, death occurred suddenly with little or no symptomology. Time to 50% mortality (LT50) values were consistently higher for C. californica than for Cinygma sp. exposed to both chemicals at similar concentrations. [source] Temptations of weevil: feeding and ovipositional behaviour of Hylobius warreni Wood on host and nonhost bark in laboratory bioassaysAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2009Gareth R. Hopkins Abstract 1Warren root collar weevil Hylobius warreni Wood (Coleoptera: Curculionidae) is a long-lived, flightless insect native to coniferous forests across northern North America. Girdling by larval feeding causes significant mortality on young trees. The insect poses considerable challenges to reforestation. 2Adult weevils feed on all life stages of a variety of coniferous hosts prior to oviposition. Their relative feeding preferences, however, have not been quantified. Moreover, it is not known whether host bark influences oviposition behaviour. 3Feeding preferences of adult weevils were tested in both choice and no-choice laboratory bioassays using small branches from three conifers (lodgepole pine Pinus contorta var. latifolia, interior hybrid spruce Picea glauca×engelmannii, and Douglas-fir Pseudotsuga menziesii) and one deciduous tree (trembling aspen Populus tremuloides). Measurements included the surface area of bark consumed, rate of consumption, the number of days of feeding, and, in the no-choice assay, the number of eggs oviposited. 4Bark consumption was greatest on pine and Douglas-fir, followed by spruce. Little to no feeding occurred on aspen. Consumption did not vary between male versus female insects for any of the feeding metrics quantified. 5The presence of aspen branches did not inhibit feeding on any of the other species in the choice bioassays. 6The number of eggs laid by female insects did not differ significantly among tree species in the no-choice assay. Eggs were laid indiscriminately in the presence of all four host types. 7Results and opportunities for future research are discussed in the context of formulating new integrated pest management strategies for this insect, which is increasingly important in the period of reforestation subsequent to the mountain pine beetle epidemic in western Canada. [source] Resistance of kale varieties to attack by Mamestra brassicaeAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2009María E. Cartea Abstract 1,The objectives of this work were to study the resistance of six kale (Brassica oleracea acephala group) varieties to cabbage moth Mamestra brassicae (L.) expressed as antibiosis and to determine the effect of plant age on larval survival and development. 2,The influence of plant age on resistance was determined using leaves from seedlings and from mature plants. Survival and development of M. brassicae larvae and feeding rates were determined in laboratory bioassays. 3,Leaves from seedlings were more suitable than those of mature plants for establishing differences in resistance. There were significant differences between kale varieties in larval survival, growth rate, leaf feeding, and time to pupation but not pupal weight. The varieties MBG-BRS0031, MBG-BRS0351, and MBG-BRS0287 reduced survival of M. brassicae larvae. Larvae that fed on MBG-BRS0060 were the heaviest and took the longest time to pupation. MBG-BRS0031 was consumed significantly less by larvae than were all the other varieties examined. Leaves from mature plants of MBG-BRS0142 and MBG-BRS0170 were defoliated significantly less than those of other varieties. 4,In conclusion, the variety MBG-BRS0031 may be a promising source of resistance to M. brassicae. Leaf antibiotic resistance was shown to play a role in defense against M. brassicae attack but it is not the only possible mechanism of resistance. [source] Herbivores and pathogens on willow: do they affect each other?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2003Matthias Simon Abstract 1,Willows often need to cope with attack by both rust fungi and herbivores. We studied whether rust infection on willow affects the herbivore, and vice versa, whether herbivore feeding affects the fungal infection. The system investigated by laboratory bioassays and greenhouse experiments consisted of the willow hybrid Salix × cuspidata, the rust Melampsora allii-fragilis and the willow leaf beetle Plagiodera versicolora. Effects were studied both on a local scale (rust infection and feeding on the same leaf) and systemically (rust infection and feeding on different, but adjacent leaves). 2,Rust infection was not affected by herbivore feeding on a local scale. Systemically, however, the willow's susceptibility towards rust infection was increased by herbivore feeding, as indicated by a higher number of rust sori on leaves adjacent to feeding-damaged leaves. The herbivore's performance was detrimentally affected by rust infection: increase of mortality (systemically), decrease of larval weight (locally and systemically) and prolonging of developmental time (locally and systemically). 3,Previous rust infection enhanced systemically the willow's susceptibility towards subsequent fungal infection. Previous herbivore feeding on the willow had no effects on the herbivore's developmental time and mortality. However, feeding upon previously feeding-damaged willow leaves significantly reduced larval weight. [source] Role of bacteria in the oviposition behaviour and larval development of stable fliesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2006A. Romero Abstract., Stable flies, Stomoxys calcitrans (L.), are the most important pests of cattle in the United States. However, adequate management strategies for stable flies, especially for pastured cattle, are lacking. Microbial/symbiont-based approaches offer novel venues for management of insect pests and/or vector-borne human and animal pathogens. Unfortunately, the fundamental knowledge of stable fly,microbial associations and their effect on stable fly biology is lacking. In this study, stable flies laid greater numbers of eggs on a substrate with an active microbial community (> 95% of total eggs oviposited) than on a sterilized substrate. In addition, stable fly larvae could not develop in a sterilized natural or artificial substrate/medium. Bacteria were isolated and identified from a natural stable fly oviposition/developmental habitat and their individual effect on stable fly oviposition response and larval development was evaluated in laboratory bioassays. Of nine bacterial strains evaluated in the oviposition bioassays, Citrobacter freundii stimulated oviposition to the greatest extent. C. freundii also sustained stable fly development, but to a lesser degree than Serratia fanticola. Serratia marcescens and Aeromonas spp. neither stimulated oviposition nor supported stable fly development. These results demonstrate a stable fly bacterial symbiosis; stable fly larval development depends on a live microbial community in the natural habitat, and stable fly females are capable of selecting an oviposition site based on the microbially derived stimuli that indicate the suitability of the substrate for larval development. This study shows a promising starting point for exploiting stable fly,bacterial associations for development of novel approaches for stable fly management. [source] Responses of Corcyra cephalonica (Stainton) to pirimiphos-methyl, spinosad, and combinations of pirimiphos-methyl and synergized pyrethrins,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2004Fangneng Huang Abstract Field control failures with pirimiphos-methyl against the rice moth, Corcyra cephalonica (Stainton), in Weslaco, Texas, USA, led us to investigate the susceptibility of this particular strain to pirimiphos-methyl, spinosad, pyrethrins synergized with piperonyl butoxide, and pirimiphos-methyl combined with synergized pyrethrins. In laboratory bioassays, 50 eggs of C cephalonica were exposed to untreated and insecticide-treated corn and sunflower seeds to determine larval survival after 21 days, egg-to-adult emergence after 49 days, and larval damage to seeds at both exposure periods. Pirimiphos-methyl at both 4 and 8 mg kg,1 did not prevent larval survival or egg-to-adult emergence of C cephalonica on either corn or sunflower seeds, and seed damage was evident at both rates. The C cephalonica strain was highly susceptible to spinosad at 0.5 and 1 mg kg,1. At both spinosad rates, reduction in larval survival, egg-to-adult emergence, and seed damage relative to the control treatment was ,93% on both corn and sunflower seeds. Pirimiphos-methyl and spinosad were generally more effective against C cephalonica on corn than sunflower seeds. The C cephalonica strain was completely controlled on corn treated with 1.5 mg kg,1 of pyrethrins synergized with 15 mg kg,1 of piperonyl butoxide. Many larvae survived and became adults on corn treated with synergized pyrethrins at ,0.75 mg kg,1. Corn treated with pirimiphos-methyl at 4, 6 or 8 mg kg,1 in combination with 0.38 to 1.5 mg kg,1 of synergized pyrethrins reduced larval survival by ,95%, egg-to-adult emergence by ,97%, and seed damage by ,94%. Our results suggest that the C cephalonica strain can be controlled on corn by combining pirimiphos-methyl with synergized pyrethrins or with synergized pyrethrins at the labeled rate. Although spinosad is not currently labeled for use on stored corn and sunflower seeds, it appears to be effective against C cephalonica on both commodities at very low rates. Copyright © 2004 Society of Chemical Industry [source] Effect of the combined treatment of insecticides and an attractant for the control of Phloeotribus scarabaeoides, a pest of Olea europeaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2003Estefanía Rodríguez Abstract Different insecticides have been tested for the control of the olive bark beetle, Phloeotribus scarabaeoides Bern. This scolytid can be managed at two points in its biological cycle: in pruned logs, where it excavates reproduction galleries, or in living trees, after emergence from the logs, where it digs feeding galleries. In mortality laboratory bioassays, the efficiency of organophosphorus insecticides has been ranked as follows: chlorpyrifos,+,dimethoate,<,formothion,<,methidathion. Formothion and methidathion, the two most efficient, were sprayed on olive logs together with a pyrethroid insecticide, deltamethrin, and a formulation which combined an organophosphorus (fenitrothion) and a pyrethroid (cypermethrin) insecticide. Deltamethrin inhibited the excavation of new reproduction galleries and induced a repellent effect on the olive pest. In contrast, none of the organophosphorus insecticides or the combination, fenitrothion,+,cypermethrin, were able to control the olive bark beetle. In olive trees, deltamethrin controlled this olive pest without showing the repellent effect observed for logs. Ethylene, a plant hormone, has been reported as an attractant for the olive bark beetle. The use of dispensers which released ethylene increased the number of P scarabaeoides approaching the treated olive trees, thus favouring its use in a lure-and-trap control system. © 2003 Society of Chemical Industry [source] Speed of action and in vitro efficacy of spinosad against sheep body lice, Bovicola ovis (Schrank) (Phthiraptera: Trichodectidae), resistant to pyrethroid, organophosphate or insect growth regulator insecticidesAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2008Garry Levot Abstract, Results of laboratory bioassays indicated that spinosad was equally effective against sheep lice populations that were susceptible to insecticides or resistant to pyrethroid, organophosphorus or insect growth regulator (IGR) insecticides. Spinosad had similar toxicity against susceptible strains of lice to that previously reported for diazinon, but lower toxicity than cypermethrin. Lethal concentrations of spinosad and diazinon caused knock down of lice within 6 h of exposure and death within 24 h. Prior to the current phasing out of diazinon as a sheep dip, most wool producers, needing to control pyrethroid- or IGR-resistant lice infestations in short-wool, would have chosen to use diazinon. Our results suggest that spinosad is an effective alternative for treatment of lice resistant to other chemical groups. [source] | ||||||||||