Application Of Lambda-cyhalothrin Research Articles

Assessing the impact of coexposure on the measurement of biomarkers of exposure to the pyrethroid lambda-cyhalothrin in agricultural workers.

There are few published data on the impact of combined exposure to multiple pesticides (coexposure) on levels of biomarkers of exposure in workers, which may alter their toxicokinetics and thus the interpretation of biomonitoring data. This study aimed to assess the impact of coexposure to two pesticides with shared metabolism pathways on levels of biomarkers of exposure to pyrethroid pesticides in agricultural workers. The pyrethroid lambda-cyhalothrin (LCT) and the fungicide captan were used as sentinel pesticides, since they are widely sprayed concomitantly in agricultural crops. Eighty-seven (87) workers assigned to different tasks (application, weeding, picking) were recruited. The recruited workers provided two-consecutive 24-h urine collections following an episode of lambda-cyhalothrin application alone or in combination with captan or following tasks in the treated fields, as well as a control collection. Concentrations of lambda-cyhalothrin metabolites - 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethyl-cyclopropanecarboxylic acid (CFMP) and 3-phenoxybenzoic acid (3-PBA) - were measured in the samples. Potential determinants of exposure established in a previous study, including the task performed and personal factors were documented by questionnaire. Multivariate analyses showed that coexposure did not have a statistically significant effect on the observed urinary levels of 3-PBA (Exp(β) (95% confidence interval (95% CI)): 0.94 (0.78-1.13)) and CFMP (1.10 (0.93-1.30). The repeated biological measurements ("time variable") - defined as the within-subjects variable - was a significant predictor of observed biological levels of 3-PBA and CFMP; the within-subjects variance (Exp(β) (95% (95% CI)) for 3-PBA and CFMP was 1.11 (1.09-3.49) and 1.25 (1.20-1.31). Only the main occupational task was associated with urinary levels of 3-PBA and CFMP. Compared to the weeding or picking task, the pesticide application task was associated with higher urinary 3-PBA and CFMP concentrations. In sum, coexposure to agricultural pesticides in the strawberry fields did not increase pyrethroid biomarker concentrations at the exposure levels observed in the studied workers. The study also confirmed previous data suggesting that applicators were more exposed than workers assigned to field tasks such as weeding and picking.

Foliar application of lambda-cyhalothrin modulates root exudate profile and the rhizosphere bacteria community of dioecious Populus cathayana

Dioecious plants show sexual differences in resistance traits to abiotic stresses. However, the effects of exogenous pesticide application on female and male plant growth and their associated adaptation mechanisms are unclear. Our study investigated the effects of the broad-spectrum pesticide lambda-cyhalothrin (λ-CY) on dioecious Populus cathayana growth and explored the factors through which λ-CY changed the rhizosphere bacterial community and physicochemical soil properties via sex-specific metabolomics. The sequential application of λ-CY significantly suppressed male shoot- and root biomass, with little effect on the growth of females. Females possessed a higher intrinsic chemo-diversity within their root exudates, and their levels of various metabolites (sugars, fatty acids, and small organic acids) increased after exposure to λ-CY with consequences on bacterial community composition. Maintaining high bacterial alpha diversity and recruiting specific bacterial groups slowed down the loss of rhizosphere nutrients in females. In contrast, the reduction in bacterial alpha diversity and network structure stability in males was associated with lower rhizosphere nutrient availability. Spearman's correlation analysis revealed that several bacterial groups were positively correlated with the root secretion of lipids and organic acids, suggesting that these metabolites can affect the soil bacterial groups actively involved in the nutrient pool. This study provided novel insights that root exudates and soil microbial interactions may mediate sex-specific differences in response to pesticide application.

Effect of Insecticide Application Rates on Population Density of Orseolia oryzivora in Relation to its Parasitoids on Rice

Africa rice gall midge (Orseolia oryzivora) is a major insect pest of rice and the use of insecticides in its control poses danger to the environment and destroys biodiversity. The experiment was conducted to evaluate effect of lambda-cyhalothrin and carbofuran rates on population density of O. oryzivora in relation to its parasitoids on rice. The treatments were arranged in split-plot and fitted in to Randomized Complete Block Design, replicated three times. Observations were made on tiller number per hill, plant height, days to 50% flowering, % incidence, % severity, % parasitism of O. oryzivora, panicle /m2, grains / panicle and yield of rice. Data collected were subjected to Analysis of Variance and significant means were separated using Least Significant Difference (LSD) at p<0.05. The result showed that Rice plants treated with lambda-cyhalothrin at rate of 1L/ha, 0.75 L/ha, Carbofuran at rate of 10.0 kg/ha and 7.5 kg/ha had higher yield (2.90-2.97 tonnes/ha) compared with control (2.55 tonnes/ha). They also had lowest incidence (2.09-2.64%) and severity (2.40-3.72%) of O. oryzivora compared with 8.26-17.17% and 9.93- 14.72% in plants treated with lambda-cyhalothrin at 0.50 L/ha and control respectively. The parasitism of O. oryzivora was high on rice plants treated with Carbofuran and the untreated ones (1.16-1.74) compared with other application of lambda-cyhalothrin.

Association of voltage-gated sodium channel mutations with field-evolved pyrethroid resistant phenotypes in soybean aphid and genetic markers for their detection

The frequent use of insecticides to manage soybean aphids, Aphis glycines (Hemiptera: Aphididae), in the United States has contributed to field-evolved resistance. Pyrethroid-resistant aphids have nonsynonymous mutations in the voltage-gated sodium channel (vgsc). We identified a leucine to phenylalanine mutation at position 1014 (L1014F) and a methionine to isoleucine mutation (M918I) of the A. glycines vgsc, both suspected of conferring knockdown resistance (kdr) to lambda-cyhalothrin. We developed molecular markers to identify these mutations in insecticide-resistant aphids. We determined that A. glycines which survived exposure to a diagnostic concentration of lambda-cyhalothrin and bifenthrin via glass-vial bioassays had these mutations, and showed significant changes in the resistance allele frequency between samples collected before and after field application of lambda-cyhalothrin. Thus, a strong association was revealed between aphids with L1014F and M918I vgsc mutations and survival following exposure to pyrethroids. Specifically, the highest survival was observed for aphids with the kdr (L1014F) and heterozygote super-kdr (L1014F + M918I) genotypes following laboratory bioassays and in-field application of lambda-cyhalothrin. These genetic markers could be used as a diagnostic tool for detecting insecticide-resistant A. glycines and monitoring the geographic distribution of pyrethroid resistance. We discuss how generating these types of data could improve our efforts to mitigate the effects of pyrethroid resistance on crop production.

Toxicidad de insecticidas contra (Optatus palmaris Pascoe) en guanábana

Originario de América tropical, el guanábano (Annona muricata) tiene gran potencial y expectativa de producción en México. No obstante, presenta problemas de plagas que limitan su cultivo. Uno de estos es el picudo del fruto (Optatus palmaris), cuyo daño demerita la calidad y rendimiento. Se evaluaron los insecticidas y repelentes: spinosad, spinoteram, azadiractina, lambda-cialotrina, clorpirifos, imidacloprid y etofenprox. Se evalúo el porcentaje de mortalidad, consumo de fruta y se determinaron la CL50 y TL50. Una hora después de la aplicación se observó 89.2% y 85.7% (α< 0.05) de mortalidad con lambda-cialotrina y clorpirifos en concentración de 0.025 g ia L-1 y 2.4 g ia L-1, respectivamente. Spinosad y azadiractina no tuvieron efecto de mortalidad en concentraciones de 0.6 g ia L-1 y 32 g ia L-1, respectivamente (α< 0.05). A las 12 h después de la aplicación spinosad (0.6 g ia L-1), lambda-cialotrina (0.0012 g ia L-1) y clorpirifos (0.24 g ia L-1) ejercieron más de 95% de mortalidad (α< 0.05). El consumo de fruta fue menor con aplicación de lambda-cialotrina, 24.9% de fruta consumida (α< 0.05). El insecticida con mayor toxicidad fue imidacloprid con una CL50 de 0.06 g ia L-1 y TL50 de 0.3 h, le siguió el spinoteram con una CL50 de 0.96 g ia L-1 y un TL50 de 0.36 h. Azadiractina no ejerció mortalidad ni disminuyó el consumo de fruta comparado con el testigo absoluto en concentraciones de 0.32, 3.2 y 32 g ia L-1 (α< 0.05) por lo que no se recomienda el uso de este producto para el control de O. palmaris.

Field bioefficacy of mahogany seed extract (Khaya senegalensis: meliaceae, (desv.) a. juss) for management of bollworm infestation on cotton in Zaria, Nigeria

Field trials were conducted at two locations in Samaru (110 11'' N, 070 38'' E and 686m above sea level) and Maigana (110 10'' N, 070 37'' E and 675m above sea level) both in Northern Guinea Savannah ecological zone of Nigeria during the 2016 wet season to determine the effects of three concentration of aqueous Khaya seed extract (KSE) (20%w/v, 30%w/v and 40%w/v) on damage on cotton (SAMCOT 9) by bollworms. The experimental design was strip plot fitted into randomized complete block design. A total of four sprays at two weeks interval beginning from 9WAS (which corresponded to the period of formation of first square to the detection of first flower) were applied. Data were recorded on the number of terminal shoot damage, number of damaged shed squares, number of damaged shed cotton bolls and number of matured green bolls damaged by bollworms. There was no significant difference in the number of terminal shoot damaged by spiny bollworm (Earias spp.) from spray application of Lambda cyhalothrin, KSE and the untreated control. Significant reduction in the number of shed cotton squares, shed cotton bolls and matured green bolls damaged by bollworms were observed on Lambda cyhalothrin and 40%w/v KSE sprayed plots than the other treatments and the untreated control.

Timing of Lambda-Cyhalothrin and Pyriproxyfen Barrier Treatments for Aedes albopictus (Diptera: Culicidae) Management.

Barrier applications, treating vegetation and other potential mosquito resting areas with residual pesticides, have become standard practice for commercial pest management professionals offering mosquito control services. These treatments are generally effective in reducing numbers of the Asian tiger mosquito, Aedes albopictus (Skuse). In the temperate climates, adult Ae. albopictus populations are naturally eliminated each winter and must be grown from diapausing eggs the following spring. Therefore, early-season control interventions timed before populations rebound may further reduce population growth compared with interventions that take place after the population has peaked. We compared Early (1 June) barrier applications of lambda-cyhalothrin (Demand CS) mixed with the insect growth regulator pyriproxyfen (Archer IGR) to Late applications (31 July) in urban and suburban residential parcels in New Jersey. These applications resulted in 43 and 51% reductions in adult Ae. albopictus populations in the Early and Late intervention study parcels, respectively, when compared with the untreated Controls. Indirect applications of pyriproxyfen (i.e., rainwater runoff transferring pesticide) to potential larval habitat did not cause mortality in laboratory larval bioassays but direct mist applications of the Archer and Demand combination to larval habitats led to elevated larval mortality over a 6-wk period. The Early-season intervention offered no advantage in efficacy on adult populations compared with the Late-season intervention, which targeted peak mosquito populations. Our study provides support for the efficacy of barrier applications and illustrates the importance of timing barrier treatments to coincide with established Ae. albopictus action thresholds.

Impact of imidacloprid treated seed and foliar insecticide on Hessian fly abundances in wheat (Triticum aestivum L.)

Wheat, Triticum aestivum L., is a major crop of economic importance throughout the United States. The Hessian fly, Mayetiola destructor (Say), is a common economically important pest, feeding on wheat in the larval stage through the southeastern US. It is a multi-voltine species, with generation number dependent on temperature. Growers rely on various management approaches such as resistant wheat varieties, crop rotation, timely plantings, and insecticide treatments to control this destructive pest. The objectives for this research were to show the efficacy of a common insecticide seed treatment (imidacloprid) and a common foliar insecticide spray (lambda-cyhalothrin) on Hessian fly abundance in wheat. Four experiments were conducted over two years in North Carolina, in order to manipulate Hessian fly abundance. Small plot studies were designed with whole plot treatments including non-treated and imidacloprid treated wheat seed, and subplots split with a semi-monthly foliar lambda-cyhalothrin application or no foliar insecticide. The number of Hessian fly eggs present on leaves, number of larvae, number of pupae, and tiller density were counted for the fall generation(s) and all plots were sprayed with foliar insecticide during the spring. Wheat seed treated with imidacloprid had fewer eggs, larvae, and pupae compared to other non-treated seed. With one exception during 2014, foliar spray applications did not reduce egg, larvae, and pupae abundance. Warmer temperatures during 2015 experiments provided conditions that extended Hessian fly presence, allowing multiple fall generations to infest wheat. Unlike 2014 experiments, foliar sprays in 2015 experiments provided some protection from Hessian fly.

Lower incidence of yellow dwarf disease in autumn-sown wheat crops in New Zealand is linked with sowing dates, insecticide regimes and aerial aphid numbers

Symptoms of yellow dwarf disease caused by Luteoviridae viruses (YDV) in each of 43–75 autumn-sown wheat crops per year were monitored for six years during 1998–2005 in Canterbury, New Zealand. They were related to seed and foliar insecticide applications and the numbers of YDV aphid vectors from one to four regional 7.5 m high suction traps during the crop emergence–GS 30 virus infection-risk period. Over the five years when YDV was assessed in each crop on visual symptoms at flag leaf, the YDV incidence in untreated crops tended to increase with increasing numbers of flying aphids. When aphid numbers were below a relatively low threshold during the risk period for each crop, YDV incidence was low irrespective of insecticide treatments. Above this aphid threshold, the incidence of YDV was lowest in crops with an insecticide programme of an imidacloprid seed treatment followed by one foliar application of lambda-cyhalothrin at 17–24 g ai ha−1. This regime was estimated to provide protection from aphid-transmitted virus infection for approximately 50 % of the risk period irrespective of sowing date. Wheat crops treated with an imidacloprid-seed treatment plus one insecticide foliar application had 96 % less virus incidence than untreated crops, and one foliar application alone had 70 % less incidence. These results suggest that a tool incorporating aphid flight patterns and wheat growth stages could be developed to optimise insecticide applications for control of secondary aphid incursions in autumn sown wheat crops in New Zealand.

Effects of Diamide Insecticides on Predators in Soybean.

Predatory arthropods can be important for preventing insect pests from reaching damaging levels in soybean. However, the predator community can be compromised when pest control strategies include the application of broad-spectrum insecticides. The use of selective insecticides such as diamides could conserve predators while still providing necessary pest control. We evaluated two selective diamide insecticides, chlorantraniliprole and flubendiamide, and a broad-spectrum insecticide, lambda-cyhalothrin in combination with chlorantraniliprole, for impact on predators in soybean. We applied insecticides to field plots and documented predator abundance prior to and up to 3 wk postapplication using sticky card, beat sheet, and sweep net sampling methods. In sweep net samples, total predator abundance in plots treated with the selective insecticides was not significantly different from untreated control plots. For beat sheet samples, there were no significant differences in the abundance of total predators on any day postapplication between the selective diamide insecticides or the untreated control, but abundance decreased after application of lambda-cyhalothrin + chlorantraniliprole and did not recover. For sticky cards, there were no differences in predator abundance among treatments on any day postapplication. Over all, results showed that there were no significant differences in the abundance of total predators, Anthocoridae, Araneae, or Geocoridae after application of flubendiamide or chlorantraniliprole compared with the untreated control for up to 3 wk after application. All insecticides significantly decreased populations of lepidopteran pests compared with the untreated control, but only lambda-cyhalothrin + chlorantraniliprole reduced predatory arthropod abundance.

Dissipation pattern and risk assessment of the synthetic pyrethroid Lambda-cyhalothrin applied on tomatoes under dryland conditions, a case study

The present study was carried out to develop and validate an analytical method for the detection and quantification of lambda-cyhalothrin, a synthetic pyrethroid insecticide, in tomato using gas chromatography-electron capture detector (GC-ECD). The study has meant to ascertain lambda-cyhalothrin dissipation behavior under dry land conditions. The analytical method was validated using blank tomato spiked at 0.01, 0.1 and 0.5 mg/kg, with satisfactory recoveries ranging between 92.3 to 95.1 % and relative standard deviations (RSDs) < 13.4 %. Good linearity was achieved, with a determination coefficient (R 2) of 0.999 for the 0.005–2.0 mg/L concentration range. The limits of detection and quantification were 0.005 and 0.01 mg/kg, respectively. Dissipation pattern of lambda-cyhalothrin applied on open field grown tomato was also assessed using the same method. Lambda-cyhalothrin residues declined very quickly following first-order rate kinetics with half-life of 3.12 days. At harvest time, 14 days after final application, the remaining residues of lambda-cyhalothrin were below CODEX maximum residue limit (MRL) of 0.05 mg/kg. Exposure of lambda-cyhalothrin has been assessed and compared to acceptable daily intake (ADI). The assessment of consumers’ exposure was based on the international estimated daily intake (IEDI) compared to acceptable daily intake (ADI). The long-term risk assessment was performed by calculating the hazard quotient (HQ). Since the HQChronic of lambda-cyhalothrin never exceeded 1.2 %, the tomato fruits could be considered safe for human consumption 14 days after application of lambda-cyhalothrin at the recommended dose.

Lambda-cyhalothrin efficiency on fruit borer control and quali-quantitative spraying aspects in a pinecone crop

ABSTRACT In Brazil, the state of Bahia is one of the largest pinecone (Annona squamosa L.) growers; nevertheless, fruit borer (Cerconota anonella L.) presence limits production. This research aimed to test the efficiency of lambda-cyhalothrin in controlling fruit borer using different spray volumes; additionally, this research tested qualitative and quantitative operational aspects. Trials were carried out in pinecone orchards in Caraíbas-BA, Brazil. Pesticide efficiency was tested by a randomized block experiment with six treatments and five replications. Treatments consisted of lambda-cyhalothrin application (1.5 g a.i. 100 L-1 water) with a surfactant (0.03% v v-1) at spray volumes of 100, 200, 268, 382 and 488 L ha-1 and one control (without spray). Pest infestation was assessed by counting symptomatic fruits for further percentage calculation. Five treatments with five replications were developed to evaluate spraying performance. These treatments consisted of an aqueous solution with a Brilliant Blue tracer at 0.15% (p v-1) and a surfactant at 0.03% (v v-1), using the same spray volumes as the first experiment. Qualitative assessments were performed on water-sensitive paper cards and were quantified through tracer deposit levels on leaves. Spray volumes between 100 and 382 L ha-1 with lambda-cyhalothrin were efficient to control Cerconota anonella in the pinecone crop, providing good quality application.

Insecticide Efficacy and Timing for Control of Western Bean Cutworm (Lepidoptera: Noctuidae) in Dry and Snap Beans.

The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a recent pest of corn, dry,and snap beans, in the Great Lakes region, and best practices for its management in beans need to be established.Insecticide efficacy and application timing field studies, conducted in 2011–2013, determined that lambda-cyhalothrin and chlorantraniliprole were capable of reducing western bean cutworm feeding damage in dry beans from 2.3 to 0.4% in preharvest samples, and in snap beans from 4.8 to 0.1% of marketable pods, respectively. The best application timing in dry beans was determined to be 4–18 d after 50% egg hatch. No economic benefit was found when products were applied to dry beans, and despite high artificial inoculation rates, damage to marketable yield was relatively low. Thiamethoxam, methoxyfenozide, and spinetoram were also found to be effective at reducing western bean cutworm damage in dry bean to as low as 0.3% compared to an untreated control with 2.5% damaged pods. In snap beans, increased return on investment between CAD$400 and CAD$600 was seen with multiple applications of lambda-cyhalothrin, and with chlorantraniliprole applied 4 d after egg mass infestation.

Targeted control of the saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae), and the benefits of good control of this pest to winter wheat yield.

Since 2010 there has been a resurgence of the saddle gall midge, Haplodiplosis marginata (von Roser), in Belgium and several other European countries, with this pest sometimes causing severe damage in cereals. In 2012 and 2013, field trials were conducted in heavily infested fields to assess its impact on winter wheat crops and to determine efficient ways of dealing with severe infestations. Crop exposure to H. marginata varied with the different protection methods tried. These methods included 1-4 successive applications of lambda-cyhalothrin. Yield losses were significant, reaching 6% in 2012 and as high as 15% in 2013, and these losses were linearly related to the number of galls on stems. The trials showed that insecticide applications needed to be synchronised with H. marginata flight peaks and to target the egg hatching period. They also revealed that insecticides applied to coincide with the first flight could, in humid conditions, also reach the larvae close to the soil surface, prior to their pupation.

Susceptibility of Sesame (Sesamum indicumL.) to Major Field Insect Pests as Influenced by Insecticide Application in a Sub-Humid Environment

Eighteen sesame varieties were tested in the field for their responses to major insect pests with or without insecticide application. Insect pest density was higher in the unsprayed plots than the sprayed plots, except Myzus persicae whose density was significantly higher in the sprayed plots. Lower insect density was recorded on Yobe-Chambamba, while higher pest density was recorded on Domu, in late season. Yobe-Chambamba and Eva were not attacked by M. persicae. Leaf and capsule damage were significantly lower (2 % each) on Yobe-Chambamba.Amongthe varieties,Yobe-Chambambacarried the least pest population intensity, while highest pest density was recorded on Domu, NCRIBEN-01M, Yobe-gadaka, 530-6-1, Cross-95, E-8, PB-Til, Ciano-16 and Cameroun white. Lambda-cyhalothrin application significantly reduced pest density in the early season but not capsule damage or any of the plant characteristics measured. The use of lambda-cyhalothrin may not be necessary for the control of insect pests on sesame in the expe...

Biological endpoints, enzyme activities, and blood cell parameters in two anuran tadpole species in rice agroecosystems of mid-eastern Argentina

Different biological variables of tadpoles, including survival, development and growth rates, and biomarkers [cholinesterases, glutathione-S-transferases (GST), and blood cell morphology] were evaluated in two anuran species, Scinax squalirostris (Hylidae) and Leptodactylus mystacinus (Leptodactylidae), using in situ experimental chambers in a rice field (RF) sprayed with insecticide Lambda-cyhalothrin (LTC) by aircraft in Santa Fe Province, Argentina. We found a significant decrease in body weight (0.62 ± 0.04 g) of L. mystacinus and an increased development rate of S. squalirostris in individuals from RF (41 ± 1; Gosner) with respect to individuals from the reference site (RS: 0.93 ± 0.04 g and 37 ± 0; respectively). In S. squalirostris, individuals from RF mean values of butyrylcholinesterase activities decreased at 48 (4.09 ± 0.32 nmol min-1 mg-1 of TP) and 96 h (3.74 ± 0.20 nmol min-1 mg-1 of TP), whereas inhibition of acetylcholinesterase was observed at 96 h (47.44 ± 2.78 nmol min-1 mg-1 of TP). In L. mystacinus from RF, an induction of acetylcholinesterase activity was observed at 96 h (36.01 ± 1.09 nmol min-1 mg-1 of TP). Glutathione-S-transferase levels varied between species, being higher in L. mystacinus individuals but lower in S. squalirostris from RF at 48 (272.29 ±11.78 and 71.87 ± 1.70 nmol min-1 mg-1 of TP; respectively) and 96 h (279.25 ± 13.06 and 57.62 ± 4.58 nmol min-1 mg-1 of TP, respectively). Blood cell parameters revealed a lower number of mitotic cells (MC: 0.36 ± 0.31%o for S. squalirostris and 0.08 ± 0.05 %o for L. mystacinus) and higher number of eosinophils (E: 3.45 ± 1.75 %o for S. squalirostris and 7.64 ± 0.98 %o for L. mystacinus) in individuals from the RF than in individuals from the RS (MC: 2.55 ± 0.74 %o for S. squalirostris and 1.87 ± 0.72%o for L. mystacinus; and E: 0.13 ± 0.09 for S. squalirostris and 3.20 ± 0.80 for L. mystacinus). Overall, our results demonstrate the existence of apparent differences in sensitivity between species in a series of sublethal responses to short-term exposure in RF after the application of Lambda-cyhalothrin. We suggest that the integral use of biological endpoints (development and growth) together with biomarkers (cholinesterase, GST, and blood cell parameters) may be a promising integral procedure for investigating pesticide exposure in wild frog populations.

Impact of Phlebotomine Sand Flies on United State Military Operations at Tallil Air Base, Iraq: 6. Evaluation of Insecticides for the Control of Sand Flies

We conducted a series of field experiments in 2003 and 2004 to evaluate the efficacy of a variety of insecticides and insecticide application technologies for the control of phlebotomine sand flies at Tallil Airbase, Iraq. During the experiments, 53,263 sand flies were collected. The experiments evaluated the following: (1) routine sand fly control operations using a variety of residual and area-wide insecticides; (2) a combination of five different insecticide application methods in and around tents; (3) residual application of lambda-cyhalothrin and ultra-low volume application of pyrethrins in houses; (4) carbaryl and lambda-cyhalothrin applied as barrier sprays; (5) a deltamethrin-impregnated fence; (6) lambda-cyhalothrin applied as a residual spray in concrete manholes; (7) deltamethrin-treated flooring in tents; and 8) ultra-low volume-applied malathion. Although some of the experiments resulted in limited reductions in the number of sand flies collected in light traps, in no instance did we completely eliminate sand flies or reduce populations for a sustained period. The implications of these findings are discussed.

Evaluación de la actividad tóxica de los insecticidas piretroides deltametrina y lambdacihalotrina en dos poblaciones de campo de Rhodnius pallescens (Hemíptera: Reduviidae) de Panamá

Introduction. Systematic evaluation of the susceptibility of disease vectors to insecticides permits the detection of the development of insecticide resistance over time. This is necessary to evaluate the effectiveness of control methods and to plan management strategies of the resistance.Objective. The baseline susceptibility was determined for I and V instar nymphs of Rhodnius pallescens to the active ingredients of the insecticides deltamethrin and lambdacyhalothrin.Materials and methods. The bioassays were applied to two field populations of R. pallescens collected in Chilibre and Cerro Cama, Panamá. A standard protocol for topical application was adapted from that developed for Rhodnius prolixus. Bioassays were performed using topical applications on the dorsal abdominal surface, with volumes of 0.1 &mu;l and 0.5 &mu;l acetone solution of insecticide for nymphs of stage I and V respectively, using 5 &mu;l and 25 &mu;l Hamilton microsyringes with a repeating dispenser. Ten nymphs were used for each insecticide concentration.Results. With the topical application of lambdacyhalothrin on first-instar nymphs from Chilibre and Cerro Cama, the LD50 values expressed in ng/insect were 0.13 and 0.11 respectively. In fifth-instar nymphs the LD50 values were 1.71 and 3.48, respectively. For deltamethrin, the topical application on first-instar nymphs resulted in LD50 values of 0.02 and 0.02, and in fifth-instar nymphs the LD50 values were 2.11 and 1.55, respectively.Conclusions. In I and V instar nymphs from the two R. pallescens populations, resistance factor values demonstrated no significant difference in the toxic effects of the two insecticides and indicated that the R. pallescens populations were susceptible them.

The Impact of Planting Date on Management of the Rice Water Weevil in Louisiana Rice

The rice water weevil, Lissorhoptrus oryzophilus, is the most destructive insect pest of rice in the United States. Early planting of rice to avoid damaging infestations of the rice water weevil has long been suggested as a management tactic. A five-year study was conducted to characterize the influence of rice planting date on rice water weevil manage- ment in light of recent trends toward earlier planting of rice in Louisiana. Experimental designs differed among years: ex- periments in 2001 and 2008 were split-plot studies, whereas in 2003, 2004, and 2007, separate randomized block experi- ments were conducted. Results from these experiments showed that early planting of rice facilitated rice water weevil management in three ways. Weevil infestations were lighter in rice planted in mid- to late March than in later-planted rice in three of five years of the study. In addition, yield losses attributable to weevil feeding were lower in early planted rice than in late planted rice in the two split-plot experiments. Finally, single applications of lambda-cyhalothrin (a pyrethroid applied to rice after flooding to kill weevil adults) were less effective in late planted rice than in early planted rice. This study demonstrates that early planting can serve as an important component of a management program for rice water wee- vils in Louisiana.

The application of lambda-cyhalothrin in tick control

In recent years, in urban areas of Novi Sad, unique ecological conditions, specific floristic and faunistic composition and poor habits of citizens in sense of public health, facilitate the development and maintenance of ticks. Regarding the importance of ticks as vectors of severe human and animal diseases, complex and detailed studies are conducted with an aim to find the most efficient methods for tick control. Two tick species, Ixodes ricinus and Dermacentor marginatus, were identified during a 3-year period on the territory of Municipality of Novi Sad. During 2006, the efficacy of the pyrethroid lambda-cyhalothrin in tick control varied from 60.7 to 100%. The highest efficacy recorded in 2007 was 92.3%. The efficacy of lambda-cyhalothrin in 2008 varied from 39.1 to 100%. Lambda-cyhalothrin showed high efficacy in tick control at localities which were improved before the application (mowed, litter removed, abundance control and euthanasia of abandoned cats and dogs). The results of this research indicate that lambda-cyhalothrin has a toxic effect on ticks and could be used as efficient acaricide for tick control, although its efficacy depends on formulation, terrain features and methods of application.