Sublethal effects of buprofezin on development,reproduction, and chitin synthase 1 gene (SfCHS1) expression in the white-backed planthopper,Sogatella furcifera (Hemiptera: Delphacidae)

The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), is a major rice pest in some Asia-Pacific countries. Buprofezin is an insect growth regulator with relatively low mammalian toxicity but high efficacy to many rice pests. In this study, we estimated the toxicity of buprofezin against 3rd-instar nymphs of S. furcifera using the rice-stem dipping method. The results showed that the LC₅₀ of buprofezin to 3rd-instar nymphs were 0.89?mg/L. When 3rd-instar nymphs were exposed to the LC₁₀ and LC₂₅ (0.10 and 0.28?mg/L) of buprofezin, the duration of juvenile development was significantly prolonged in the F₀ and F₁ generations. The fecundity (eggs per female) of the F₁ females was reduced by 5.29% and 12.34%, respectively, in addition to the survival rate, emergence rate, copulation rate, and hatchability were decreased by treatment with buprofezin at LC₁₀ and LC₂₅, compared with the control group. The relative fitness of S. furcifera in LC₁₀ and LC₂₅ treatments was reduced by 47% and 63%, respectively. Furthermore, real-time quantitative PCR analyses revealed increased the expressions of SfCHS1 and its two variants following the exposure of nymphs to buprofezin. Increased these genes mRNA levels associated with reduced chitin biosynthesis may result from the inhibition of chitin synthase activity, and thereby leading to a higher mortality of S. furcifera. Overall, sublethal concentrations of buprofezin suppressed the population growth of S. furcifera.     

Genetic variation in developmental times among four pure lines exhibiting specific wing form and body color in the brown planthopper, <Emphasis Type="Italic">Nilaparvata lugens</Emphasis> (Hemiptera: Auchenorrhyncha)

Developmental times were compared among four pure lines of wing-dimorphic Nilaparvata lugens generated by successive selections for the following designated characteristics: blackish short-winged (BS), blackish long-winged (BL), yellowish brown short-winged (YS) and yellowish brown long-winged (YL). When the nymphs were reared on rice seedlings at low density, the developmental time was in the order of BS = BL < YS = YL, while with an increase in rearing density, the time lengthened markedly in long-winged lines but only slightly in short-winged lines, rearranging the order to BS < BL = YS < YL. Among F₁ progeny of BS × YL, the developmental time in short-winged phenotypes was the same as those of BS lines at any of the densities tested, but the long-winged phenotypes emerged as adults at intermediate time between BS and YL lines at high density. This method of inheritance of developmental time and the differences in the duration observed among the four pure lines suggest that the genes regulating wing form and body color expression are also involved in the regulation of developmental time.     

Developmental control of ultrasound sensitivity by a juvenile hormone analog in crickets (Teleogryllus oceanicus)

Cricket ears are sensitive to ultrasound as well as to lower, cricket-like sound frequencies. Ultrasound stimuli evoke negative phonotaxis in flying crickets, a behavior that has been interpreted as a defensive response against predation by echolocating bats. A recent study on a wing-dimorphic species, Gryllus texensis, showed that short-winged individuals, which are incapable of flight, are less sensitive to ultrasound, but not to lower sound frequencies, than their long-winged counterparts. The developmental decision to develop as a long- or short-winged individual is made during the last two larval instars, and there is some evidence suggesting that juvenile hormone (JH) has an instructive role, such that high levels of JH result in short-winged individuals. We show that treatment of last-instar larvae of a monomorphic long-winged species, Teleogryllus oceanicus, with a JH analog causes a decrease in sensitivity to ultrasound, but not to the lower sound frequency used for intraspecific communication.     

Effects of triflumezopyrim on the reproduction of brown planthopper,Nilaparvata lugens

The brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), is a notorious pest on rice in Asia and has evolved serious resistance to traditional chemical insecticides in recent years. Triflumezopyrim, a newly commercialized mesoionic insecticide, exhibited an excellent control effect on sucking insects, including N. lugens. However, the effects of triflumezopyrim on the reproduction of N. lugens have not yet been fully elucidated. In this study, we investigated the impacts of different concentrations of triflumezopyrim (LC₁₀, LC₅₀ and LC₉₀) on the reproduction and the reproduction related genes of N. lugens exposure to the insecticide via systemic and contact route. The results indicated that the preoviposition periods of N. lugens females in the LC₅₀ and LC₉₀ triflumezopyrim-treated groups (♀ t × ♂ t) were prolonged in contact toxicity treatment, compared with control (acetone treatment). The fecundities for three pair combinations (♀ c ×♂ t, ♀ t ×♂ c and ♀ t ×♂ t) treated with LC₅₀ and LC₉₀ concentrations of triflumezopyrim showed a significant decrease compared to water/acetone-treated control via contact and systemic route. No significant effects of LC₁₀ triflumezopyrim on preoviposition period and fecundity were found in contact and systemic toxicity treatments. However, the triflumezopyrim did not influence the egg hatchability. By microscope observation, the LC₅₀ and LC₉₀ triflumezopyrim impended the ovarian development in females. qRT-PCR analysis showed that the vitellogenin (NlVg) relative expression level of female adults exposed to LC₅₀ and LC₉₀ triflumezopyrim decreased by 30.3 – 39.5% in two toxicity treatments. The titers of another reproduction related hormones juvenile hormone III (JH III) in LC₅₀ and LC₉₀ triflumezopyrim-treatments were 27.4% and 25.8% lower than control in contact toxicity treatment and 27.08% and 37.18% lower than control in systemic toxicity treatment. In summary, these results suggested that the median lethal and high lethal concentrations of triflumezopyrim inhibited the reproduction and reduced the expression of NlVg and JH III in N. lugens. This study provided a reference for the efficient and scientific utilization of triflumezopyrim in the field.     

Juvenile hormone-mediated reproduction induced by a sublethal concentration of imidacloprid in Cyrtorhinus lividipennis (Hemiptera: Miridae)

The Hemipteran predator, Cyrtorhinus lividipennis, feeds on the eggs and nymphs of rice planthoppers and leafhoppers. We previously demonstrated that sublethal concentrations of imidacloprid stimulated the reproduction of C. lividipennis. Considering the essential roles of juvenile hormone (JH) in insect reproduction, we speculated that sublethal concentrations of imidacloprid may stimulate the reproduction of C. lividipennis by regulating JH level. To test this, we cloned C. lividipennis JH acid methyl transferase (ClJHAMT) and JH esterase (ClJHE), which are responsible for JH biosynthesis and degradation genes, respectively. We then knocked down ClJHAMT by injecting dsRNA into C. lividipennis nymphs and found that emerging female adults exhibited 88.8% lower expression of the vitellogenin gene (ClVg) and the number of eggs was reduced by 41.5% as compared with controls. Silencing ClJHE increased ClVg mRNA expression by 275.0% but did not affect fecundity. A sublethal concentration of imidacloprid (LC₂₀) increased the JH titer in females by 35.3% and 60.6% at 24 and 48 h post-emergence, respectively. In treatments containing both imidacloprid and dsJHAMT, the silencing of CLJHAMT reduced the number of eggs produced by adult females by 21.4% as compared to the control (imidacloprid + dsGFP). Our results indicated that sublethal concentration of imidacloprid may induce C. lividipennis reproduction by upregulating JH level via JHAMT. The finding could provide valuable information for improved integration of C. lividipennis and insecticides in pest management.     

Relative contribution of genetic and environmental factors to determination of wing morphs of the brown planthopper Nilaparvata lugens

Wing dimorphism is a fascinating feature of the ability of insects to adapt to environments. The brown planthopper (BPH) Nilaparvata lugens, a serious pest of rice, can switch between the long- and short-winged morphs. It has been known that environmental factors can affect the wing morph of BPH. However, it is still unclear whether the effect of environment is dependent on BPH genetic backgrounds or not. In the present study, we established the pure-bred lineages of short- and long-winged BPHs via multigenerational selection, and we found that survival and fecundity were similar between these 2 lineages. Wing morphs of the pure-bred lineages were almost fully dependent on genetics, but independent of the environmental factors, nymphal density and rice plant stage, 2 key factors affecting BPH wing morphs. In the unselected BPH population, short- and long-winged morphs were produced depending on those 2 environmental factors, indicating the contribution of environment to wing morph. In the wing-selected lineages, 4 developmental regulated genes of wing, NlInR1, NlInR2, NlAkt, and NlFoxo were expressed stably in the short-winged adults, but almost silenced in the long-winged adults. However, all these genes were expressed normally with a similar level in both the short- and long-winged adults in an unselected population except NlFoxo. The pure-bred lineages of long- and short-winged morphs exhibited different expression patterns of wing development-regulated genes, suggesting the genetic determination of wing morphs. Effects of environmental factors on wing morphs occurred only in the genetic mix population.     

Larvicidal potential of gold and silver nanoparticles synthesized using Acalypha fruticosa leaf extracts against Culex pipiens (Culicidae: Diptera)

Plant secondary metabolites have been recently used for the synthesis of different nanoparticles. The present investigation aimed at evaluating the effect of gold (AuNPs) and silver (AgNPs) nanoparticles synthesized using Acalypha fruticosa leaf extracts to control the mosquito Culex pipiens. The A. fruticosa AuNPs and AgNPs spectra displayed their maximum absorption at 550 nm and 440 nm, respectively. The infrared spectra revealed different functional groups related to different chemical compounds. The larval mortality of aqueous leaf extract of A. fruticosa was 499.54 ppm (LC₅₀) and 1734.06 ppm (LC₉₀) after 24 h of treatment. This study revealed that AuNP (LC₅₀, 30.2 and LC₉₀, 104.83 ppm) and AgNP (LC₅₀, 52.86 and LC₉₀, 157.227 ppm) preparations were highly effective compared to the A. fruticosa extract alone and also more affordable, as a smaller amount was required. The present findings show the potential larvicidal effect of the synthesized AuNPs and AgNPs for the control of mosquito-mediated disease transmission.     

Sublethal effects of beta-cypermethrin on the bird cherry-oat aphid Rhopalosiphum padi (Hemiptera: Aphididae)

Rhopalosiphum padi is a sap-sucking aphid and an important pest of wheat that causes considerable yield loss. Beta-cypermethrin, a synthetic pyrethroid pesticide, has a broad insecticide spectrum and is considered effective for aphid control, while its residual concentrations may have sublethal effects on R. padi. Here, the sublethal effects of beta-cypermethrin on R. padi were conducted under laboratory conditions. The acute toxicity test showed that LC₁₀, LC₂₀, and LC₂₅ of beta-cypermethrin to R. padi adults were 0.003, 0.031 and 0.079 mg L⁻¹, respectively. The pre-adult survival rate was significantly reduced by all three concentrations. LC₂₀ significantly extended the development duration of 1st instar nymphs, pre-oviposition period, and oviposition period of R. padi. The adult longevity was also reduced by LC₂₅. However, the fecundity did not differ between the beta-cypermethrin treatment and control. For life table parameters, both the finite rate (λ) and intrinsic rate of increase (r) decreased at LC₁₀ and LC₂₀, as well as the net reproductive rate (R₀) reduced at LC₁₀ and LC₂₅, while mean generation time (T) increased at LC₂₀. Thus, at the concentrations of beta-cypermethrin tested here, there were negative impacts on R. padi fitness by decreased pre-adult survival rate, λ, r, and R₀, and delayed the development of some stages and increased T.     

Effect of avermectin (AVM) on the expression of γ‐aminobutyric acid A receptor (GABAAR) in Carassius gibelio (Bloch, 1782)

This study describes the effect of avermectin (AVM) on the expression of γ‐aminobutyric acid A receptor (GABA_AR) in Carassius gibelio. To assess the specific expression of GABA_AR in the brain, gonads, liver, kidneys, heart, muscles, and skin of C. gibelio, the expression of GABA_AR α1 subunit (GABA_ARα1) was measured by Western blotting. To study the effects of AVM on the expression of GABA_AR, the median lethal concentration (LC₅₀) at 24, 48, and 96 h of AVM was determined and the expression of GABA_AR in the brain, liver, and kidneys of the corresponding C. gibelio evaluated by Western blotting and immunohistochemistry. The results show that GABA_AR was expressed in the brain, gonads, liver, kidneys, heart, intestines, muscles, and skin, while primarily distributed in the central nervous system and moderately distributed in peripheral tissues. The expression of GABA_AR in the brain, liver, and kidney tissues of C. gibelio was increased with the treatment of AVM at 24 h LC₅₀, but attenuated by the treatment of AVM at 48 h LC₅₀ and 96 h LC₅₀. This suggests a threshold effect of AVM.     

Lethal and sublethal effects of two new insecticides spirotetramat and flupyradifurone in comparison to conventional insecticide deltamethrin on Trichogramma evanescens (Hymenoptera: Trichogrammatidae)

The effects of three insecticides including deltamethrin, spirotetramat and flupyradifurone on pre-imaginal stages of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) were investigated using dipping method. The mean emergence rate of T. evanescens when exposed to the recommended field concentrations of deltamethrin, spirotetramat and flupyradifurone were 62.8, 84 and 86.1%, respectively while 94.3% of the wasps emerged in the control group. According to the concentration–response experiments, the LC₅₀ values of deltamethrin, spirotetramat and flupyradifurone were 262.9, 274.8 and 334.8 ppm, respectively. The results indicated that lethal (LC₅₀) and sublethal (LC₃₀) concentrations of three tested insecticides significantly reduced the fecundity and longevity of T. evanescens. However, LC₃₀ of spirotetramat and flupyradifurone didn’t influence the oviposition duration of the wasps when compared with the control group. The gross reproductive rate (GRR), intrinsic rates of increases (r), net reproductive rate (R₀), and finite rate of increase (λ) were significantly lower in all the treated wasps in comparison with control. However, the mean generation time (T) was not affected by the sublethal concentrations of tested insecticides. According to our findings, all insecticidal treatments have adverse effects on the population of T. evanescens, notwithstanding sublethal concentration of flupyradifurone followed by spirotetramat were more compatible with adults T. evanescens in comparison with deltamethrin. However, further studies under the field conditions are required to confirm the results.     

灰飞虱长、短翅型品系对高、低温的适应能力差异

【目的】灰飞虱Laodelphax striatellus种群存在长翅和短翅个体,其翅型分化受遗传和环境条件的影响。本研究旨在明确经连续定向选育的灰飞虱长、短翅型品系对高、低温的适应能力差异。【方法】在室内分别长期定向筛选63和65代建立灰飞虱长、短翅型品系,并在南京田间采集灰飞虱自然种群;分别在25℃, 30℃和35℃恒温条件下测定上述灰飞虱长、短翅型品系和自然种群的繁殖力、存活率和发育历期,测定若虫在5℃和-20℃下的存活率以及若虫和成虫的过冷却点,通过品系间存活率、发育历期、生殖力和过冷却点的比较分析,确定灰飞虱长、短翅型品系对高温和低温的耐受能力。【结果】在25℃, 30℃和35℃下,灰飞虱自然种群雌成虫的繁殖力均显著高于室内筛选后的长、短翅型品系,而长、短翅型品系雌成虫之间的繁殖力均无显著差异;长、短翅型品系的繁殖力在25℃和30℃之间均无显著差异,但自然种群在25℃下的繁殖力显著高于30℃条件下的繁殖力;35℃下长、短翅型品系基本无若虫产生。25℃下长翅型品系、短翅型品系和自然种群若虫的存活率无显著差异,但在30℃下,短翅型品系若虫的存活率显著低于自然种群,而与长翅型品系差异不显著;35℃下长、短翅型品系的若虫最长只能存活到3龄,且两品系间无显著差异,而自然种群可存活到5龄。25℃下,短翅型品系若虫的发育历期显著短于自然种群,而与长翅型品系无差异;但是在30℃下,短翅型品系若虫历期显著长于长翅型品系和自然种群。长翅型品系、短翅型品系和自然种群灰飞虱3-4龄若虫在5℃低温下的存活天数无显著差异,并且长翅和短翅型品系在-20℃极端低温下暴露10 min后其死亡率也无显著差异且均显著高于自然种群。3个品系(种群)成虫的过冷却点无显著差异,但5龄若虫的过冷却点表现为短翅型品系显著高于自然种群,而与长翅型品系无显著差异。【结论】经连续定向选育的灰飞虱长、短翅型品系对低温和高温的适应力基本相当,且低于自然种群。在高温条件下灰飞虱短翅型品系的发育速率低于长翅型品系。     

Optimization of the microemulsion formulation of curcuma oil and evaluation of its acaricidal efficacy against Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae)

The microemulsion formulation (hereafter formulation) of curcuma oil and its acaricidal efficacy against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae) were optimized in the laboratory to evaluate their spray effectiveness of oviposition inhibition and repellence. Ethovision XT6 was used to analyse the effects of the sublethal concentrations (LC₂₀) of curcuma oil and the formulation on the behaviors of T. cinnabarinus. The results showed that Tween-80 was the best surfactant, Isopropanol was the best co-surfactant and K_m = 2:1 was the best condition for the formulation. The prepared microemulsions are stable under conditions of centrifugation and incubation for extended periods. The results showed that the effect of the spray bioassays of the formulation against T. cinnabarinus continuously increased during the experiment, but for curcuma oil almost no longer increase observed when the exposure time went beyond 24 h. Moreover, compared with curcuma oil (LC₅₀ = 0.716%), the spray bioassay of the formulation (LC₅₀ = 0.035%) was stronger against T. cinnabarinus. The repellency of the formulation to T. cinnabarinus was stronger with increasing exposure time, but that of curcuma oil declined after 12 h of exposure. The mobile distance of T. cinnabarinus treated with the formulation continuously declined during the experiment but that due to the curcuma oil almost no longer declined when the treatment time reached 12 h. The maximum mobile frequency of T. cinnabarinus treated by curcuma oil and the formulation was recorded at 6 h and 12 h, respectively. Thus, the formulation is a promising candidate as a botanical acaricide of green vegetables.     

Mosquito larvicidal activity of Aloe vera (Family: Liliaceae) leaf extract and Bacillus sphaericus,against Chikungunya vector,Aedes aegypti

The bio-efficacy of Aloe vera leaf extract and bacterial insecticide, Bacillus sphaericus larvicidal activity was assessed against the first to fourth instars larvae of Aedes aegypti, under the laboratory conditions. The plant material was shade dried at room temperature and powdered coarsely. A. vera and B. sphaericus show varied degrees of larvicidal activity against various instars larvae of A. aegypti. The LC₅₀ of A. vera against the first to fourth instars larvae were 162.74, 201.43, 253.30 and 300.05 ppm and the LC₉₀ 442.98, 518.86, 563.18 and 612.96 ppm, respectively. B. sphaericus against the first to fourth instars larvae the LC₅₀ values were 68.21, 79.13, 93.48, and 107.05 ppm and the LC₉₀ values 149.15, 164.67, 183.84, and 201.09 ppm, respectively. However, the combined treatment of A. vera + B. sphaericus (1:2) material shows highest larvicidal activity of the LC₅₀ values 54.80, 63.11, 74.66 and 95.10 ppm; The LC₉₀ values of 145.29, 160.14, 179.74 and 209.98 ppm, against A. aegypti in all the tested concentrations than the individuals and clearly established that there is a substantial amount of synergist act. The present investigation clearly exhibits that both A. vera and B. sphaericus materials could serve as a potential larvicidal agent. Since, A. aegypti is a container breeder vector mosquito this user and eco-friendly and low-cost vector control strategy could be a viable solution to the existing dengue disease burden. Therefore, this study provides first report on the mosquito larvicidal activity the combined effect of A. vera leaf extract and B. sphaericus against as target species of A. aegypti.     

Sublethal effects of abamectin on the biological performance of the predatory mite, <Emphasis Type="Italic">Phytoseius plumifer</Emphasis> (Acari: Phytoseiidae)

Traditionally estimating pesticide effects by measuring only lethal effect may underestimate the total negative effect on beneficial arthropods and sublethal effects should be assessed to estimate the total effect of their applications. In this study, sublethal effect of the acaricide abamectin (Vermectin^® 1.8% EC, Giah, Iran) on the predatory mite Phytoseius plumifer (Canestrini &; Fanzago) (Acari: Phytoseiidae) fed on Tetranychus urticae Koch was assessed in laboratory conditions. The adult predators were exposed to the residues of the acaricide on fig leaves and the LC₅₀ value was determined based on a concentration–response analysis. The results showed that sublethal concentrations (LC₁₀, LC₂₀ and LC₃₀) of abamectin severely affected the fecundity and longevity of the treated females of P. plumifer. Furthermore, reproductive and life table parameters of the subsequent generation were affected. The results indicated that adverse effects of abamectin on population growth of P. plumifer were significant, so the results from this study can be used to develop approximate guidelines for the use of abamectin in order to minimize their impact on P. plumifer and related natural enemies.     

Sublethal effects of abamectin on the development,fecundity, and wing morphs of the brown planthopper Nilaparvata lugens

The brown planthopper Nilaparvata lugens negatively affects rice yield by sucking nutrients from the rice stem and spreading viruses. In this study, the effects of sublethal concentrations of abamectin on development, fecundity, and wing morphs of N. lugens were investigated. Treatment with sublethal concentrations of abamectin showed no significant effects on the developmental period of F₀ nymphs. Although LC₁₀ and LC₂₅ treatments resulted in 10% and 25% mortality, the LC₂₅ treatment significantly prolonged the lifespan of macropterous and brachypterous females. Abamectin-treated brachypterous females showed significantly lower fecundity than control females. Furthermore, abamectin treatment showed no significant effects on the developmental period of F₁ nymphs. However, LC₂₅ treatment significantly inhibited the fecundity of brachypterous F₁ females and significantly reduced the proportion of macropterous F₁ females and brachypterous F₁ males. LC₂₅ treatment showed no significant effects on the fecundity of macropterous F₁ females. Considering the proportion of macropterous and brachypterous F₁ females, the relative fitness of the macropterous F₁ nymphs in the control, LC₁₀, and LC₂₅ treatment groups was 1, 1.02, and 0.84, respectively, and that of brachypterous F₁ nymphs was 1, 0.79, and 0.93, respectively. Sublethal concentrations of abamectin inhibited N. lugens emergence. The present findings indicate the potential of abamectin for N. lugens field control.     

Insecticidal and developmental inhibitory properties of monoterpenes on Culex pipiens L. (Diptera: Culicidae)

Twelve monoterpenes were evaluated for larvicidal and adulticidal activities towards Culex pipiens. Geraniol and cuminaldehyde were the most toxic monoterpenes to larvae, with LC₅₀ values of 38.6 and 38.9 mg/l after 24 h of treatment, respectively, whereas cuminaldehyde was the most potent compound after 48 h of treatment, followed by geraniol and thymol. In fumigant toxicity experiments, (R)-carvone and geraniol were the most toxic monoterpenes against the adults at all three tested concentrations and after both 24 and 48 h. When tested at sublethal concentrations (0.5 LC₅₀), (R)-carvone, (S)-limonene and cuminaldehyde decreased hatchability, pupation and adult emergence and induced high larval mortality. Our results suggest that geraniol, cuminaldehyde and (R)-carvone are promising toxicants against Culex pipiens and could be useful in the search for new natural insecticides.     

Sublethal and transgenerational effects of six insecticides on Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

To clarify the effects of sublethal concentration of insecticide on the growth, development and reproduction of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), the sublethal and transgenerational effects of the LC₃₀ of six insecticides on adults and progeny (F₁ and F₂ generations) were studied using age-stage, two-sex life tables. Exposure to six insecticides had significant negative impacts on the life-history traits of B. dorsalis and led to reduced adult longevity and fecundity in F₀, a longer larval stage duration in F₁, and reduced fertility and survival. The intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R₀) were reduced in F₁, with the greatest reduction observed in the chlorpyrifos treatment. In the F₂ generation, the adverse effects were weakened, only the cyantraniliprole treatment had lower values than the control, and the fecundity of other treatments returned to normal. Obvious “hormesis” phenomena were not observed in any of the generations. Based on the population hazard index, chlorpyrifos had the best control effect in the early stage, and cyantraniliprole had the best control effect in the long term. These results indicate that the LC₃₀ of the six insecticides exert different transgenerational effects on the B. dorsalis population.     

Larvicidal and adulticidal activity of essential oils from plants of the Lamiaceae family against the West Nile virus vector,Culex pipiens (Diptera: Culicidae)

Culex pipiens mosquitoes are the most widely distributed primary vector of the West Nile virus worldwide. Many attempts for investigation of botanical pesticides to avoid the development of pesticide resistance to conventional synthetic pesticides that are recognized as a threat to the diversity of ecosystems. The study aimed to determine the components of three essential oils of Lamiaceae family, lavender (Lavandula angustifolia), peppermint (Mentha piperita L.), and rosemary (Rosmarinus officinalis L.) by gas chromatography-mass spectrometry (GC–MS) analysis. Furthermore, aimed to validate the insecticidal activities of these oils as larvicidal agents against the third instar larvae of Culex pipiens using five different concentrations (62.5, 125, 250, 500, and 1000 ppm) for each oil in five replicates and as an adulticidal agent against approximately three-day-old female adults of Cx. Pipiens using 0.5, 1, 2, 4, and 5% concentrations in three replicates. The results generally showed a dose-related response. At 1000 ppm, rosemary oil showed the highest larvicidal (100%) (LC₅₀, 214.97 ppm), followed by peppermint oil (92.00% mortality and LC₅₀ (269.35 ppm). Lavender oil showed the lowest efficacy with 87.20% mortality and LC₅₀ (301.11 ppm). At 5% oil concentration, the highest knockdown rate at 1 h was recorded for lavender oil (95.55%), followed by peppermint oil (88.89%) and lastly rosemary oil (84.44%). After 24 h, rosemary oil showed the lowest adult mortality rate (88.89%; LC₅₀, 1.44%), while lavender and peppermint oils both showed a 100% mortality rate, with (LC₅₀, 0.81% and 0.91%, respectively). The chemical constituents of the oils consisted of monoterpenes and sesquiterpenes that determined their insecticidal activities against the target insect stage. The study proposed that rosemary essential oil may be useful for the control of Cx. pipiens larvae as part of an integrated water treatment strategy, and lavender and peppermint oils may be used in an integrated plan for adult’s control.     

The larvicidal effect of neemazal T/S,clove oil and ginger oil on tomato leafminer,Tuta absoluta compared to coragen

The present study aimed to evaluate the toxicity and biochemical changes of Tuta absoluta 3^rd instar larvae affected by neemazal T/S, clove oil and ginger oil. These compounds were evaluated compared to the recommended pesticide, Coragen 20% SC. by means of sublethal concentrations, LC₂₅ and LC₅₀ under constant laboratory conditions. Results showed that neemazal T/S is more toxic than detected oils compared with higher toxicity of coragen with LC₅₀ values of 57.52, 159.94, 633.38 and 930.71 μg mL^?1 for coragen, neemazal, ginger oil and clove oil, respectively. There were highly significant differences between all treatments and untreated larvae. Neemazal possessed the greatest effect on activity level of most physiological parameters than selected oils. Larval content of digestive enzymes was decreased significantly 48 h after all treatments except for lipase, α-esterase and β-esterase (in case of coragen and clove oil). Also, total proteins, total carbohydrates, total lipids and total free amino acids take the same trend. Based on this study, these sublethal doses caused a significantly dose-dependent perturbation in determined components.     

Flipping the cyclooxygenase (Ptgs) genes reveals isoform-specific compensatory functions,

Two prostaglandin (PG) H synthases encoded by Ptgs genes, colloquially known as cyclooxygenase (COX)-1 and COX-2, catalyze the formation of PG endoperoxide H₂, the precursor of the major prostanoids. To address the functional interchangeability of these two isoforms and their distinct roles, we have generated COX-2>COX-1 mice whereby Ptgs2 is knocked in to the Ptgs1 locus. We then “flipped” Ptgs genes to successfully create the Reversa mouse strain, where knock-in COX-2 is expressed constitutively and knock-in COX-1 is lipopolysaccharide (LPS) inducible. In macrophages, flipping the two Ptgs genes has no obvious impact on COX protein subcellular localization. COX-1 was shown to compensate for PG synthesis at high concentrations of substrate, whereas elevated LPS-induced PG production was only observed for cells expressing endogenous COX-2. Differential tissue-specific patterns of expression of the knock-in proteins were evident. Thus, platelets from COX-2>COX-1 and Reversa mice failed to express knock-in COX-2 and, therefore, thromboxane (Tx) production in vitro and urinary Tx metabolite formation in COX-2>COX-1 and Reversa mice in vivo were substantially decreased relative to WT and COX-1>COX-2 mice. Manipulation of COXs revealed isoform-specific compensatory functions and variable degrees of interchangeability for PG biosynthesis in cells/tissues.