Insecticides Lambda-cyhalothrin Research Articles

Potential for Integrated Management of Soybean Virus Disease.

The recent introduction of the colonizing soybean aphid (Aphis glycines) to soybean in the northern United States has raised concern for potential increased disease caused by the nonpersistently aphid-transmitted Soybean mosaic virus (SMV). This study was conducted to examine the potential integration of host plant resistance and insecticide tactics for control of virus disease. Research from four location-years demonstrated that foliar application of the pyrethroid insecticide lambda-cyhalothrin (Warrior) or the organophosphate chlorpyrifos (Lorsban 4E) timed to suppress soybean aphid populations does not reduce SMV. Therefore, the introduction of a colonizing aphid to the array of migratory noncolonizing aphids that transmit SMV does not result in potential for disease control through vector suppression by foliar insecticides. Treatment also did not result in management of Bean pod mottle virus (BPMV), transmitted by the bean leaf beetle (Cerotoma trifurcata), presumably because of issues related to different phenologies of the insect vectors. Soybean cultivars with the lowest virus titer in seed produced the highest grain yield and, thus, were rated as field tolerant compared with cultivars with the highest virus titer in seed. Host plant resistance, not vector control, is the most effective tactic to control SMV.

Effects of lambda-cyhalothrin and Beauveria bassiana spores on abundance of Chilean soil surface predators, especially spiders and carabid beetles

Summary The effects on generalist predators of the insecticide lambda-cyhalothrin and a new biopesticide based on Beauveria bassiana spores were studied in the 2003 growing season (October to December, Southern spring) in Valdivia, Chile. Both pesticides target larvae of Dalaca spp. (Lepidoptera: Hepialidae), a complex formed by Dalaca chiliensis, Dalaca pallens and Dalaca variabilis. Lambda-cyhalothrin, B. bassiana spores and water (control) were sprayed once. Pitfall traps were used to sample predators one day before spraying as well as 1, 30 and 60 days after spraying. Sampling revealed an assemblage of 11 carabid species and two spider families (Lycosidae and Gnaphosidae). In order of abundance, the carabid species found were Ferionomorpha nebroides (45%), Allendia chilensis (20%), Argutoridius chilensis (13%), Ferionomorpha aerea (11%) and Ceroglossus chilensis (6%). Metius flavipes, Mimodromites cyaneus, Parhypates sp., Trechisibus angularis, Calosoma vagans and Trirammatus unistriatus accounted for less than 1% each. Spider families were almost equally represented. Activity of predators increased over time and negative effects of lambda-cyhalothrin were detected for F. nebroides, F. aerea, Lycosidae and Gnaphosidae. Differences vanished by day 60, except for F. aerea. Inundative release of B. bassiana spores affected only F. aerea at the last sampling date. Therefore, B. bassiana isolate B-931 is a good potential alternative to the broad-spectrum insecticide lambda-cyhalothrin, which disrupted the generalist predator assemblage more severely.

Effects of Reduced Rates of Two Insecticides on Enzyme Activity and Mortality of an Aphid and Its Lacewing Predator

By applying insecticides at lower rates of active ingredients per unit area, survival rates of the pests' natural enemies can be enhanced, whereas pest mortality can remain high. The effects of reduced application rates of the insecticides lambda-cyhalothrin and dimethoate on the mortality of bird cherry-oat aphid, Rhopalosiphon padi (L.), and lacewing Micromus tasmaniae Walker were determined in the laboratory and field. Cholinesterase (ChE) and glutathione S-transferase (GST) activities in survivors provided a measure of sublethal effects and general fitness. In the laboratory, lacewings were less sensitive than aphids to both insecticides, and dimethoate was more toxic than lambda-cyhalothrin. However, these results could not be recreated in the field, in part due to very low recapture rates. In summary, lambda-cyhalothrin seemed to have no effect on aphids, but it was toxic to lacewings. Dimethoate was far less toxic in the field, but aphids were still more sensitive than were lacewings. Cholinesterase activity was reduced by dimethoate exposure in the laboratory in both species, but there were species-specific differences. Dimethoate and lambda-cyhalothrin had no effects on GST activity in either species. The high mortality rate for lacewings and aphids exposed to dimethoate in the field suggests that the application rate could be reduced to as low as 10% of that recommended by manufacturers, and this should still be highly efficacious against aphids, while protecting the predatory lacewing. Measurement of enzyme activity could provide a useful indicator of "fitness" of survivors.

Separation and Aquatic Toxicity of Enantiomers of the Pyrethroid Insecticide Lambda-Cyhalothrin

Separation and Aquatic Toxicity of Enantiomers of the Pyrethroid Insecticide Lambda-Cyhalothrin

Microbiological characteristics of a sandy loam soil exposed to tebuconazole and λ-cyhalothrin under laboratory conditions

Changes in microbiological properties of a sandy loam soil in response to the addition of different concentrations of fungicide tebuconazole and pyrethroid insecticide lambda-cyhalothrin were assessed under laboratory conditions. To ascertain these changes, the potentially active soil microbial biomass, concentrations of ammonium and nitrate ions, numbers of total culturable bacteria, fungi, nitrogen-fixing bacteria, nitrifying and denitrifying bacteria were determined. Substrate-induced respiration (SIR) increased with time in both control (ranged from 13.7 to 23.7 mg/O(2)/kg(-1)/dry soil/h(-1)) and pesticide treated soil portions. For both pesticides, SIR values ranged from 12-13 to 23-25 mg/O(2)/kg(-1)/dry soil/h(-1) on days 1 and 28, respectively. Also, concentrations of nitrate and ammonium ions, numbers of total culturable bacteria, denitrifying bacteria, nitrogen-fixing bacteria (for the insecticide) and fungi (for the insecticide) were either unaffected or even stimulated by the pesticide treatments. The adverse impacts of the pesticides were observed for nitrate concentrations (on days 1 or 7), numbers of nitrifying bacteria (on day 1), denitrifying bacteria (for the insecticide on days 1 and 14), nitrogen-fixing bacteria (for tebuconazole on day 1) as well as numbers of fungi in tebuconazole-treated soil (on days 1 and 14).

Response of grassland soil arthropod community to biological and conventional control of a native moth: using Beauveria bassiana and lambda-cyhalothrin for Dalaca pallens (Lepidoptera: Hepialidae) suppression

Conventional and biological control of a native moth, Dalaca pallens (Blanchard) (Lepidoptera: Hepialidae), were evaluated in Southern Chile in relation to changes on community metrics (diversity, species richness, evenness and dominance) of a soil-dwelling invertebrate assemblage. Two experiments were conducted (in winter and spring) to compare non-target effects of Beauveria bassiana (Balsamo) Vuillemin and lambda-cyhalothrin insecticide. The invertebrate community was sampled before and after spraying by extracting soil cores. Estimates of diversity (Shannon index), species richness, evenness (Hurlbert’s Probability of Interspecific Encounter) and dominance indicated that the invertebrate assemblage was strongly disturbed by lambda-cyhalothrin treatment but not by B. bassiana applied in winter, over the sampling period (40 days). Spring results revealed that diversity and evenness at control and at B. bassiana plots were similar between them and higher than at lambda-cyhalothrin plots, while there were no differences between sites 30 days after treatment in species richness. Inundative biological control using B. bassiana strain QU-B931 was considered to pose lower ecological risk than lambda-cyhalothrin, currently one of the most frequently used insecticides for D. pallens control.

Effects of carbendazim and lambda-cyhalothrin on soil invertebrates and leaf litter decomposition in semi-field and field tests under tropical conditions (Amazônia, Brazil)

Effects of the fungicide carbendazim and of the insecticide lambda-cyhalothrin on soil invertebrates and litter decomposition under tropical conditions were assessed in ecotoxicological semi-field studies using intact soil-core terrestrial model ecosystems (TMEs) and in a field test applying the litter-bag method. In the TME study, performed indoors under controlled conditions, earthworms, isopods and diplopods were added to intact soil cores and mortality of soil invertebrates and mass loss of leaf litter were assessed. The field study was performed on an abandoned rubber plantation near Manaus (Amazonia, Brazil). The measurement endpoints were abundance of the soil fauna and mass loss of leaf litter. In the TMEs carbendazim caused a decrease in the abundance of the introduced earthworm Pontoscolex corethrurus and, partly, of the milliped Trigoniulus corallinus. In the field carbendazim decreased the abundance of the native earthworm Andiorrhinus amazonius. Lambda-cyhalothrin was toxic to isopods and millipedes in the TMEs, whereas no effect on arthropods was detected in the field. Organic matter breakdown measured as mass loss of leaf litter in TMEs over time revealed that the two tested agrochemicals can have an impact on decomposition at field relevant concentrations. In the field the results were less obvious, due to spatial heterogeneity through which possible effects of the tested agrochemicals could have been masked.

Susceptibilidade de lagartas dos biótipos milho e arroz de Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) a inseticidas com diferentes modos de ação

O objetivo do trabalho foi avaliar a susceptibilidade de lagartas dos biótipos milho e arroz de Spodoptera frugiperda, a inseticidas com diferentes modos de ação. Os insetos foram coletados em milho e em arroz irrigado no agroecossistema de várzea, município de Pelotas, região que produz milho e arroz irrigado (lado a lado). Os experimentos foram realizados, em condições controladas de temperatura (25 ± 1°C), umidade relativa (70 ± 10%) e fotofase (14 horas), utilizando-se folhas do híbrido de milho Pionner 30F33 (40 dias após a emergência). As folhas pulverizadas em torre de Potter calibrada para aplicação de um volume de calda de 1,7 ± 0,305mg cm-2, foram colocadas em recipientes de plásticos com tampa, sendo individualizadas 25 lagartas de 3° ínstar de cada biótipo de S. frugiperda. Os inseticidas e concentrações avaliados foram: clorpirifós [Lorsban 480 BR, 0,960g i.a. L-1 (Organofosforado)], lambda-cialotrina [Karate Zeon 50 CE, 0,003g i.a. L-1 (Piretróide sintético)], lufenuron [Match CE, 0,006g i.a. L-1 (Aciluréia)], methoxifenozide [Intrepid 240 SC, 0,158g i.a. L-1 (Diacilhidrazina)] e spinosad [Tracer, 0,960g i.a. L-1 (Naturalyte)]. A avaliação da mortalidade foi realizada 24, 48, 72, 96 e 120 horas após o tratamento. O biótipo milho de S. frugiperda foi menos suscetível aos inseticidas lambda-cialotrina, lufenuron e methoxifenozide. Os inseticidas clorpirifós e spinosad foram eficientes no controle das lagartas dos biótipos milho e arroz de S. frugiperda.

Ecological Effects of Spring and Late Summer Applications of Lambda-Cyhalothrin on Freshwater Microcosms

The aim of the study was to compare the effects of the pyrethroid insecticide lambda-cyhalothrin (treated at 10, 25, 50, 100, 250 ng active ingredient a.i./L) on a drainage ditch ecosystem in spring and late summer. Microcosms (water volume approximately 430 L) were established using enclosures in a 50-cm-deep experimental ditch system containing communities typical of macrophyte-dominated freshwater ecosystems. Effects on macroinvertebrates, zooplankton, phytoplankton, macrophytes, and community metabolism were assessed and evaluated using univariate and multivariate statistical techniques. The macroinvertebrate community responded most clearly to treatment and, as anticipated, insects and crustaceans were among the most sensitive organisms. Statistical analysis showed that the underlying community structure was significantly different between the spring and summer experiments. However, the most sensitive species (Chaoborus obscuripes and Gammarus pulex) were abundant in spring as well as in late summer. In spring and late summer, only slight and transient effects were observed at the community level in the 10-ng/L treatment. Overall, the study did not show substantial differences in the responses of sensitive taxa between spring and late summer treatments, and effects thresholds were similar irrespective of season of treatment.

Interactions of Late-Season Morningglory (Ipomoea spp.) Management Practices in Peanut (Arachis hypogaea)1

Experiments were conducted in North Carolina during 2002 and 2003 to evaluate entireleaf morningglory control by 2,4-DB applied alone or with seven fungicides. In a separate group of experiments, tall morningglory control by 2,4-DB was evaluated when applied in four-way mixtures with the following: the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, or tebuconazole; the insecticide lambda-cyhalothrin; and the foliar fertilizer disodium octaborate or the plant growth regulator (PGR) prohexadione calcium plus urea ammonium nitrate. Pyraclostrobin, but not azoxystrobin, boscalid, chlorothalonil, fluazinam, propiconazole plus trifloxystrobin, or tebuconazole, reduced entireleaf morningglory control by 2,4-DB. Mixtures of fungicides, insecticides, and foliar fertilizer/ PGR did not affect tall morningglory control by 2,4-DB. Placing artificial morningglory in the peanut canopy when fungicides were applied did not intercept enough fungicide to increase peanut defoliation by early leaf spot and web blotch or reduce pod yield compared with fungicide applied without artificial morningglory.Nomenclature: 2,4-DB; azoxystrobin; boscalid; chlorothalonil; fluazinam; lambda-cyhalothrin; prohexadione calcium; propiconazole; pyraclostrobin; tebuconazole; trifloxystrobin; entireleaf morningglory, Ipomoea hederacaea var integriuscula Gray #3 IPOHG; tall morningglory, Ipomoea purpurea (L.) Roth # PHBPU; early leaf spot, Cercospora arachidicola S. Hori; web blotch, Phoma arachidicola (Marsas et al.); peanut, Arachis hypogaea L. ‘NC-V 11’, ‘VA 98R’.Additional index words: Fungicide deposition, pesticide interactions, weed interference.Abbreviations: PGR, plant growth regulator; UAN, urea ammonium nitrate.

Glyphosate Efficacy on Selected Weed Species Is Unaffected by Chemical Coapplication1

A study was conducted in 2004 to determine the effect of coapplication of the insecticides acephate, acetamiprid, bifenthrin, cyfluthrin, cypermethrin, dicrotophos, dimethoate, emanectin benzoate, imidacloprid, indoxacarb, lambda-cyhalothrin, methoxyfenozide, spinosad, thiamethoxam, and zeta-cypermethrin; the plant growth-regulator mepiquat pentaborate; a foliar sodium calcium borate micronutrient solution; and a foliar nitrogen fertilizer solution with glyphosate on the efficacy of weeds that commonly infest cotton. Barnyardgrass, hemp sesbania, johnsongrass, pitted morningglory, and sicklepod were grown in outdoor containers and treated with glyphosate at 1,120 g ai/ha alone or in coapplication at the three-to four- or seven-to eight-leaf growth stage. Glyphosate efficacy, based on visual control ratings at 7, 14, and 28 d after treatment (DAT) and fresh weight reduction of weed biomass at 28 DAT, was unaffected by chemical coapplication or application timing. Averaged across application timing and visu...

Stream macroinvertebrate drift response to pulsed exposure of the synthetic pyrethroid lambda‐cyhalothrin

Outdoor experimental channels were used to study the behavioral changes of stream macroinvertebrates exposed to a pulse of the pyrethroid insecticide lambda-cyhalothrin. The primary end point was the number of macroinvertebrates drifting, but the mobility of macroinvertebrates caught in the drift also was assessed. A specified number of two insect species, Baetis rhodani and Leuctra fusca/digitata, and of the amphipod Gammarus pulex were introduced into small replicated subsections of the experimental channels. Macroinvertebrates were allowed to acclimatize for 26 h prior to a 60-min pulsed exposure to lambda-cyhalothrin. Measurement was initiated 2 h before pesticide application and continued for the following 24 h. Pulse concentrations of lambda-cyhalothrin of 0.001, 0.01, 0.1, and 1.0 microg L(-1) were applied, and each experiment was replicated 8 times. All three species responded to the pesticide pulse with catastrophic drift. The 0.001 microg L(-1) treatment caused a significant increase in the drift of Gammarus, whereas the drift response threshold was 0.01 microg L(-1) for the two insect species. Drift response onset followed the applied pulse concentration, with the highest concentrations resulting in more individuals of all species entering drift at an early stage. The majority of individuals caught in drift samples during low concentrations showed no change in mobility. At the two highest concentrations, however, both Baetis and Leuctra were in the process of being immobilized, with Leuctra the more sensitive of the two. In contrast, only a few of the Gammarus individuals caught showed changes in mobility after the high-concentration treatments. The present study shows that lambda-cyhalothrin is a potential hazard for macroinvertebrate populations in headwater streams. The clear species-specific responses indicate that sublethal doses have the potential to change the macroinvertebrate community structure.

Trifloxysulfuron–Insecticide Combination Effects on Broadleaf Weed and Thrips (Frankliniella spp.) Control in Cotton

Coapplication of herbicides and insecticides affords growers an opportunity to control multiple pests with one application given that efficacy is not compromised. Trifloxysulfuron was applied at 5.3 g ai/ha both alone and in combination with the insecticides acephate (370 g ai/ha), oxamyl (370 g ai/ha), lambda-cyhalothrin (34 g ai/ha), acetamiprid (45 g ai/ha), thiamethoxam (45 g ai/ha), endosulfan (379 g ai/ha), indoxacarb (123 g ai/ha), emamectin benzoate (11 g ai/ha), methoxyfenozide (67 g ai/ha), spinosad (75 g ai/ha), and pyridalyl (112 g ai/ha) to determine the effects of coapplication on control of some of the more common and/or troublesome broadleaf weeds infesting cotton. In addition, the insecticides acephate, oxamyl, lambda-cyhalothrin, thiamethoxam, and endosulfan, at the rates listed above, were applied either alone or in combination with trifloxysulfuron at 7.9 g/ha to assess the effects of coapplication on thrips control. Control of hemp sesbania (insecticides oxamyl and lambda-cyhalothrin), sicklepod (insecticides methoxyfenozide and pyridalyl), redroot pigweed (insecticides thiamethoxam, methoxyfenozide, spinosad, and pyridalyl), and smooth pigweed, Palmer amaranth, and common lambsquarters (all insecticides) with trifloxysulfuron may be reduced when coapplied with the indicated insecticides for each species. Control of pitted, tall, ivyleaf, and entireleaf morningglory with trifloxysulfuron was not affected by the insecticides evaluated. Coapplication of trifloxysulfuron with the insecticides evaluated also resulted in no negative effects on thrips control.

Control of Selected Broadleaf Weeds with Glufosinate as Influenced by Insecticide Coapplication

Coapplication of herbicides and insecticides affords growers an opportunity to control multiple pests with one application, given that efficacy is not compromised. Glufosinate was applied at 470 g ai/ha both alone and in combination with the insecticides acephate, acetamiprid, bifenthrin, cyfluthrin, dicrotophos, emamectin benzoate, imidacloprid, indoxacarb, lambda-cyhalothrin, methoxyfenozide, spinosad, or thiamethoxam to determine coapplication effects on control of some of the more common and/or troublesome broadleaf weeds infesting cotton. Hemp sesbania, pitted morningglory, prickly sida, redroot pigweed, and sicklepod were treated at the three- to four- or the seven- to eight-leaf growth stage. When applied at the earlier application timing, glufosinate applied alone provided complete control at 14 d after treatment, and control was unaffected by coapplication with insecticides. When glufosinate application was delayed to the later application timing, visual weed control was unaffected by insecticide coapplication. Fresh-weight reduction from the herbicide applied to larger weeds was negatively impacted by addition of the insecticides dicrotophos and imidacloprid with respect to redroot pigweed and prickly sida, but only in one of two experiments. In most cases, delaying application of glufosinate to larger weeds resulted in reduced control compared to that from a three- to four-leaf application, with the extent of reduction varying by species. Results indicate that when applied according to the herbicide label (three- to four-leaf stage), glufosinate/ insecticide coapplications offer producers the ability to integrate pest management strategies and to limit application costs without sacrificing control of the broadleaf weeds evaluated.

Insecticide drift deposition on noncrop plant surfaces and its impact on two beneficial nontarget arthropods, aphidius colemani viereck (hymenoptera, braconidae) and coccinella septempunctata L. (coleoptera, coccinellidae)

Drift of the pyrethroid insecticide lambda-cyhalothrin into field margins bordering wheat and its effect on nontarget arthropods was investigated under field conditions. Insecticide deposition on leaf surfaces of broad beans exposed within field margins at 1-, 2-, and 3-m distance from the field edge and directly within the crop was quantified using a fluorescent tracer. The toxicity of leaf deposits to the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae) and to larvae of the ladybird Coccinella septempunctata L. (Coleoptera: Coccinellidae) was estimated. Mean corrected mortalities of A. colemani were < 50% (1 m) and < 30% (2 and 3 m), and mortalities of C. septempunctata larvae were < or = 80% (1 m), < or = 67% (2 m), and < or = 52% (3 m) 12 and 24 h postexposure to drift deposits. High positive correlation coefficients proved the relationship between leaf deposits and mortalities of test organisms. The connection of drift deposit measurement and exposure bioassay provides a promising approach to determining effects of insecticide drift on nontarget arthropods. However, due to the patchiness of drift deposition on noncrop plant surfaces, risks to nontarget arthropods at defined distances from the sprayed crop are not highly predictable.

Effects of lambda‐cyhalothrln in two ditch microcosm systems of different trophic status

The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (approximately 0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L. The rate of dissipation of lambda-cyhalothrin in the water column of the two types of test systems was similar. After 1 d, only 30% of the amount applied remained in the water phase. Initial, direct effects were observed primarily on arthropod taxa. The most sensitive species was the phantom midge (Chaoborus obscuripes). Threshold levels for slight and transient direct toxic effects were similar (10 ng/L) between types of test systems. At treatment levels of 25 ng/L and higher, apparent population and community responses occurred. At treatments of 100 and 250 ng/L, the rate of recovery of the macroinvertebrate community was lower in the macrophyte-dominated systems, primarily because of a prolonged decline of the amphipod Gammarus pulex. This species occurred at high densities only in the macrophyte-dominated enclosures. Indirect effects (e.g., increase of rotifers and microcrustaceans) were more pronounced in the plankton-dominated test systems, particularly at treatment levels of 25 ng/L and higher.

Sicklepod (Senna obtusifolia) Control and Seed Production after 2,4-DB Applied Alone and with Fungicides or Insecticides

Experiments were conducted during 1999, 2002, and 2003 to evaluate sicklepod control by 2,4-DB applied alone or in mixture with selected fungicides and insecticides registered for use in peanut. The fungicides boscalid, chlorothalonil, fluazinam, propiconazole plus trifloxystrobin, pyraclostrobin, or tebuconazole and the insecticides acephate, carbaryl, esfenvalerate, fenpropathrin, lambda-cyhalothrin, methomyl, or indoxacarb applied in mixtures with 2,4-DB did not reduce sicklepod control by 2,4-DB compared with 2,4-DB alone. The fungicide azoxystrobin reduced control in some but not all experiments. Sicklepod control was highest when 2,4-DB was applied before flowering regardless of fungicide treatment. Seed production and germination were reduced when 2,4-DB was applied 81 to 85 d after emergence when sicklepod was flowering. Applying 2,4-DB before flowering and at pod set and pod fill did not affect seed production.

Terrestrische ökotoxikologische Testmethoden für die Tropen

Goal, Scope, and BackgroundSoil organisms play a crucial role in the terrestrial ecosystem. Plant Protection Products (PPPs) are known to affect soil organisms and might have negative impacts on soil functions influenced by these organisms. Little research has been done to day on the impact of PPs on tropical ecosystems. Therefore, in this study it was investigated whether fate and effects of pesticides differ between tropical and temperate regions and whether data generated under temperate conditions can be used for the Environmental Risk Assessment (ERA) in tropical regions.MethodsIn the first part of this study, the effects of two fungicides (Benomyl and Carbendazim) and one insecticide (lambda-Cyhalothrin) on soil invertebrates (i.e. earthworms and arthropods) were evaluated in laboratory tests modified for tropical conditions (temperature, soil, test species). Besides using some native species, the tests were done mainly with two (temperate and tropical) strains of earthworms (Eisenia fetida) and the peregrine isopod speciesPorcellionides pruinosus as standard test species. The chemicals were spiked in two natural and two artificial soils. A tropical artificial soil (TAS), containing a tropical fern product (Xaxim) or coconut coir dust as organic matter, was developed in this study.Results and ConclusionsThe results from the laboratory tests showed that all three test chemicals differed from those gained under temperate conditions. In the case of the fungicides the toxicity was lower but in the case of the insecticide higher under tropical than under temperate conditions. The native tropical earthwormPontoscolex corethrurus reacted more sensitively against Carbendazim in comparison to the standard test speciesEisenia fetida.Recommendation and PerspectiveDetails of the environmental risk assessment of the three model chemicals based on the results of the laboratory described here (and including the results of higher tier tests (semi-field and field tests)) will be described in Part 2 of this series

Aquatic risk assessment of a realistic exposure to pesticides used in bulb crops: a microcosm study.

The fungicide fluazinam, the insecticide lambda-cyhalothrin, and the herbicides asulam and metamitron were applied to indoor freshwater microcosms (water volume approximately 0.6 m3). The treatment regime was based on a realistic application scenario in tulip cultivation. Concentrations of each pesticide were equal to 0%, 0.2%, 0.5%, 2%, and 5% spray drift emission of label-recommended rates. Contribution of compounds to the toxicity of the pesticide package was established by expressing their concentrations as fractions of toxic units. The fate of the compounds in the water, and responses of phytoplankton, zooplankton, periphyton, macroinvertebrates, macrophytes, decomposition, and water quality were followed for 13 weeks. The half-lives of lambda-cyhalothrin, metamitron, and fluazinam were 1 to 2 d; that of asulam was >30 d. No consistent effects could be demonstrated for the 0.2% treatment regime that was therefore considered the no-observed-effect concentration community (NOEC). The macroinvertebrate populations of Gammarus pulex, Asellus aquaticus, and Proasellus meridianus were the most sensitive end points, followed by species of copepods and cladocerans. Responses mainly were due to lambda-cyhalothrin. The 0.5% treatment regime resulted in short-term effects. Pronounced effects were observed at the 2% and 5% treatment levels. At the end of the experiment, the macrophyte biomass that consisted of Elodea nuttallii, showed a decline at the two highest treatment levels, asulam being the causal factor (NOEC: 0.5% treatment level). Primary production was reduced at the 5% treatment level only. In our experiment, the first-tier risk assessment procedure for individual compounds was adequate for protecting sensitive populations exposed to realistic combinations of pesticides. Spray drift reduction measures seem to be efficient in protecting aquatic ecosystems in agricultural areas.

Comparison of laboratory single species and field population-level effects of the pyrethroid insecticide lambda-cyhalothrin on freshwater invertebrates.

The toxicity of the pyrethroid insecticide lambda-cyhalothrin to freshwater invertebrates has been investigated using data from short-term laboratory toxicity tests and in situ bioassays and population-level effects in field microcosms. In laboratory tests, patterns of toxicity were consistent with previous data on pyrethroids. The midge Chaoborus obscuripes was most sensitive (48- and 96-h EC50 = 2.8 ng/L). Other insect larvae (Hemiptera, Ephemeroptera) and macrocrustacea (Amphipoda, Isopoda) were also relatively sensitive, with 48- and 96-h EC50 values between 10 and 100 ng/L. Generally, microcrustacea (Cladocera, Copepoda) and larvae of certain insect groups (Odonata and Chironomidae) were less sensitive, with 48-h EC50 values higher than 100 ng/L. Mollusca and Plathelminthes were insensitive and were unaffected at concentrations at and above the water solubility (5 microg/L). Generally, the EC50 values based on initial population responses in field enclosures were similar to values derived from laboratory tests with the same taxa. Also, the corresponding fifth and tenth percentile hazard concentrations (HC5 and HC10) were similar (laboratory HC5 = 2.7 ng/L and field HC5 = 4.1 ng/L; laboratory and field HC10 = 5.1 ng/L), at least when based on the same sensitive taxonomic groups (insects and crustaceans) and when a similar concentration range was taken into account. In the three field enclosure experiments and at a treatment level of 10 ng/L, consistent effects were observed for only one population (Chaoborus obscuripes), with recovery taking place within 3 to 6 weeks. The laboratory HC5 (2.7 ng/L) and HC10 (5.1 ng/L) based on acute EC50 values of all aquatic arthropod taxa were both lower than this 10 ng/L, a concentration that might represent the "regulatory acceptable concentration." The HC5 and HC10 values in this study in The Netherlands (based on static laboratory tests with freshwater arthropods) were very similar to those derived from a previous study in the United Kingdom (1.4 and 3.3 ng/L). This suggests that for pesticides like lambda-cyhalothrin, HC5 values based on static laboratory tests may provide a conservative estimate of the potential for community-level effects under field conditions. While these HC5 values are conservative for initial effects, they do not provide information on recovery potential, which may be important for regulatory decision-making.