High‐throughput screening method for evaluating spatial repellency and vapour toxicity to mosquitoes

Spatial repellents are an essential tool for personal protection against mosquitoes that bite and transmit disease pathogens to humans. Current repellent screening methods, such as olfactometers and alternative choice tests, are complex systems that require a relatively large quantity of compound (mg). The present study validates a high‐throughput spatial repellent screening method using a glass tube that has the ends covered with netting, in addition to treated filters and plastic end caps. The apparatus occupies relatively little space, is easy to decontaminate, and requires small amounts of compound (μg). In a horizontal tube orientation, DEET (N,N‐diethyl‐meta‐toluamide), citronella oil and IR3535 had 1 h half repellent concentration (EC₅₀) values of 32, 32 and 298 μg/cm², respectively, against the Orlando strain of Aedes aegypti (L.) (Diptera: Culicidae). Vertical tube orientation increased EC₅₀ values by approximately two‐fold, except IR3535, which remained essentially unchanged. Transfluthrin showed concentration‐dependent spatial repellency (1 h EC₅₀ = 0.5 μg/cm²) without any knockdown, although only in vertical tubes. Transfluthrin showed 50% knockdown in 1 h at 0.5 μg/cm² and 50% mortality at 0.15 μg/cm² in horizontal tubes. In conclusion, this high‐throughput screening method is useful for assessing vapour toxicity and the spatial repellency of candidate molecules prior to semi‐field and field studies.     

Fumigant toxicity of Carum copticum L. (Apiaceae) essential oil on Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) adults under greenhouse conditions

Greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) is one of the most injurious pests of greenhouse crops and ornamental plants in worldwide, both outdoor and indoor. This insect, feeding on plant sap, producing honeydew and transmitting plant viruses, causes quantitative and qualitative damages in plants. For controlling this pest in greenhouse, plant essential oils are mentioned instead of chemical insecticidal. So, in this research, fumigant toxicity of Carum copticum L. (Fam.: Apiaceae) plant oil on mentioned adult pest was surveyed. Dry ground seeds were subjected to hydrodistillation using a modified Clevenger-type apparatus and the resulting oil contained Thymol (50.07%), Gama-Terpinene (23.99%), P-Cymene (22.9%), Myrcene (0.51%) and 1,8-Cineole (0.5%). All bioassay tests were conducted at 27?±?2?°C, 65?±?5 RH and a photoperiod of 16:8?h (light: dark). This research was performed with a completely random design with six treatments (five different concentrations of essential oils plus control). Each concentration includes of three replicates and each replicate consisted of 20 adult of pests. The results showed that aforementioned essential oil shows significant mortality of adults 24?h after exposure. The value LC₅₀ of mentioned plant oil on T. vaporariorum was 1.03?μl?L/L air. And mortality percentage shows higher sensitivity of T. vaporariorum against application of essential oil. The value LT₅₀ estimated for T. vaporariorum in concentration of 1.03?μl?L/L air was 7.18?h. Fumigant toxicity this essential oil has had an ordered relationship with the concentration and time exposure. The results of this research showed that mentioned plant oil had appropriate insecticidal effects on these greenhouse pests. The findings showed that C. copticum L. oil has high impact on the above-mentioned pests and it is suggested because of its high potential in fumigant toxicity and its use in integrated pest management programmes in greenhouses is mentioned.     

Miticide bioassays with spider mites (Acari: Tetranychidae): effect of test method,exposure period and mortality criterion on the precision of response estimates

Six different bioassay methods were evaluated using propargite (Omite 30% wettable powder (WP) and fenbutatin oxide (Torque 50% (WP) and 55% suspension concentrate (SC)) with twospotted spider mite, Tetranychus uriticae Koch (TSM) and European red mite, Panonychus ulmi Koch (ERM) to document their utility and precision for estimating median lethal concentrations (LC). For each method, two post-treatment exposure periods and mortality criteria were used. Post-treatment exposure period and mortality criterion had a significant influence on the precision of LC₅₀ estimates for all tested miticides with all bioassays methods. Twenty four hour (h) post-treatment exposure was found to be the most suitable for the slide dip and Petri dish methods while 48h was the most appropriate for leaf disc methods. Scoring moribund mites as dead was the most satisfactory criterion for ensuring that biossays were as simple and precise as possible. The Petri dish residue-Potter tower method (PDR-PT) estimated the responses of TSM and ERM to propargite with high precision. The same method was not as precise for fenbutatin oxide formulations. Because significant mite run-off occurred with the leaf disc methods, their precision was not fully established. The slide dip method gave less precise estimates of LC₅₀ values for propargite (WP) and fenbutatin oxide (WP), while the same method gave more precise LC₅₀ estimates for fenbutatin oxide (SC) than the PDR-PT method. The toxicity of candidate miticides was found to be method-and species-dependent.     

印度藏茴香植物精油对温室棉蚜的熏蒸毒性及其成分分析（英文）

【目的】棉蚜Aphis gossypii是世界各地室内和室外果树、蔬菜和观赏植物上最具危害性的害虫之一。这一害虫取食植物汁液,产生蜜露,传播植物病毒,对植物从质和量上产生破坏。为了控制温室中的这一害虫,植物精油可用作化学农药的替代药物。本实验研究了印度藏茴香Carum copticum植物精油对棉蚜成虫的熏蒸毒性。【方法】将研磨的印度藏茴香干种子用改良的挥发油提取器(Clevenger-type apparatus)进行水蒸馏。所有生物测定均在27±2℃,相对湿度65%±5%和光周期16L∶8D条件下进行。研究采用完全随机设计,6个处理(5个不同浓度的精油加对照)。每一浓度3次重复,每一重复20头成虫。【结果】结果表明,棉蚜成蚜接触印度藏茴香精油24 h后出现明显的死亡。该精油对棉蚜成蚜的致死中浓度(LC50)为1.21μL/L空气。棉蚜成蚜的死亡百分率对精油的施用表现出较高的敏感性。精油浓度为1.21μL/L空气时,估计的棉蚜的致死中时(LT50)为11.79 h。这一精油的熏蒸毒性与浓度和接触时间之间具有一定的相关性。GC/MS组分分析结果表明,该精油由18种化合物组成,最重要的是一些化合物引起了熏蒸毒性,如麝香草酚(占50.07%)、γ-萜品烯(占23.99%)和对异丙基苯甲烷(占22.90%)。【结论】本研究结果表明印度藏茴香植物精油对棉蚜具有较好的杀虫效果。印度藏茴香精油对棉蚜产生较大的影响,由于它具有较高的熏蒸毒性潜力,因此可在温室中用于这一害虫的综合治理。     

Insecticidal activity of Citrus aurantium peel extract against Bactrocera oleae and Ceratitis capitata adults (Diptera: Tephritidae)

Citrus aurantium (L.) peel extracts in petroleum ether were evaluated for toxicity against olive fruit fly, Bactrocera oleae (Gmelin) and medfly, Ceratitis capitata (Wiedemann) adults. Bactrocera oleae flies were more susceptible to the extract than C. capitata in contact and residual bioassays. Fumigation bioassay had no effect. Both sexes of B. oleae were equally susceptible in both types of bioassays. However, males of C. capitata were more susceptible than the conspecific females. LD₅₀ values (concentration causing 50% mortality) after 96 h for the males and females of B. oleae were 44.8 and 40.1 μg/insect in contact bioassay through topical application. Whereas, LD₅₀ values for the males and females of C. capitata were 38.8 and 67.8 μg/insect respectively. LC₅₀ values after 96 h for the males and females of B. oleae were 18.8 and 17.8 μg/cm² in Petri dish residual bioassay. Whereas, LC₅₀ values for the males and females of C. capitata were 70.6 and 147.1 μg/cm² respectively.
Fractionation of the extract on a silica gel column with three different polarity solvents resulted in three fractions with only the intermediate polarity solvent fraction having substantial insecticidal activity. Toxicity of the mixtures of active and inactive fractions was equal to the original extract. Our results indicate that C. aurantium has potential for controlling insect pests.     

Insecticidal effects of Artemisia dracunculus L. (Asteraceae) essential oil on adult of Aphis gossypii Glover (Hemiptera: Aphididae) under laboratory conditions

Aphis gossypii Glover (Homoptera: Aleyrodidae) is one of the most important pests of agriculture worldwide. To control the pest population, research on the use of the environmental and plant-based compounds has increased in recent decades. So, in this study, effect of fumigant toxicity of Artemisia dracunculus L. essential oil on adults of the mentioned pest was studied. The essential oil of this plant was subjected to hydro-distillation using a Clevenger apparatus. All bioassay examinations were conducted at 27?±?2 and 65?±?5?°C relative humidity and a photoperiod of 16:8?h (light:dark). This research was performed in a completely random design with six treatments in different concentrations and times to evaluate the level of LC₅₀ and LT₅₀. Each treatment was evaluated in three replicates for different concentrations and times with each replicate consisting of 20 same-age adult pests. The results showed that the use of the essential oil of A. dracunculus L. shows significant mortality of pest 24?h after treatment. LC₅₀ value of this essential oil on adults of A. gossypii was 18.63?μL/L of air and LT₅₀ value of the essential oil on the mentioned pest resulted to be 10.74?h with a concentration of 18.63?μL/L of air. The results showed that by increasing the concentration and duration of essence treatment, the mortality rate also increased. Experiment results showed that A. dracunculus L. oil has strong effect on the above-mentioned pest and it will be suggested for using in the mentioned integrated pest management programmes in greenhouses for its high potential in fumigant toxicity.     

The plasminogen receptor,Plg-RKT,plays a role in inflammation and fibrinolysis during cutaneous wound healing in mice

Wound healing is a complex physiologic process that proceeds in overlapping, sequential steps. Plasminogen promotes fibrinolysis and potentiates the inflammatory response during wound healing. We have tested the hypothesis that the novel plasminogen receptor, Plg-R_KT, regulates key steps in wound healing. Standardized burn wounds were induced in mice and time dependence of wound closure was quantified. Healing in Plg-R_KT^−/− mice was significantly delayed during the proliferation phase. Expression of inflammatory cytokines was dysregulated in Plg-R_KT^−/− wound tissue. Consistent with dysregulated cytokine expression, a significant delay in wound healing during the proliferation phase was observed in mice in which Plg-R_KT was specifically deleted in myeloid cells. Following wound closure, the epidermal thickness was less in Plg-R_KT^−/− wound tissue. Paradoxically, deletion of Plg-R_KT, specifically in keratinocytes, significantly accelerated the rate of healing during the proliferation phase. Mechanistically, only two genes were upregulated in Plg-R_KT^−/− compared with Plg-R_KT^+/+ wound tissue, filaggrin, and caspase 14. Both filaggrin and caspase 14 promote epidermal differentiation and decrease proliferation, consistent with more rapid wound closure and decreased epidermal thickness during the remodeling phase. Fibrin clearance was significantly impaired in Plg-R_KT^−/− wound tissue. Genetic reduction of fibrinogen levels to 50% completely abrogated the effect of Plg-R_KT deletion on the healing of burn wounds. Remarkably, the effects of Plg-R_KT deletion on cytokine expression were modulated by reducing fibrinogen levels. In summary, Plg-R_KT is a new regulator participating in different phases of cutaneous burn wound healing, which coordinately plays a role in the interrelated responses of inflammation, keratinocyte migration, and fibrinolysis.Subject terms: Extracellular matrix, Mechanisms of disease     

Rapid bioassay of aluminum toxicity in soil

Fifty-five acid soil horizons from 19 profiles were evaluated for aluminum toxicity using root elongation as a criterion in a two-day petri dish bioassay. The method proved to be simple, efficient, and precise enough to clearly distinguish aluminum toxicity differences among horizons within and between profiles. Although toxicity patterns within profiles differed, it was common for surface horizons to be less toxic even when very acid. The R² for correlations of relative root lengths with pH in H₂O, pH in KCl, soluble and exchangeable aluminum and percent aluminum saturation were only 0.42, 0.45, 0.52, 0.66, and 0.54, respectively, which indicates the need for a bioassay. In a further use of the method, and to demonstrate its efficiency, 243 horizons from 26 profiles were screened. Approximately half of the horizons with a pH of 5.0 or below showed Al toxicity. When used by different operators, with a variety of soil and treatment parameter changes, the two-day bioassay in petri dishes gave consistent rankings of soils by degree of aluminum toxicity. Journal Paper 11690, Purdue University, Agricultural Experiment Station, West Lafayette, Indiana, USA. Contribution from the Agronomy Department.     

Sensitivity of Aedes aegypti adults (Diptera: Culicidae) to the vapors of Eucalyptus essential oils

Vapors of essential oils extracted from various species of Eucalyptus (E. gunnii, E. tereticornis, E. grandis, E. camaldulensis, E. dunnii, E. cinerea, E. saligna, E. sideroxylon, E. globulus ssp. globulus, E. globulus ssp. maidenii, E. viminalis and the hybrids E. grandis × E. tereticornis and E. grandis × E. camaldulensis) and their major components were found to be toxic to Aedes aegypti adults, the yellow fever mosquito.An aliquot of each oil was placed in a cylindrical test chamber and the number of knocked-down mosquitoes was recorded as function of time. Knockdown time 50% was then calculated. Results showed that E. viminalis had the fastest knockdown time at of 4.2 min, on the same order as dichlorvos, a standard knockdown agent. A correlation was observed between the content of 1,8-cineole in the Eucalyptus essential oils and the corresponding toxic effect.The correlation between KT₅₀ values and calculated vapor pressures of the essential oil components showed that the fumigant activity of simple organic compounds in insects is correlated with their volatility.     

水菖蒲活性物质β-细辛醚对四种储粮害虫的熏蒸活性

植物性次生物质在植物-害虫的关系中起着非常重要的作用, 植物中的一些成分对害虫具有熏蒸、触杀和驱避等作用。水菖蒲Acorus calamus L.是一种常用中药, 它的主要杀虫活性成分为β-细辛醚。本研究通过室内生测试验研究了水菖蒲根茎提取物β-细辛醚对玉米象Sitophilus zeamais Motschulsky、谷蠹Rhyzopertha dominica (Fabricius)、赤拟谷盗Tribolium castaneum (Herbst)和四纹豆象Callosobruchus maculatus (Fabricius) 4种储粮害虫的熏蒸击倒和致死作用。结果表明: β-细辛醚对4种试虫的熏蒸击倒和致死作用明显。以50 μL/L的浓度处理120 h后, 对玉米象、谷蠹和四纹豆象的击倒作用均达到100%, 而对赤拟谷盗击倒率为50%; 玉米象、谷蠹和四纹豆象的死亡率分别为81.23%, 97.78%和100%, 而赤拟谷盗死亡率仅为8.89%。处理24 h, β-细辛醚对玉米象、谷蠹、赤拟谷盗和四纹豆象的KC50分别为49.38, 102.96, 124.04和1.07 μL/L; 处理120 h, β-细辛醚对玉米象、谷蠹、赤拟谷盗和四纹豆象的LC50分别为17.82, 4.42, 116.48和0.73 μL/L。结果显示水菖蒲根茎提取物β-细辛醚对4种储粮害虫均具有明显的熏蒸效果, 具有开发为储粮害虫熏蒸剂的潜力。     

Efficacy of some plants as a post-harvest protectant against some major stored pests

The toxicity of vapours of the essential oil of Ferula gummosa, Elettaria cardamomum and Salvia officinalis on the adults and larvae of some stored product pests was investigated. The bioassays were carried out in 70 mL vials containing 10 individuals of each insect. The LC₅₀ values of fumigant bioassay after 24 h were calculated. Results indicated that the effect of the essential oil of F.gummosa was stronger than E. cardamomum, S. officinalis on stored pests. Also fumigant toxicity of S. officinalis on Sitophilus oryzae was similar to that of Sitophilus granarius adults. On the other hand, R. officinalis had a good effect on adults of Tribolium castaneum and larvae of Ephestia kuehniella. According to our results and good effect of these compounds, they will be a safe replace for chemical compounds in the future.     

Bioactivity of semisynthetic eugenol derivatives against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae infesting maize in Colombia

The anti-acetylcholinesterase, larvicidal, antifeedant activities and general toxicity of 15 semisynthetic eugenol derivatives based on clove oil (including the own oil), were evaluated against the maize armyworm, Spodoptera frugiperda (J.E. Smith). Therefore, promising eugenol molecules were classified with larvicidal, anti-acetylcholinesterase and antifeedant activities for controlling this pest. During structure–activity relationship studies and physicochemical profile analysis, it was found that among tested molecules 1–15, eugenol 1, prenyl eugenol 4, isoeugenol 8 and isoeugenol acetate 11 exhibited lethal effects LD₅₀ at concentrations <1 mg/g of insect. On the other hand, eugenol 1, metallyl eugenol 3, isoeugenol 8 and isoeugenol acetate 11 showed a good antifeedant activity (CE₅₀ = 158–209 µg/mL) with a high antifeedant index (70–78%) at concentration 1000 µg/mL, possessing a weak anti-acetylcholinesterase activity (IC₅₀ = 21–31 μg/mL). According to their ecotoxicological profiles (LC₅₀ = 2033.1–6303.8 µg/mL on Artemia salina larvae), isoeugenol 8 and its acetate derivative 11 could be potential used in control of the growth, feeding, or reproduction of S. frugiperda larvae, acting as moderate insecticidal acetylcholinesterase inhibitors and/or antifeedant molecules. Such structure–activity relationship studies could stimulate the identification of lead structures from natural sources for the development of larvicidal and deterrent products against S. frugiperda and related insect pests.     

Acaricidal effects of <Emphasis Type="Italic">Corymbia citriodora</Emphasis> oil containing <Emphasis Type="Italic">para</Emphasis>-menthane-3,8-diol against nymphs of <Emphasis Type="Italic">Ixodes ricinus</Emphasis> (Acari: Ixodidae)

The toxicity of para-menthane-3,8-diol (PMD), the main arthropod-repellent compound in the oil of the lemon eucalyptus, Corymbia citriodora, was evaluated against nymphs of Ixodes ricinus using five methods (A–E) of a contact toxicity bioassay. Mortality rates were estimated by recording numbers of dead nymphs at 30 min intervals during the first 5 h after the start of exposure and at longer intervals thereafter. The mortality rate increased with increasing concentration of PMD and duration of exposure with a distinct effect after 3.5 h. From the results obtained by methods A, C and E, the LC₅₀ range was 0.035–0.037 mg PMD/cm² and the LC₉₅ range was 0.095–0.097 mg PMD/cm² at 4 h of exposure; the LT₅₀ range was 2.1–2.8 h and the LT₉₅ range was 3.9–4.2 h at 0.1 mg PMD/cm². To determine the duration of toxic activity of PMD, different concentrations (0.002, 0.01, 0.1 mg PMD/cm²) were tested and mortality was recorded at each concentration after 1 h; thereafter new ticks were tested. This test revealed that the lethal activity of PMD remained for 24 h but appeared absent after 48 h. The overall results show that PMD is toxic to nymphs of I. ricinus and may be useful for tick control.     

Toxicity of Chemically Spiked Sediment to the Carpet Shell Clam Ruditapes decussatus Embryos and Larvae

The objective of this research was to assess the toxicity of sediment contaminated with cadmium, DDT, chlorpyrifos, and fluoranthene to embryos and larvae of the European clam Ruditapes decussatus, exposed to two sediment fractions, the whole sediment and elutriate. The percentages of abnormal D-shaped larvae and larval mortality have been investigated. The median effective concentration (EC50) values, reducing 50% of the percentage of D-shaped larvae, in whole sediments and elutriates were, respectively, 1.17 mg/kg and 417.1 μgl^?1 (3.71 μM) for cadmium, 1.66 mg/kg and 97.8 μgl^?1 (0.48 μM) for fluoranthene, 1.71 mg/kg and 384.8 μgl^?1 (1.08 μM) for DDT, and 0.96 mg/kg and 339.5 μgl^?1 (0.96 μM) for chlorpyrifos. The 96h-median lethal concentrations (LC50) reducing larval survival by 50% were 4.04 mg/kg 654.3 μgl^?1 (5.82 μM) for cadmium, 17.41 mg/kg 8666.6 μgl^?1 (42.84 μM) for fluoranthene, 3.93 mg/kg and 457.4 μgl^?1 (1.29 μM) for DDT, and 2.53 mg/kg and 308.06 μgl^?1 (0.87 μM) for chlorpyrifos. Based on EC₅₀ and LC₅₀ comparisons to toxicity data for other marine species, these findings suggest that the R. decussatus embryotoxicity and larvae mortality bioassay were among the most sensitive tools for sediment quality assessment.     

In a warmer Arctic,mosquitoes avoid increased mortality from predators by growing faster

Climate change is altering environmental temperature, a factor that influences ectothermic organisms by controlling rates of physiological processes. Demographic effects of warming, however, are determined by the expression of these physiological effects through predator–prey and other species interactions. Using field observations and controlled experiments, we measured how increasing temperatures in the Arctic affected development rates and mortality rates (from predation) of immature Arctic mosquitoes in western Greenland. We then developed and parametrized a demographic model to evaluate how temperature affects survival of mosquitoes from the immature to the adult stage. Our studies showed that warming increased development rate of immature mosquitoes (Q₁₀ = 2.8) but also increased daily mortality from increased predation rates by a dytiscid beetle (Q₁₀ = 1.2–1.5). Despite increased daily mortality, the model indicated that faster development and fewer days exposed to predators resulted in an increased probability of mosquito survival to the adult stage. Warming also advanced mosquito phenology, bringing mosquitoes into phenological synchrony with caribou. Increases in biting pests will have negative consequences for caribou and their role as a subsistence resource for local communities. Generalizable frameworks that account for multiple effects of temperature are needed to understand how climate change impacts coupled human–natural systems.     

Insecticide susceptibility status in two medically important mosquito vectors,Anopheles gambiae,and Culex quinquefasciatus to three insecticides commonly used in Niger State,Nigeria

High resistance ability on insecticides among major mosquito vectors of diseases in Nigeria is of growing concern for severe control strategies. The objective of this study was to assess the susceptibility status of females Anopheles gambiae and Culex quinquefasciatus complexes mosquitoes to permethrin (21.5 μg/bottle-pyrethroids), propoxur(12.5 μg/bottle-carbamate) and malathion (50 μg/bottle organophosphate), in Niger State, North-Central, Nigeria. Anopheline and Culecine larvae were collected from the larval habitats of the studied sites (Bosso, Katcha, Lapai, and Shiroro) larvae and pupae were identified guided by standard keys and reared to adults in troughs. Insecticide susceptibility bioassays were performed according to the CDC bottle bioassay standard operating procedures on 3 days old, sugar-fed female Anopheles and Culex mosquitoes. Post-exposure mortality after 24hr and knockdown values for KDT₅₀ were calculated. Knock-down at 1-hour insecticide exposure ranged (84–96 %) permethrin, (94–100 %) propoxur and (100 %) malathion for An. gambiae and (86–97 %) permethrin, (92–100 %) propoxur and (96–100 %) malathion for Cx. quinquefasciatus. Mortality, after 24hr post-exposure was 100 % in malathion, indicating the high effect of the insecticide. Tested samples were found potentially resistant to permethrin recorded against mosquitoes collected from all study sites, in two locations of the study sites to propoxur and one location site to malathion. All the tested mosquitoes were found to be potentially resistant to permethrin, however, mosquitoes tested in Katcha and Shiroro resist potentially to propoxur. Except, Culex quinqufasciatus from Lapai that partially resist malathion, all the tested mosquitoes were found to be susceptible to malathion, across the study sites.     

Toxicity of 1,3-dichloropropene and fosthiazate to wireworms (Agriotes spp.)

Wireworms (Agriotes spp.) are sporadic but increasingly important pests of potatoes, sugar beet and cereals. Whilst effective chemical control is possible, the granular organophosphates normally require high rates of application and the seed dressings containing lindane (gamma‐HCH) have been withdrawn from use. The soil fumigant 1,3‐dichloropropene (1,3‐D as Telone II) and the granular nematicide fosthiazate (Nemathorin 10G) are currently used for the control of potato cyst nematodes. We investigated the effects of both of these chemicals on wireworms. Air‐vapour phase toxicities for 1,3‐D against wireworm were LD₅₀ 2.74 mg.litre.day and LD₉₉ 5.05 mg.litre.day. The in vitro soil phase toxicity was LD₉₉ 8.15 mg.litre.day. 1,3‐D soil phase activity against wireworm may be associated more with air‐vapour phase than a soil‐water phase activity. In glasshouse experiments 16.0 mg.litre.day of 1,3‐D gave 75% control. Fosthiazate, which is applied at approximately 2 μg g^?1 of soil for potato cyst nematode control, achieved an LC₅₀ at 3.20 μg g^?1. In both in vitro and glasshouse studies 1,3‐dichloropropene showed high toxicity to wireworm at dosages below the current commercial application rate for potato cyst nematode control and fosthiazate also showed useful efficacy. These chemicals may therefore prove to be valuable additional tools for limiting initial wireworm plant damage or reducing wireworm populations.     

Miticide bioassays with spider mites (Acari: Tetranychidae): effect of test design and sample size on the precision of lethal concentration estimates

The effect of interval space between the concentration (symmetric or geometric), number of concentrations and overall sample sizes were investigated using a Petri dish bioassay, the miticide propargite and two spider mites species. The precision (width of the 95% confidence intervals) of the LC₅₀ and LC₉₀ estimates was shown to be influenced by the test design and total sample size The results suggest that a symmetric five-concentration design using a minimum total sample size of 480 mites is required to produce reliable LC estimates using the Petri dish method. Asymmetric designs did not increase the reliability of LC estimates. When less than 480 test subjects are available, a symmetric three-concentration design would give adequate LC estimates, but the precision would be less than with a five-concentration design.     

Dosage differential effects of permethrin impregnated into bednets on pyrethroid resistant and susceptible genotypes of the mosquito Anopheles stephensi

Abstract Effects of bednets impregnated with permethrin 200 mg and 500mg/m² on pyrethroid resistant and susceptible strains of Anopheles stephensi and their F hybrid progeny were studied, using free-flying female mosquitoes of these three genotypes, in a room with a human subject under a polyester net, having one of his arms in contact with the treated netting. Unexpectedly an apparently higher feeding rate, but lower knockdown and mortality rates, of mosquitoes were obtained for each of the three genotypes with the higher concentration of 500mg/m² compared with the lower dose of 200mg/m². At the lower dose there was 100% mortality 24 h after exposure of all three genotypes, suggesting that there would not be selection for resistance at this dose. However, at the higher dose there was significantly higher mortality of the susceptible strain than of the F hybrids, suggesting incomplete recessiveness of this resistance and that there would therefore be effective selection for resistance by this dose.
When female mosquitoes were confined in bioassay cones on treated netting, the resistant strain of An.stephensi showed significantly less irritability (scored as the time until first flight take-off) in response to each dose, as compared with the susceptible strain and F, hybrids. The higher dose provoked more irritation of each genotype; this could explain the greater knockdown and mortality rates of mosquitoes exposed to the lower dose which was less irritating and hence more effectively insecticidal. Thus a dose of 200mg/m² is preferable to 500mg/m² for malaria vector control.     

Investigation on the insecticidal efficacy of novel pellet formulation against Callosobruchus maculatus (F.) (Col.: Bruchidae) in three different heights and compared with phosphine

Applying essential oils, fumigant toxicity in stored products pests control has sharpened recently. Since these products have low penetration power and vapour pressure, their use in crop depth is restricted. The aim of this work was using controlled release technology to solve this problem. In this research, 1,8-cineole-based pellets were prepared by dry mixing method and physical load of 1,8-cineole on strach, which followed by pressing the mixture, using pellet maker apparatus, to form pellets. Insecticidal efficacy of produced pellets was investigated against adults (1–3?days old) Callosobruchus maculatus F. (Col.: Bruchidae) compared with phostoxin under 28?±?2?°C and darkness in laboratory condition. LC₅₀ and LC₉₅ of pellets against C. maculatus in 24?h were 0/017 and 0/050?ml active ingredient per L air, respectively. LC₅₀ and LC₉₅ of phosphine pellets against C. maculatus in 24?h were 0/124 and 1/852?ml active ingredient per L air, respectively.